Investigation the existence and mechanism of Cu(II)-sulfamethoxazole co-pollution by road-deposited sediments in stormwater runoff

In recent years, the escalating attention on Pharmaceutical and Personal Care Products (PPCPs) and Heavy Metals in urban stormwater runoff highlights the critical role of Road-deposited sediments (RDS) as a significant carrier for pollutant occurrence and transport in runoff. However, existing research has overlooked the composite characteristics of PPCPs and Heavy Metals, hampering a holistic understanding of their transformation in diverse forms within runoff. This limitation impedes the exploration of their subsequent migration and conversion properties, thereby obstructing coordinated strategies for the control of co-pollution in runoff. This study focuses on the typical PPCP sulfamethoxazole (SMX) and heavy metal Cu(II) to analyze their occurrence characteristics in the Runoff-RDS system. Kinetics and isotherm studies reveal that RDS effectively accumulates SMX and Cu(II), with both exhibiting rapid association with RDS in the early stages of runoff. The accumulation of SMX and Cu(II) accounts for over 80 % and 70 % of the total accumulation within the first 240 min and 60 min, respectively. Moreover, as runoff pH values decrease, the initially synergistic effect between the co-pollutant transforms into an antagonistic effect. In the composite system, varying pH values from 2.0 to 6.0 lead to an increase in SMX accumulation from 4.01 mg/kg to 6.19 mg/kg and Cu(II) accumulation from 0.43 mg/g to 3.39 mg/g. Compared to the single system, the composite system capacity for SMX and Cu(II) increases by 0.04 mg/kg and 0.33 mg/g at pH 4.0. However, at pH 3.0, the composite system capacity for SMX and Cu(II) decreases by 0.21 mg/kg and 0.36 mg/g, respectively. Protonation/deprotonation of SMX under different pH conditions influences electrostatic repulsion/attraction between SMX and RDS. The mechanism of RDS accumulation of SMX involves Electron Donor-Acceptor (EDA) interaction, hydrogen bond interaction, and Lewis acid-base interaction. Cu(II) enrichment on RDS includes surface complexation reaction, electrostatic interaction, and surface precipitation. Complex formation enhances the accumulation of both SMX and Cu(II) on RDS in runoff. This study elucidates the co-occurrence characteristics and mechanisms of SMX and Cu(II) co-pollution in runoff systems. The findings contribute valuable insights to understanding the existence patterns and mechanisms of co-pollution, providing a reference for investigating the migration and fate of co-pollutant in runoff. Moreover, these insights could offer guidance for the development of effective strategies to mitigate co-pollution in rainwater.

Adsorption properties and mechanism of Cu(II) on virgin and aged microplastics in the aquatic environment

Microplastics (MPs) migrate by adsorbing heavy metals in aquatic environments and act as their carriers. However, the aging mechanisms of MPs in the environment and the interactions between MPs and heavy metals in aquatic environments require further study. In this study, two kinds of materials, polyamide (PA) and polylactic acid (PLA) were used as target MPs, and the effects of UV irradiation on the physical and chemical properties of the MPs and the adsorption behavior of Cu(II) were investigated. The results showed that after UV irradiation, pits, folds and pores appeared on the surface of aged MPs, the specific surface area (SSA) increased, the content of oxygen-containing functional groups increased, and the crystallinity decreased. These changes enhanced the adsorption capacity of aged MPs for Cu(II) pollutants. The adsorption behavior of the PA and PLA MPs for Cu(II) conformed to the pseudo-second-order model and Langmuir isotherm model, indicating that the monolayer chemical adsorption was dominant. The maximum amounts of aged PA and PLA reached 1.415 and 1.398 mg/g, respectively, which were 1.59 and 1.76 times of virgin MPs, respectively. The effects of pH and salinity on the adsorption of Cu(II) by the MPs were significant. Moreover, factors such as pH, salinity and dosage had significant effects on the adsorption of Cu(II) by MPs. Oxidative complexation between the oxygen-containing groups of the MPs and Cu(II) is an important adsorption mechanism. These findings reveal that the UV irradiation aging of MPs can enhance the adsorption of Cu(II) and increase their role as pollutant carriers, which is crucial for assessing the ecological risk of MPs and heavy metals coexisting in aquatic environments.

New Azo Derivative of β-Diketones and Its Cu(II), Co(II) Complexes: Synthesis, Theoretical Study and Biological Activity

The paper is focused on biological activity and theoretical study of the structure and properties of a new azo derivative of β-diketones and its complexes with some metals. The aim of our work was to study the structure and properties of the newly synthesized compound as well as to theoretically determine the possibility of complex formation with the Cu(II) or Co(II) ions. A compound with the same substituents R1=R2=CH3 was chosen for the study. A synthesized azo compound based on 4-amino antipyrine and its complexes with Cu(II), Co(II) in solution and solid phase is reported. The structures of these compounds have been testified by X-ray, IR and  NMR spectroscopy. The combined experimental and theoretical approach was used. To study the structure and properties of the synthesized compound, as well as its possible complex formation with the Cu(II), quantum-chemical calculations were carried out the 6-31G basis set and the electron density functional theory (DFT) method. These 3-(1-phenyl-2,3-dimethyl-pyrazolone-5) azopentadione-2,4 (PDPA) with Cu(II) and Co(II) complexes had effective inhibition against butyrylcholinesterase and acetylcholinesterase. IC50 values were found as 19.03, 3.64 μM for AChE and 28.47, 8.01 μM for BChE, respectively. Cholinesterase inhibitors work to slow down the acetylcholine's deterioration.

Enhanced copper removal by magnesium modified biochar derived from Alternanthera philoxeroides

Adsorption processes are being widely used by various researchers for the removal of heavy metals from waste streams and biochar has been frequently used as an adsorbent. In this study, a MgO-loaded biochar derived from Alternanthera philoxeroides (MAPB) was synthesized for the removal of Cu(II). Compared with other biochar absorbents, MAPB showed a relatively slow adsorption kinetics, but an effective removal of Cu(II) with a maximum sorption capacity of 1, 238 mg/g. The adsorption mechanism of Cu(II) by MAPB was mainly controlled by chemical precipitation as Cu2(OH)3NO3, complexation and ion replacement. Fixed bed column with MAPB packed in same dosage (1, 000 mg) and different bed depth (1.3, 2.6 and 3.9 cm) showed that the increased of bed depth by mixing MAPB with quartz sand could increase the removal of Cu(II). The fitted breakthrough (BT) models showed that mixing MAPB with support media could reduce the mass transfer rate, increase the dynamic adsorption capacity and BT time. Therefore, MAPB adsorbent act as a highly efficient long-term adsorbent for Cu(II) contaminated water treatment may have great ecological and environmental significance.

A new bodipy/pillar[5]arene functionalized magnetic sporopollenin for the detection of Cu(II) and Hg(II) ions in aqueous solution

In this study, a new bodipy/pillar[5]arene functionalized magnetic MS-Sp-P[5]-bodipy microcapsule sensor was prepared based on the use of environmentally friendly for the selective and sensitive detection of Cu(II) and Hg(II) ions in aqueous media. SEM results used in the characterization process of the materials synthesized at each stage confirmed the structural and morphological changes in the pore structure, while other characterization results (FT-IR and XRD) elucidated the role of pillar[5]arene compound and bodipy dye in the synthesis of magnetic microcapsule sensors. The colloidal solution of MS-Sp-P[5]-bodipy (water/ethanol)) showed two fluorescence bands centered at 402 and 540 nm. The detection limits of MS-Sp-P[5]-bodipy for Hg(II) and Cu(II) were calculated to be 0.06 µM and 2.27 µM, respectively (at 540 nm). The linear range of the magnetic sensor for Hg(II) and Cu(II) was found to be in the range of 1-150 µM and 10-150 µM, respectively. The experimental results (response time, pH, temperature, sensitivity and selectivity) demonstrated the applicability and potential of the prepared magnetic microcapsule sensor for the detection of Cu(II) and Hg(II) in water and tap water samples containing heavy metal ions.

Insights into adsorption behavior and mechanism of Cu(II) onto biodegradable and conventional microplastics: Effect of aging process and environmental factors

The widespread promotion attempt of biodegradable plastics is considered as an effective solution to address conventional plastic pollution. However, the interaction of microplastics (MPs) easily broken down from biodegradable plastics with the coexisting pollutants in aquatic environments has gained less attention. Herein, we investigated the effects of the aging process and environmental factors on copper (Cu(II)) adsorption behavior by biodegradable polylactic acid and conventional polystyrene MPs. Results demonstrated that the aging process significantly altered physicochemical properties of both types of MPs, and PLA showed less resistance to aging. The aged polylactic acid MPs (aged-PLA) exhibited the far highest Cu(II) maximum adsorption capacity (7.13 mg/g) mainly due to its abundant oxygen-containing functional groups (OCFGs), followed by pristine polylactic acid (PLA, 6.08 mg/g), aged polystyrene (aged-PS, 0.489 mg/g) and pristine polystyrene (PS, 0.365 mg/g). The adsorption kinetics of Cu(II) on PLA MPs were controlled by film and intraparticle diffusion, while film diffusion governed the Cu(II) adsorption onto PS MPs. In addition to roles of rougher surface structure, greater surface area and pore filling, the complexation of OCFGs and electrostatic interaction were critical to the adsorption mechanism of aged-PLA and aged-PS, and cation-π interaction was associated with adsorption of aged-PS. Moreover, the adsorption capacity of Cu(II) on aged MPs gradually grew with the increasing pH from 4 to 7. Besides, humic acid significantly promoted the adsorption of Cu(II) at a low concentration (0-20 mg/L) due to the formation of binary mixtures of MPs-HA but inhibited the adsorption at a high concentration (50 mg/L) because of its competitive effect, suggesting the dual roles of humic acid in the adsorption process. Overall, our findings provide a better understanding of the adsorption behavior of metals on biodegradable MPs and emphasize their non-negligible risk as carriers of contaminant.

Cu(II)-Mediated direct 18F-dehydrofluorination of phosphine oxides in high molar activity

BACKGROUND

The 18F/19F-isotope exchange method employing P(V)-centered prosthetic groups demonstrates advantages in addressing mild one-step aqueous 18F-labeling of peptides and proteins. However, the molar activity (Am) achieved through isotope exchange remains relatively low, unless employing a high initial activity of [18F]F-. To overcome this drawback, our work introduces a novel approach through a Cu-mediated direct 18F-dehydrofluorination of phosphine oxides. This method leverages the straightforward separation of the 18F-labeled product from the phosphine oxide precursors, aiming to primarily increase Am.

RESULTS

Through a 19F-dehydrofluorination efficiency test, Cu(OAc)2 was identified as the optimal oxidative metal salt, exhibiting a remarkable 100% conversion within one hour. Leveraging the straightforward separation of phosphine oxide precursors and phosphinic fluoride products, the Am of an activated ester, [18F]4, sees an impressive nearly 15-fold increase compared to the 18F/19F-isotope exchange, with the same initial activity of [18F]F-. Furthermore, this Cu(II)-mediated 18F-dehydrofluorination approach demonstrates tolerance up to 20% solvent water content, which enables the practical radiosynthesis of 18F-labeled water-soluble molecules under non-drying conditions.

CONCLUSIONS

The direct 18F-dehydrofluorination of phosphine oxide prosthetic groups has been successfully accomplished, achieving a high Am via Cu(II)-mediated oxidative addition and reductive elimination.

Lysosomal Cu(I)/Cu(II) Dependence of Antimicrobial Ability of Oyster Hemocytes and Regulation of Phagolysosomal System

Copper (Cu) is hyperaccumulated in oyster hemocytes and is an essential trace metal indispensable for diverse innate immune functions. However, the roles of Cu in oyster immune defense are still unclear. In this study, Cu exposure enhanced the phagocytosis of zymosan by increasing the number and length of filopodia, as well as mitochondrial ROS (mitoROS) production mainly in granulocytes, followed by semigranulocytes and agranulocytes. The intracellular calcium level increased to promote the phagosome-lysosome fusion after Cu exposure. The enhancement of phagosomal acidification and mitochondrion-phagosome juxtaposition were also found in granulocytes after Cu exposure. These results indicated that Cu could regulate the phagolysosomal system to enhance the antimicrobial ability of oyster hemocytes with the assistance of mitoROS. Furthermore, Cu(I) and Cu(II) were predominately located in lysosomes, and degranulation may provide a mechanism for exposing Cu to bacteria to prevent their survival and proliferation. Specifically, we showed that the newly formed Cu(I) arising from lysosomal Cu(II) moved to lysosomes and mitochondria in activated hemocytes to induce strong immune responses. The ability of the transformation of Cu(I) from Cu(II) followed granulocytes > semigranlocytes > agranulocytes, indicating that granulocytes played important roles in immune functions of oysters. Our results provided new insights into the understanding of antimicrobial effects of Cu in oyster hemocytes.

Design, spectral, molecular modeling, antimitotic, analytical and mechanism studies of phenyl isothiocyanate Girard's T derived metal complexes

The ligand N-{[(phenyl amino) thioxomethyl] hydrazino carbonyl methyl} trimethyl ammonium chloride (PTHAC) was prepared by the refluxing phenyl isothiocyanate and Girard-T (trimethyl ammonium-acethydrazide) in a molar ratio (1:1). The metal complexes derived from NiCl2.6H2O, CuCl2.2H2O and Co(CH3COO)2.6H2O were synthesized and purified. The PTHAC and its Cu(II), Co(II), and Ni(II) metal complexes(1-3) were characterized using a variety of various instrumental performances such as elemental analysis, magnetic moment, spectra (IR, UV-Vis, 1H NMR, mass) and thermal analysis (TGA and DTG).The results of element analysis, magnetic moment, spectra (IR, UV-Vis, 1H NMR, mass), and thermal (TGA and DTA) analyses provide the structures of the produced ligand and its (1-3) complexes. According to the spectroscopic results, PTHAC acts as an O, N and S tridentate donor, creating a mononuclear complex with copper(II), cobalt(II), and nickel(II) ions with an octahedral geometry. All of the atomic properties, including bond lengths, bond angles, HOMO, LUMO, dipole moments, and charges, have been determined. The cytotoxic activities of the PTHAC and the produced (1-3) complexes against breast carcinoma cells have been studied and correlated to the molecular modeling. When compared to the free ligand, CoII-L, and NiII-L, the CuII-L complex inhibits breast cancer cell growth more effectively. Furthermore, the PTHAC ligand was successfully applied for separation via flotation and spectrophotometric determination of Co(II) in several natural water, certified ore and pharmaceutical samples using oleic acid surfactant (HOL). At pH 6.5, PTHAC reacted with Co(II) to create a dark green (1:1) Co(II):PTHAC complex that was floated significantly using oleic acid (HOL) surfactant. The different experimental variable affecting the separation procedure e.g. pH, concentration of Co(II), HOL, PTHAC, temperature etc.…, were investigated. Co(II) had a linear range of (0.1-7.0) mgL-1. In the aqueous and scum layers, the molar absorptivities for the coloured complex are 0.14 × 104 and 0.16 × 105Lmol-1 cm-1, respectively. The LOD was 0.04 mgL-1, which is related to Sandell sensitivity of 3.7 × 10-3 µg cm-2 with a preconcentration factor of 200 and a RSD, % (n = 5) less than 4.2%. In addition, the mechanisms involved in the process of coordination of PTHAC with Cu(II), Co(II) and Ni(II) and the mechanism involved in the process of flotation of the PTHAC-Co(II) complex using HOL surfactant were elucidated.

Preparation of sulfur self-doped coal-based adsorbent and its adsorption performance for Cu2

The limited application of high-sulfur coal (HSC) and the increasing severity of copper pollution in solution are two pressing issues. To alleviate such issues, a sulfur self-doped coal-based adsorbent (HSC@ZnCl2) was obtained by pyrolysis (850 °C, 60 min holding time) of HSC and ZnCl2 with a mass ratio of 1:0.5. The results adsorption experiment revealed that the endothermic and spontaneous adsorption process was consistent with the Sips isothermal model (R2 = 0.992) and pseudo-second-order kinetic (R2 = 0.994), and that the adsorption process with a maximum adsorption capacity of 11.97 mg/g. Meanwhile, the adsorption of Cu2+ onto HSC@ZnCl2 was a result of the synergistic effects of various interactions, such as the complexation by oxygen-containing functional groups, electrostatic attraction and surface precipitation by ZnS on the adsorbent surface, and the process also included redox reaction. The findings of this work indicate that the preparation of sulfur self-doped coal-based adsorbent prepared from high-sulfur coal is a promising method for its large-scale utilization.

Nalidixic Acid and Fe(II)/Cu(II) Coadsorption at Goethite and Akaganéite Surfaces

Interactions between aqueous Fe(II) and solid Fe(III) oxy(hydr)oxide surfaces play determining roles in the fate of organic contaminants in nature. In this study, the adsorption of nalidixic acid (NA), a representative redox-inactive quinolone antibiotic, on synthetic goethite (α-FeOOH) and akaganéite (β-FeOOH) was examined under varying conditions of pH and cation type and concentration, by means of adsorption experiments, attenuated total reflectance-Fourier transform infrared spectroscopy, surface complexation modeling (SCM), and powder X-ray diffraction. Batch adsorption experiments showed that Fe(II) had marginal effects on NA adsorption onto akaganéite but enhanced NA adsorption on goethite. This enhancement is attributed to the formation of goethite-Fe(II)-NA ternary complexes, without the need for heterogeneous Fe(II)-Fe(III) electron transfer at low Fe(II) loadings (2 Fe/nm2), as confirmed by SCM. However, higher Fe(II) loadings required a goethite-magnetite composite in the SCM to explain Fe(II)-driven recrystallization and its impact on NA binding. The use of a surface ternary complex by SCM was supported further in experiments involving Cu(II), a prevalent environmental metal incapable of transforming Fe(III) oxy(hydr)oxides, which was observed to enhance NA loadings on goethite. However, Cu(II)-NA aqueous complexation and potential Cu(OH)2 precipitates counteracted the formation of ternary surface complexes, leading to decreased NA loadings on akaganéite. These results have direct implications for the fate of organic contaminants, especially those at oxic-anoxic boundaries.

Heat induced superfast diclofenac removal in Cu(II)-activated peracetic acid system: Mediation from non-radical to radical pathway

A Cu(II)/heat coactivated peracetic acid (PAA) system for enhancing diclofenac (DCF) degradation was proposed in this work. The superiority of this synergetic activation strategy for PAA, working reactive species, catalytic mechanism and effects of reaction parameters on DCF elimination in this system were simultaneously investigated. Based on our results, the DCF loss rate in Cu(II)-heat/PAA process at pH 8.0 was about 49.3 and 4.2 times of that in Cu(II)/PAA and heat/PAA processes, respectively. Increasing the reaction temperature to 60 оC not only motivated the conversion of Cu(II) to Cu(I) but also facilitated the one-electron transfer between Cu(I) and PAA, boosting the generation of radicals. Organic radicals (mainly CH3C(O)O• and CH3C(O)OO•) were evidenced to be the core oxidizing substances dominating in the destruction of DCF while hydroxyl radical (•OH) made a minor contribution in this system by electron paramagnetic resonance (EPR) method together with scavenging experiments. This study broads the eyes into enhanced PAA activation initiated by homogenous Cu(II), providing a simple but efficient tool to degrade micropollutants.

Histamine Recognition by Carbon Dots from Plastic Waste and Development of Cellular Imaging: Experimental and Theoretical Studies

The present work highlights the sustainable approach for the transformation of plastic waste into fluorescent carbon dots (CDs) through carbonization and then they were functionalized with L-cysteine and o-phenylenediamine. CDs which were characterized by different analytical techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to recognize Cu2+, Fe2+, and Hg2+ ions. The results show that the fluorescence emission was considerably quenched, and it is consistent with the interference and Jobs plots. The detection limit was found to be 0.35µM for Cu(II), 1.38 µM for Hg(II), and 0.51µM Fe(III). The interaction of CDs with metal ions enhances the fluorescence intensity detecting histamine successfully. It shows that plastic waste-based CDs can be applied clinically to detect toxic metals and biomolecules. Moreover, the system was employed to develop the cellular images using Saccharomyces cerevisiae cells with the support of a confocal microscope. Furthermore, theoretical studies were performed for the naphthalene layer (AR) as a model for C-dots, then optimized its structure and analyzed by using the molecular orbital. The obtained TD-DFT spectra coincided with experimental spectra for CDs/M2+/histamine systems.

Phosphate enhanced Cu(II)/peracetic acid process for diclofenac removal: Performance and mechanism

Since limitedly existing researches suggested Cu(II) had deficiently catalytic ability to PAA, in this work, we tested the oxidation performance of Cu(II)/PAA system on diclofenac (DCF) degradation under neutral conditions. It was found that overwhelming DCF removal could be obtained in Cu(II)/PAA system at pH 7.4 using phosphate buffer solution (PBS) compared to poor loss of DCF without PBS, and the apparent rate constant of DCF removal in PBS/Cu(II)/PAA system was 0.0359 min^-1, 6.53 times of that in Cu(II)/PAA system. Organic radicals (i.e., CH₃C(O)O• and CH₃C(O)OO•) were evidenced as the dominant contributors to DCF destruction in PBS/Cu(II)/PAA system. PBS motivated the reduction of Cu(II) to Cu(I) through chelation effect, and then the activation of PAA by Cu(I) was facilitated. Besides, due to the steric hindrance of Cu(II)-PBS complex (CuHPO₄), PAA activation was mediated from non-radical-generating pathway to radical-generating pathway, leading to desirably effective DCF removal by radicals. The transformation of DCF mainly experienced hydroxylation, decarboxylation, formylation and dehydrogenation in PBS/Cu(II)/PAA system. This work proposes the potential of coupling of phosphate and Cu(II) in optimizing PAA activation for organic pollutants elimination.

A fluorescent probe based on Cu(II) complex induced catalysis for repetitive detection of cysteine

Real-time imaging and monitoring of biothiols in living cells are essential for understanding pathophysiological processes. However, the design of the fluorescent probe that has accurate and repeatable real-time monitoring capabilities for these targets is highly challenging. In this study, we prepared a fluorescent sensor, Lc-NBD-Cu(II), which contains a N1, N1, N2-tris-(pyridin-2-ylmethyl) ethane-1,2-diamine as a Cu(II) chelating unit and a 7-nitrobenz-2-oxa-1,3-diazole fluorophore to detect Cysteine (Cys). Emission changes promoted by addition of Cys to this probe are distinctive and correspond to a range of processes including Cys induced loss of Cu(II) from Lc-NBD-Cu(II) to form Lc-NBD, Cu(I) oxidation to reform Cu(II), Cys oxidation to form Cys-Cys, Cu(II) binding to Lc-NBD to reform Lc-NBD-Cu(II), and competitive binding of Cu(II) to Cys-Cys. The study also shows that Lc-NBD-Cu(II) maintains high stability during the sensing process and that it can be utilized over a number of detection cycles. Finally, the findings show that Lc-NBD-Cu(II) can be utilized to repetitively sense Cys in living HeLa cells.

Molecular and Electronic Structures of Macrocyclic Compounds Formed at Template Synthesis in the M(II)-Thiocarbohydrazide-Diacetyl Triple Systems: A Quantum-Chemical Analysis by DFT Methods

Using density functional theory (DFT) B3PW91/TZVP, M06/TZVP, and OPBE/TZVP chemistry models and the Gaussian09 program, a quantum-chemical calculation of geometric and thermodynamic parameters of Ni(II), Cu(II), and Zn(II) macrotetracyclic chelates, with (NNNN)-coordination of ligand donor centers arising during template synthesis between the indicated ions of 3d elements, thiocarbohydrazide H₂N-HN-C(=S)-NH-NH₂ and diacetyl Me-C(=O)-C(=O)-Me, in gelatin-immobilized matrix implants was performed. The key bond lengths and bond angles in these coordination compounds are provided, and it is noted that in all these complexes the MN₄ chelate sites, the grouping of N₄ atoms bonded to the M atom, and the five-membered and six-membered metal chelate rings are practically coplanar. NBO analysis of these compounds was carried out, on the basis of which it was shown that all these complexes, in full accordance with theoretical expectations, are low-spin complexes. The standard thermodynamic characteristics of the template reactions for the formation of the above complexes are also presented. Good agreement between the data obtained using the above DFT levels is noted.

Differences in the spectral characteristics of dissolved organic matter binding to Cu(II) in wetland soils with moisture gradients

The environmental behavior of heavy metals in soil is significantly regulated by their binding with dissolved organic matter (DOM), which is affected by soil moisture contents. However, the mechanism of this interaction in soils with varying moisture is still not well understood. Using a combination of ultrafiltration, Cu(II) titration, and multispectral (ultraviolet-visible absorption, 3D fluorescence, Fourier transform infrared) analysis techniques, we studied the differences in the spectral characteristics and Cu(II) binding properties of soil dissolved organic matter (DOM) and its different molecular weight (MW) fractions with moisture gradients. We found that the abundance and spectral characters of soil DOM changed with increasing soil moisture, i.e., the increase in abundance while the decrease in aromaticity and humification index. The components of DOM, shown by Fluorescence region-integration (FRI) analysis, also changed, with an increase in the proportion of protein-like substances and a decrease of humic-like and fulvic-like substances. The overall Cu(II) binding potential of soil DOM diminished with increasing soil moisture, as indicated by the fluorescence parallel factor (PARAFAC) analysis. This is aligns with the changes in DOM composition, as the humic-like and fulvic-like fractions exhibited higher Cu(II) binding potential compared to the protein-like fractions. The low MW fraction of the MW-fractionated samples showed a stronger binding potential for Cu(II) compared to the high MW fraction. Finally, the active binding site of Cu(II) in DOM, as revealed by UV-difference spectroscopy and 2D-FTIR-COS analysis, decreased with increasing soil moisture, with the order of preferentially functional groups shifting from OH, NH, and CO to CN and CO. This study emphasizes the impact of moisture variations on the characteristics of DOM and its interaction with Cu(II), providing insight into the environmental fate of heavy metal contaminants in soil in areas with alternating land and water conditions.

Role of molecular weight-dependent spectral properties in regulating Cu(II) binding by dissolved organic matter from different sources

The complexation of metals with dissolved organic matter (DOM) under different compositions and molecular weights (MWs) will result in different environmental fate and toxicity, but the specific role and impact of DOM MWs remain less well understood. This study explored the metal binding characteristics by DOM with different MWs from different sources, including sea, river, and wetland waters. The results of fluorescence characterization showed that the >1 kDa high-molecular-weight (HMW)-DOM were mainly from terrestrial sources while the low-molecular-weight (LMW)-DOM fractions were mostly from microbial sources. Based on UV-Vis spectroscopic characterization, the LMW-DOM contained more unsaturated bonds than its HMW counterpart, and the substituents are generally dominated by polar functional groups. Summer DOM had more unsaturated bonds and a higher metal binding capacity than winter DOM. Furthermore, DOM with different MWs had significantly different Cu binding properties. In addition, Cu binding with microbially derived LMW-DOM mainly caused the change in the peak at 280 nm, while binding with terrigenous HMW-DOM resulted in the change of the 210 nm peak. Compared with the HMW-DOM, most of the LMW-DOM had stronger Cu-binding ability. Correlation analysis indicates that metal binding ability of DOM mainly depends on its concentration, number of unsaturated bonds and benzene rings, and types of substituents during interactions. This work provides an improved understanding of the metal-DOM binding mechanism, the role of composition- and MW-dependent DOM from different sources, and thus the transformation and environmental/ecological role of metals in aquatic systems.

Red-to-blue colorimetric probe based on biomass carbon dots for smartphone-integrated optosensing of Cu(II) and L-cysteine

We constructed a smartphone-integrated optosensor with inexpensive, reversible, environmental friendly, and rapid adsorption to detect Cu(II) and L-cysteine (L-Cys). The key part of this study was to prepare a red-to-blue colorimetric probe from herbaceous andrographis paniculata using one-pot polymerization at room temperature. When Cu(II) existed, the red fluorescence on the surface of the core-shell probe was quenched, while the blue fluorescence of the core did not respond, because the colorimetric probe interacted with the Cu(II) on the surface of red CDs. After L-Cys added, it interacted with the Cu(II) to strip it from the surface of red CDs, resulting in the recovery of fluorescence response. Under optimal conditions, the detection limits of this method for Cu(II) and L-Cys were 71 nM and 12 nM, respectively. Further, the red-to-blue colorimetric probe was integrated into smartphone with a software application to convert fluorescent color images into specific red (R), green (G), and blue (B) values. The spiked recovery of Cu(II) and L-Cys in lake water was verified the feasibility of the developed optosensors with a recovery of 98.2-101.6 % and 103.3-121.6 %. This method for detecting Cu(II) and L-Cys can not only recognize metal ions from actual samples, but also effectively protect CDs from quenching and restore fluorescence.

Enhanced activity of Fe/Mn nanoparticles using a response surface methodology and mechanism for removing oxytetracycline and copper ion

As feed additives, oxytetracycline (OTC) and copper ion (Cu(II)) are often detected in livestock and poultry farming wastewater. To address this issue, firstly, the synthesis conditions of Fe/Mn nanoparticles (Fe/Mn NPs) were initially optimized using a response surface methodology (RSM) to yield highly active Fe/Mn NPs, where the application of RSM significantly increased the Fe/Mn NPs' efficiency in removing co-contamination OTC and Cu(II),respectively, from 45.8 to 86.2% and 14.9-67.2%. Secondly, scanning electron microscope and Nitrogen adsorption-desorption isotherms results showed that Fe/Mn NPs were composed of elliptic particles between 20 and 40 nm, a specific surface area of 59.5 m² g^-1, and a mean pore diameter of 5.27 nm. Fourier infrared spectrometer and X-ray photoelectron spectroscopy analysis revealed that amino, carboxyl and hydroxyl functional groups existed on the surface. Zeta potential indicated that Fe/Mn NPs maintained a high negative charge density between pH 1 and 11. These surface properties possessed by the green synthesized Fe/Mn NPs resulted in high adsorption efficiency for co-contamination OTC and Cu(II). Based on this, a removal mechanism based on a combination of complex-bridging effect, pore-filling, hydrogen bonding, surface complexation, ion exchange and electrostatic attraction was proposed. Finally, the assessment of Fe/Mn NPs used in swine wastewater demonstrated that both 99.9% OTC and 55.6% Cu(II) were removed.

Transition Metal Complexes of Thiosemicarbazides, Thiocarbohydrazides, and Their Corresponding Carbazones with Cu(I), Cu(II), Co(II), Ni(II), Pd(II), and Ag(I)-A Review

This review focuses on some interesting and recent applications of transition metals towards the complexation of thiosemicarbazides, thiocarbohydrazides, and their corresponding carbazones. We started the review with a description of the chosen five metals, including Cu[Cu(I), Cu(II], Co(II), Ni(II), Pd(II), and Ag(I) and their electronic configurations. The stability of the assigned complexes was also discussed. We shed light on different routes describing the synthesis of these ligands. We also reported on different examples of the synthesis of Cu(I), Cu(II), Co(II), Ni(II), Ag(I), and Pd(II) of thiosemicarbazide and thiocarbohydrazide complexes (until 2022). This review also deals with a summary of the fruitful use of metal complexes of thiosemicarbazones and thiocarbazones ligands in the field of catalysis. Finally, this recent review focuses on the applications of these complexes related to their biological importance.

New insight into the enhanced ozonation of malodorous compounds by Cu(II): Inhibiting the formation of free radicals to promote ozone utilization

Metal-enhanced ozonation can greatly improve the decay of organic matter; however, whether this method benefits the decay of malodorous compounds or not and the possible mechanism are not well understood. In this study, nine typical malodorous compounds were selected to reveal that Cu(II)-enhanced ozonation can greatly promote the decay of fatty amines because of the direct ozone oxidation, which was enhanced to promote ozone utilization. Moreover, trace Cu(II) can amplify the observed rate constants of dimethylamine and trimethylamine for 48.9% and 155.7%, respectively, and Cu(II) dosage was the determining factor using response surface methodology to investigate the interactions between initial pH, Cu(II) dosage and ozone dosage. These results demonstrated that the formation of ^•OH and O₂^•- was inhibited rather than promoted, which was quite different from some previously reported Cu(II)-enhanced ozonation counterparts. Moreover, the enhanced effect of trace Cu(II) was exhibited in both single and complex malodorous compounds. The conversion pathway of nitrogen and sulfur elements was clarified, with the targeted mineralization of nitrogen of nitrogen-containing malodorous compounds into NO₃-N and the odor characteristics of sulfur-containing malodorous compounds disappeared. These findings provided new insight for utilizing metal ions to enhance the direct ozone oxidation capacity of malodorous compounds.

Hen lysozyme fibrillogenesis, molten globule intermediate and effect of copper salts

The amyloid fibres have been related to many diseases. The molten globule intermediate has been proposed to form part of the folding pathway of many proteins. In the present study, we investigated the mechanism of amyloid-fibres formation of hen egg-white lysozyme (HEWL) incubated in a potassium phosphate buffer, pH 11.8, 100 mM, at 37 °C for 30 h, and evaluated the influence of Cu(II) present in two salts (CuSO₄ and CuCl₂) during fibrillogenesis. Co-incubation and post-incubation of lysozyme with copper salts reduced the fluorescence signal of thioflavin T with an increment in the intrinsic fluorescence of the protein. The ANS fluorescence test showed that incubation of HEWL for 6 h generated a molten globule intermediate state that formed amyloid fibres when incubation was carried out for a 30-h timespan. Dynamic light scattering showed a heterogeneous population of states in samples incubated in the absence or the presence of salts during the fibrillation process. The existence of a reducing potential was verified during the formation of HEWL amyloid fibres with the bathocuproine disulphonate test. Transmission electron microscopy confirmed the presence and absence of fibres in solutions incubated with and without Cu(II). This work demonstrated that lysozyme formed amyloid fibres at 37 °C and copper inhibited its formation.Communicated by Ramaswamy H. Sarma.

Anticancer potential of Cu(II)prolinedithiocarbamate complex: design, synthesis, spectroscopy, molecular docking, molecular dynamic, ADMET, and in-vitro studies

Breast cancer continues to be a major health issue for women all over the world. Cancer medications like cisplatin, which are widely used, still have negative side effects. The novel complex was created as a potential anticancer medication candidate that is both effective and safe, with few side effects. The Cu(II) complex using the prolinedithiocarbamate ligands was synthesized in situ. The Cu(II) complexes Characterization by UV-Vis, FT-IR spectroscopy and melting point determination, conductivity, and HOMO-LUMO were studied. Computational NMR spectrum analysis was performed. The interaction of Cu(II)prolineditiocarbamate complex with cancer cell target protein (MCF-7) was confirmed by molecular docking and molecular dynamic. The pharmacokinetic/ADMET properties were also performed on the complex. Results of the cytotoxic complex test against cancer cells (MCF-7) undergoing apoptosis with an IC50 value of 13.64 µg/mL showed high anticancer activity in MCF-7 cancer cells. The in-vivo data for Cu(II)prolineditiocarbamate complex was predicted using the Protox online tool with an LD50 value of 2500 mg/kg and belonging to the GHS toxicity class 5, which means the compound has a low acute toxicity effect. The Cu(II) prolineitiocarbamate complex may pave the way for the development of essential metal-based chemotherapy for the treatment of breast cancer.Communicated by Ramaswamy H. Sarma.

Capturing effects of filamentous fungi Aspergillus flavus ZJ-1 on microalgae Chlorella vulgaris WZ-1 and the application of their co-integrated fungi-algae pellets for Cu(II) adsorption

Using filamentous fungi to capture unicellular microalgae is an effective way for microalgae recovery in water treatment. Here, fungi Aspergillus flavus ZJ-1 and microalgae Chlorella vulgaris WZ-1 isolated from a copper tailings pond were used to study the capture effect of ZJ-1 on WZ-1. The highest capture efficiency (97.85%) was obtained within 6 h under the optimized conditions of 30 °C, 150 rpm, fungi-algae biomass ratio of 2.24:1, and initial pH of 9.24 in microalgae medium. The formed fungi-algae pellets (FAPs) were further used to remove Cu(II) from aqueous solution. Results showed that the FAPs formed at different capture times all adsorbed Cu(II) well, and the PAFs formed within 2 h (PAFs_2 h) exhibited the highest Cu(II) adsorption capacity (80.42 mg·g^-1). SEM images showed that Cu(II) caused a change in the internal structure of PAFs_2 h from loose to compact, the mycelium shrunk, and the microalgal cells were concave. Cu(II) adsorption by PAFs_2 h was well conformed to the pseudo-second-order kinetics and the Langmuir isotherm (123.61 mg·g^-1 of theoretically maximum adsorption capacity). This work opens a way for applying FAPs in the remediation of heavy metal-contaminated wastewater, and the metal adsorption effect was determined by the capture amount of microalgae.

Adsorption Characteristics for Cu(II) and Phosphate in Chitosan Beads under Single and Mixed Conditions

Chitosan, a natural organic polymer, has shown bifunctional characteristics in the removal of cationic and anionic contaminants from water and wastewater treatment. In particular, cationic Cu(II) and anionic phosphate can simultaneously interact with chitosan owing to the presence of the amino group in the form of NH₂ and NH₃⁺ in chitosan. To gain greater insight into the bifunctional adsorption characteristics of chitosan, its adsorption capacity for Cu(II) and phosphate was tested under single and mixed (co-ion) conditions to investigate the interactions between four types of chitosan beads and NH₂ and NH₃⁺. In the single condition, Cu(II) uptake was reduced from 0.243 to 0.0197 mmol/g due to the crosslinking and drying processes, whereas no significant reduction in phosphate uptake was observed, indicating that the crosslinking agent only interacted with NH₂ to decrease the number of available adsorption sites for Cu(II). Under the mixed condition, the simultaneous presence of the two ions clearly increased the uptake of each other, with the adsorption of phosphate being more influenced than that of Cu(II). The comparison of the rate constant, k₁ or k₂, using pseudo-first- and pseudo-second-order models confirmed that phosphate reached equilibrium faster than Cu(II), suggesting that electrostatic interaction was preferred over coordination. In addition, under mixed conditions, co-ion competition slowed down the adsorption kinetics for both Cu(II) and phosphate.

Fabrication of a waste cotton fabrics-based nanosystem for simultaneous removal of Cu(II) and Pb(II)

Herein, a waste cotton fabrics-based nanosystem was fabricated to simultaneously remove copper (Cu(II)) and lead ions (Pb(II)) from water and soil. Therein, carboxyl-functionalized zinc oxide microsphere (ZnO-COOH) with peanut shape was carried by cotton fabric (CF) to get CF/ZnO-COOH nanosystem. CF/ZnO-COOH with a good foldable property possessed a high removal capacity for Cu(II) and Pb(II) via electrostatic attraction and chelation. The result indicated that their removal efficiencies of CF/ZnO-COOH could reach over 95% after 2 h. The adsorption process was consistent with Langmuir (R² = 0.9905 of Cu(II) and R² = 0.9846 of Pb(II)) and pseudo-second-order kinetic models (R² = 0.9999 of Cu(II) and R² = 0.9999 of Pb(II)). The thermodynamic data showed that the adsorption process was spontaneous and exothermic. Additionally, CF/ZnO-COOH also possessed a high fixation ability for Cu(II) and Pb(II) in sand-soil column, especially for Pb(II) (15 cm, 0.4 μg kg^-1). Therefore, this wok provides an environmentally friendly and efficient way to remove Cu(II) and Pb(II) from water and soil concurrently.

The effect of spin-lattice relaxation on DEER background decay

The common approach to background removal in double electron-electron resonance (DEER) measurements on frozen solutions with a three-dimensional homogeneous distribution of doubly labeled biomolecules is to fit the background to an exponential decay function. Excluded volume effects or distribution in a dimension lower than three, such as proteins in a membrane, can lead to a stretched exponential decay. In this work, we show that in cases of spin labels with short spin-lattice relaxation time, up to an order of magnitude longer than the DEER trace length, relevant for metal-based spin labels, spin flips that take place during the DEER evolution time affect the background decay shape. This was demonstrated using a series of temperature-dependent DEER measurements on frozen solutions of a nitroxide radical, a Gd(III) complex, Cu(II) ions, and a bis-Gd(III) model complex. As expected, the background decay was exponential for the nitroxide, whereas deviations were noted for Gd(III) and Cu(II). Based on the theoretical approach of Keller et al. (Phys. Chem. Chem. Phys. 21 (2019) 8228-8245), which addresses the effect of spin-lattice relaxation-induced spin flips during the evolution time, we show that the background decay can be fitted to an exponent including a linear and quadratic term in t, which is the position of the pump pulse. Analysis of the data in terms of the probability of spontaneous spin flips induced by spin-lattice relaxation showed that this approach worked well for the high temperature range studied for Gd(III) and Cu(II). At the low temperature range, the spin flips that occured during the DEER evolution time for Gd(III) exceeded the measured spin-lattice relaxation rate and include contributions from spin flips due to another mechanisms, most likely nuclear spin diffusion.

Multifunctional Silica-Based Amphiphilic Block Copolymer Hybrid for Cu(II) and Sodium Oleate Adsorption in Beneficiation Wastewater

Beneficiation wastewater contains various types of pollutants, such as heavy metal ions and organic pollutants. In this work, a silica-based amphiphilic block copolymer, SiO₂-g-PBMA-b-PDMAEMA, was obtained by surface-initiated atom transfer radical polymerization (SI-ATRP) for Cu(II) and sodium oleate adsorption in beneficiation wastewater, using butyl methacrylate (BMA) as a hydrophobic monomer and 2-(dimethylamino)ethylmethacrylate (DMAEMA) as a hydrophilic monomer. FTIR, TGA, NMR, GPC, XRD, N₂ adsorption-desorption isotherms and TEM were used to characterize the structure and morphology of the hybrid adsorbent. The introduction of PBMA greatly increased the adsorption of sodium oleate on SiO₂-g-PBMA-b-PDMAEMA. Adsorption kinetics showed that the adsorption of Cu(II) or sodium oleate on SiO₂-g-PBMA-b-PDMAEMA fitted the pseudo-second-order model well. Adsorption isotherms of Cu(II) on SiO₂-g-PBMA-b-PDMAEMA were better described by the Langmuir adsorption isotherm model, and sodium oleate on SiO₂-g-PBMA-b-PDMAEMA was better described by the Freundlich adsorption isotherm model. The maximum adsorption capacity of Cu(II) and sodium oleate calculated from Langmuir adsorption isotherm equation reached 448.43 mg·g^-1 and 129.03 mg·g^-1, respectively. Chelation and complexation were considered as the main driving forces of Cu(II) adsorption, and the van der Waals force as well as weak hydrogen bonds were considered the main driving forces of sodium oleate adsorption. The adsorbent was recyclable and showed excellent multicomponent adsorption for Cu(II) and sodium oleate in the mixed solution. SiO₂-g-PBMA-b-PDMAEMA represents a satisfying adsorption material for the removal of heavy metal ions and organic pollutants in beneficiation wastewater.

Changes in metal adsorption ability of microplastics upon loss of calcium carbonate filler masterbatch through natural aging

CaCO₃ filler masterbatch (CFM) is one of the most commonly used fillers in polypropylene (PP) and polyethylene (PE) products, and its is used to enhance the toughness of the polymer matrix. This is the first study to investigate the loss of CaCO₃ and its impact on the adsorption ability of microplastics from plastic woven bags throughout the natural aging process. PP wire (PPw, 85% PP + 15% CFM) and PE film (PEf, 80% PE + 20% CFM) samples from plastic woven bags underwent a 250 d aging process in an open-air environment. Changes in the surface properties, morphology, CaCO₃ content, and density of PPw microplastics (PPw-MP) and PEf microplastics (PEf-MP) after various durations of aging were investigated by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. The results showed that CaCO₃ separated and agglomerated on the surfaces of PPw-MP and PEf-MP after 30 d. After 250 d, 42% of CaCO₃ was lost from PPw-MP and 28% was lost from PEf-MP, decreasing the density of the microplastic samples. CFM presented a considerably higher adsorption affinity toward Cu(II) than PP particles and PE particles; therefore, its presence in plastic matrix increased the adsorption ability of the products. The adsorption of Cu(II) on PPw-MP and PEf-MP decreased with aging because of the loss of CaCO₃ and poor development of O-containing functional groups. The q_m value (maximum adsorption quantity of Langmuir model) decreased from 11.01 mg/g in unaged PPw-MP to 1.35 mg/g in aged PPw-MP, and from 9.00 mg/g in unaged PEf-MP to 1.05 mg/g in aged PEf-MP. Overall, the findings demonstrate that CaCO₃ was crucial for the heavy metal-plastic interactions of the samples. Therefore, the results provide a basis to further clarify the potential environmental risks of plastic woven bags associated with heavy metal mobility.

APTMS-BCAD modified magnetic iron oxide for magnetic solid-phase extraction of Cu(II) from aqueous solutions

Fe₃O₄@SiO₂-3-aminopropyltrimethoxysilane-1,8-bis (3-chloropropoxy) anthracene-9,10-dione was synthesized as a new, sustainable, and environmentally friendly adsorbent for magnetic solid-phase extraction of Cu(II) from aqueous solutions. The structure of the adsorbent was characterized by FTIR, XRD, SEM, EDX, and TEM analysis. Optimum conditions for Cu(II) adsorption were determined as adsorbent dose 0.04 g, pH 5.0, contact time 120 min, and beginning concentration of 30 mg/L in the adsorption process. The adsorption capacity for Cu(II) ions was 43.67 mg/g and the removal efficiency was 84.72 percent. The Langmuir isotherm and the pseudo-second-order model fit the experimental data better. Adsorption was a spontaneous and endothermic process based on the obtained thermodynamic properties such as ΔG°, ΔH°, and ΔS°. The results showed that the sorbent has good selectivity in the presence of competing ions. The method was determined to be accurate and effective using real water samples and CRM.

•

Magnetic Fe₃O₄@SiO₂-3-aminopropyl-trimethoxysilane-1,8-bis(3-chloropro-poxy) anthracene-9,10-dione was synthesized as a new, sustainable, and environmentally friendly adsorbent for magnetic solid-phase extraction of Cu(II) from aqueous solutions.

•

The results showed that the presence of competitor ions did not have a significant effect on the sorption of Cu(II) ion and the sorbent had good selectivity.

•

Using real water samples and CRM, the method was found to be accurate and effective.

Pyrolysis of grape bagasse to produce char for Cu(II) adsorption: a circular economy perspective

Based on cleaner production and circular economy concepts, chars were produced through thermochemical conversion of grape bagasse and then used as adsorbents to uptake Cu(II) from aqueous media since Cu(II) is a common element found in fungicides to treat grapevines. The grape bagasse and char characteristics were investigated through several analytical techniques (TGA, SEM, XRD, FTIR, and BET). Three chars were obtained using different pyrolysis temperatures: 700, 800, and 900 °C. The materials had similar removal percentages and adsorption capacity. The char produced at 700 °C was chosen due to its lower production cost. Studies were conducted on the adsorbent dosage and pH effect, adsorption kinetics, isotherms, and thermodynamics. The most efficient dosage was 1.5 g L-1, and the pH was 5.5. The kinetic study showed that the equilibrium was reached in 60 min and the pseudo-second-order model presents the best fit. After the temperature influence study (25, 35, 45, and 55 °C), it was possible to verify that Cu(II) adsorption through char was favored at 55 °C. The Freundlich model showed the best fit for the experimental data. The highest removal percentage was 96.56%, and the high maximum adsorption capacity was 42 mg g-1. The thermodynamic study shows the adsorption as a spontaneous process, favorable, and endothermic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13399-022-02792-8.

A resonance Rayleigh scattering method for sensitive detection of chitosan based on supramolecular complex and mechanism study

A convenient and sensitive resonance Rayleigh scattering (RRS) method for the detection of chitosan (CTS) has been developed via forming Cu-Zn supramolecular complex by complexation reaction, hydrophobic force and electrostatic attraction. The microstructure of the complex was characterized by FT-IR, zeta potential, scanning electron microscope (SEM), UV-vis and RRS. Furthermore, the interaction mechanism among Cu(II), Zn(II), CTS and sodium dodecyl benzene sulfonate (SDBS) was studied. The results revealed that CTS and Cu(II) or Zn(II) formed a supramolecular complex with RRS enhancement in weak acid condition. In the presence of SDBS, the RRS intensity of CTS-Cu(II)-SDBS or CTS-Zn(II)-SDBS was significantly higher than that of the binary system without SDBS at the same CTS concentration. The RRS intensity of CTS-Cu(II)-Zn(II)-SDBS was higher than that of CTS-Cu(II)-SDBS and CTS-Zn(II)-SDBS. The RRS intensity increased linearly with the increase of CTS concentration made it possible to determine CTS quantitatively. In the range extending from 0.10 to 5.00 μg/mL, the equation of linear regression was ΔI=1848.8c-138.3 with a correlation coefficient 0.9996, and the detection limit was estimated to be 37.96 ng/mL. The study was successfully applied for the determination of CTS in health food samples, suggesting its great potential toward CTS analysis.

The fast redox cycle of Cu(II)-Cu(I)-Cu(II) in the reduction of Cr(VI) by the Cu(II)-thiosulfate system

Thiosulfate (S₂O₃^2-) is an important ligand to complex metal cations, however, the reactivity of metal-thiosulfate complexes has barely been mentioned. In this study, the reactivity of the Cu(II)-S₂O₃^2- system in the reduction of Cr(VI) was investigated. Kinetic results show that the reduction rates of Cr(VI) decrease with increasing pH values from 3.0 to 5.0, and 94.3% and 97.5% of 10 mg L^-1 Cr(VI) was rapidly reduced within 1 min at pH 3.0 and within 30 min at pH 5.0, respectively at the molar ratio of Cu(II):S₂O₃^2- of 0.05. We rule out the contributions of S species of tetrathionate (S₄O₆^2-) and sulfite (SO₃^2-) to Cr(VI) reduction and point out that the produced Cu(I) in the Cu(II)-S₂O₃^2- system is the key reductant that mediates the reduction of Cr(VI). We suggest that complexation between Cu(II) and S₂O₃^2- with the formation of Cu^II(S₂O₃)₂^2- is the pre-requisite for the formation of Cu^I(S₂O₃)_n^1-2n, which plays an important role in Cr(VI) reduction, accompanied by the re-oxidation of Cu(I) to Cu(II) by Cr(VI), achieving the rapid redox cycling of Cu(II)-Cu(I)-Cu(II). Such a redox cycle also mediates the denitrification process of NO₂^- to NH₃/NH₄⁺ under weakly acidic conditions. This study enriches our understanding on the reducing reactivity of the Cu(II)-S₂O₃^2- system and the importance of the Cu(II)-Cu(I)-Cu(II) redox cycle towards environmental oxidizing contaminants.

Mechanistic insights into enhanced waste activated sludge dewaterability with Cu(II) and Cu(II)/H2O2 treatment: Radical and non-radical pathway

Without extra adjustment of pH, the effects of cupric ions (Cu(II)) and hydrogen peroxide (H₂O₂) alone or in combination on sludge dewatering were studied. It showed good dewatering capability after treated by Cu(II) and Cu(II)/H₂O₂, which indicated by the capillary suction times (CST) decreased from 120.8 ± 4.7 s (control) to about 40 s, and the water content (Wc) of sludge cake dropped by about 10%. The results showed that the extracellular polymeric substances (EPS) were destroyed, which characterized by a significant decrease in the biopolymers' concentrations in tightly-bound EPS. Meanwhile, more rough and porous microstructures and higher zeta potentials were obtained after conditioned. Based on the changes of physicochemical properties of sludge, the variations of EPS, and the identification of reactive species, two distinct mechanisms of improved sludge dewatering were postulated. As for Cu(II) treatment, it was mainly due to the surface charge neutralization, strong cytotoxicity of Cu(I) produced by intracellular reduction of Cu(II), and pH decline caused by Cu(II) hydrolysis that improved sludge dewatering performance, which could be noted as a "non-radical pathway". When in combination with H₂O₂, hydroxyl radicals (·OH) produced by Cu(II)-catalyzed Fenton-like process played a dominant role in degrading sludge flocs and EPS, which could be regarded as a "radical pathway".

Effect of biochar-derived DOM on the interaction between Cu(II) and biochar prepared at different pyrolysis temperatures

The structure and composition of biochar-derived dissolved organic matter (DOM) at different pyrolysis temperatures differed significantly, affecting the environmental geochemical behavior of heavy metals (HMs). Herein, the binding properties of Cu(II) onto walnut-shell DOM were investigated using spectroscopic methods. The results showed that the DOM at low pyrolysis temperatures (300 °C and 500 °C) showed higher Cu(II) affinity than that at high pyrolysis temperature (700 °C). There was a preferential Cu(II) binding with fulvic-like substances (360 nm) at 300 °C, and with protein-like materials (275 nm) at 500 °C and 700 °C. The C-O group of alcohols, ethers, and esters showed preferential binding with Cu(II) at 300 °C and 700 °C pyrolysis temperatures. However, preferential bonding of Cu(II) to the C-O stretching vibration and O-H bending vibration of carboxyl was exhibited at 500 °C pyrolysis temperature. Pyrolysis temperature played a crucial role in the release of biochar-derived DOM and in the migration and bioavailability of HMs. Meanwhile, the adsorption effect of Cu(II) increased by 11.2% for biochar at 300 °C, and decreased by 15.0% and 61.1% for biochar at 500 °C and 700 °C, respectively, after the removal of DOM, suggesting that the presence of DOM influenced the adsorption behavior of biochar towards Cu(II).

Cu(II) assisted peroxymonosulfate oxidation of sulfonamide antibiotics: The involvement of Cu(III)

Cu(II) is generally considered to be a poor activator for PMS decomposition, thus the potential impact of trace Cu(II) on PMS induced oxidation of typical pollutants is always overlooked. In this study, we reported that trace Cu(II) could significantly promote PMS induced degradation of four selected sulfonamide antibiotics (SAs), namely, sulfamehoxazole (SMX), sulfathiazole (STZ), sulfamerazine (SMZ), and sulfamonomethoxine (SMM). Different from conventional PMS-induced oxidation process, high-valent Cu(III) was ascertained as the primary reactive intermediate for SAs degradation, which was confirmed by raman tests and electron paramagnetic resonance (EPR). High concentrations of Cu(II) or PMS were beneficial to degradation of the selected contaminants. In PMS/Cu(II) oxidation system, all the selected SAs could undergo several different degradation pathways including continuous oxidation of aniline group, hydroxylation and S-N bond cleavage. In particular, for six-membered SAs, such as SMZ and SMM, a SO₂ extrusion pathway was also detected. The potential mechanism for Cu(III) formation was also proposed, which was believed to be highly related to the nature of the SAs. Hydroxylamine-SAs (N⁴-OH-SAs), generated from direct PMS oxidation of SAs, was deduced as the "promoter" for the whole oxidation process. And the generation of Cu(III) was likely to proceed through the interaction between PMS and Cu(I), which possibly derived from the reduction of Cu(II) by N⁴-OH-SAs. The results obtained in this study validated the contribution of Cu(III) to the elimination of pollutants and expanded our understanding of the oxidation process of PMS in the presence of trace amounts of Cu(II).

A simple strategy for the detection of Pb(II) and Cu(II) by an electrochemical sensor based on Zn/Ni-ZIF-8/XC-72/Nafion hybrid materials

In this study, a novel electrochemical sensor for simultaneous detection of Pb(II) and Cu(II) was constructed by using Zn/Ni-ZIF-8/XC-72/Nafion hybrid material as electrode surface modifier. XRD, FT-IR, XPS and SEM were used to study the crystal structure, functional groups, element types and morphologies of the prepared materials. The electrochemical performance of the Zn/Ni-ZIF-8/XC-72/Nafion/GCE sensor were investigated by CV, EIS and DPV. In addition, the effects of various conditions including pH, the type of buffer and the ratio of Zn/Ni-ZIF-8 to XC-72 were also explored for the determination of Pb(II) and Cu(II). Under the optimum conditions, the constructed sensor exhibited outstanding linear response of Pb(II) (0.794-39.6 ppm) and Cu(II) (0.397-19.9 ppm) with detection limits of 0.0150 and 0.0096 ppm, respectively. Finally, the fabricated sensor was further used to detect Pb(II) and Cu(II) in real samples, and the satisfactory recovery was obtained.

Synthesis of Calcium Silicate Hydrate from Coal Gangue for Cr(VI) and Cu(II) Removal from Aqueous Solution

Both the accumulation of coal gangue and potentially toxic elements in aqueous solution have caused biological damage to the surrounding ecosystem of the Huainan coal mining field. In this study, coal gangue was used to synthesize calcium silicate hydrate (C-S-H) to remove Cr(VI) and Cu(II)from aqueous solutions and aqueous solution. The optimum parameters for C-S-H synthesis were 700 °C for 1 h and a Ca/Si molar ratio of 1.0. Quantitative sorption analysis was done at variable temperature, C-S-H dosages, solution pH, initial concentrations of metals, and reaction time. The solution pH was precisely controlled by a pH meter. The adsorption temperature was controlled by a thermostatic gas bath oscillator. The error of solution temperature was controlled at ± 0.3, compared with the adsorption temperature. For Cr(VI) and Cu(II), the optimum initial concentration, temperature, and reaction time were 200 mg/L, 40 °C and 90 min, pH 2 and 0.1 g C-S-H for Cr(VI), pH 6 and 0.07 g C-S-H for Cu(II), respectively. The maximum adsorption capacities of Cr(VI) and Cu(II) were 68.03 and 70.42 mg·g⁻¹, respectively. Furthermore, the concentrations of Cu(II) and Cr(VI) in aqueous solution could meet the surface water quality standards in China. The adsorption mechanism of Cu(II) and Cr(VI) onto C-S-H were reduction, electrostatic interaction, chelation interaction, and surface complexation. It was found that C-S-H is an environmentally friendly adsorbent for effective removal of metals from aqueous solution through different mechanisms.

Free-electrodeposited anodic stripping voltammetry sensing of Cu(II) based on Ti3C2Tx MXene/carbon black

A proof-of-principle concept for free-electrodeposited anodic stripping voltammetry (ASV) sensing of Cu²⁺ is proposed by using Ti₃C₂T_x MXene/carbon black (Ti₃C₂T_x@CB) nanohybrids as electrode materials. Owing to the high adsorption and reduction capability of Ti₃C₂T_x towards Cu²⁺, Ti₃C₂T_x MXene enables Cu²⁺ to be immobilized and self-reduced directly to form Cu⁰ on the Ti₃C₂T_x@CB electrode surface. As a result an oxidation peak current appears from the re-oxidation of Cu⁰ via differential pulse voltammetry. Carbon black (CB) was introduced to prevent Ti₃C₂T_x Mxene aggregation and improve the related electron transfer as well as enhance their surface area. After optimizing various conditions, a considerable low limit of detection (4.6 nM) and a wide linear range (0.01-15.0 μM) for Cu²⁺ were achieved at the working potential from - 0.3 V to 0.0 V (vs SCE). Relative standard deviation (RSD) of eight individual Ti₃C₂T_x@CB electrodes is 3.72%, and the recoveries from tap water sample and lake water sample were in the ranges of 97.0-108% and 104-107%, respectively.

Bi-layered hollow amphoteric composites: Rational construction and ultra-efficient sorption performance for anionic Cr(VI) and cationic Cu(II) ions

Here, we have developed a novel bilayer hollow amphiphilic biosorbent (BHAB-3) with large adsorption capacity, rapid adsorption kinetics, and cost-effective for the removal of Cr(VI) and Cu(II) from aqueous solutions. The synthesis was based on the clever use of freeze-drying to fix the structure, secondary modification of the carboxymethyl cellulose microspheres with polyethyleneimine and cross-linking by glutaraldehyde. The consequences of pH, initial concentration, contact time and temperature on adsorption were investigated. The Langmuir model fits showed that the maximum adsorption capacities of the two target heavy metal ions reached 835.91 and 294.79 mg/g, respectively. Moreover, BHAB-3 was characterized by SEM, FT-IR, TGA, and XPS synergistically, showing that it exhibits a strong complexation ability for Cu(II) and a strong electrostatic effect for Cr(VI). Adsorption and desorption experiments showed only a slight decrease in the adsorption capacity of the BHAB-3 for Cr(VI) and Cu(II) ions after 5 and 26 cycles, respectively. Given the excellent properties of this adsorbent, it is a promising candidate for heavy metal ion removal.

Hydrolytic cleavage of nerve agent simulants by gold nanozymes

Although banned by the Chemical Weapons Convention, organophosphorus nerve agents are still available and have been used in regional wars, terroristic attacks or for other crtaiminal purposes. Their degradation is of primary importance for the severe toxicity of these compounds. Here we report that gold nanoparticles passivated with thiolated molecules bearing 1,3,7-triazacyclononane and 1,3,7,10-tetraazacyclododecane ligands efficiently hydrolyze nerve agents simulants p-nitrophenyl diphenyl phosphate and methylparaoxon as transition metal complexes at 25 °C and pH 8 with half-lives of the order of a few minutes. Mechanistically, these catalysts show an enzyme-like behavior, hence they constitute an example of nanozymes. The catalytic site appears to involve a single metal ion and its recognition of the substrates is driven mostly by hydrophobic interactions. The ease of preparation and the mild conditions at which they operate, make these nanozymes appealing catalysts for the detoxification after contamination with organophosphorus nerve agents, particularly those poorly soluble in water.

Insights into the adsorption mechanism of tannic acid by a green synthesized nano-hydroxyapatite and its effect on aqueous Cu(II) removal

The polyphenolic tannic acid (TA) has been widely used in the stabilization and surface modification of nanomaterials. The interaction mechanism of TA with the biogenic nano-hydroxyapatite (nHAP) and its environmental importance, however, are poorly understood. This study explored the adsorption of TA using the green synthesized, eggshell-derived nHAP and implications of this process for the removal of aqueous Cu(II) via batch adsorption experiments, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) investigations. TA adsorption by nHAP was a complex pH-dependent process and significantly correlated with TA molecule speciation and amphoteric properties of nHAP via multiple adsorption modes including surface complexation, electrostatic attraction, and hydrogen bond. The maximum TA adsorption amount was found to be 94.8 mg/g for less crystalline nHAP with lower calcination temperature. In the ternary Cu-TA-nHAP systems, TA promoted Cu(II) adsorption at pH < 5 and reduced Cu(II) uptake at pH > 5. Further studies of the effects of ionic strength and addition sequences, as well as Raman, FTIR, and XPS analyses revealed Cu(II) adsorption on nHAP was mainly dominated by inner-sphere surface complexation. These results can shed light on not only the utility of biogenic nHAP for TA and Cu(II) adsorption but also the evaluation of the effect of TA on the environmental behavior of heavy metals.

A Novel Cu(II)-Binding Peptide Identified by Phage Display Inhibits Cu2+-Mediated Aβ Aggregation

Copper (Cu) has been implicated in the progression of Alzheimer’s disease (AD), and aggregation of Cu and amyloid β peptide (Aβ) are considered key pathological features of AD. Metal chelators are considered to be potential therapeutic agents for AD because of their capacity to reduce metal ion-induced Aβ aggregation through the regulation of metal ion distribution. Here, we used phage display technology to screen, synthesize, and evaluate a novel Cu(II)-binding peptide that specifically blocked Cu-triggered Aβ aggregation. The Cu(II)-binding peptide (S-A-Q-I-A-P-H, PCu) identified from the phage display heptapeptide library was used to explore the mechanism of PCu inhibition of Cu²⁺-mediated Aβ aggregation and Aβ production. In vitro experiments revealed that PCu directly inhibited Cu²⁺-mediated Aβ aggregation and regulated copper levels to reduce biological toxicity. Furthermore, PCu reduced the production of Aβ by inhibiting Cu²⁺-induced BACE1 expression and improving Cu(II)-mediated cell oxidative damage. Cell culture experiments further demonstrated that PCu had relatively low toxicity. This Cu(II)-binding peptide that we have identified using phage display technology provides a potential therapeutic approach to prevent or treat AD.

Cu(II) complex with auxin (3-indoleacetic acid) and an aromatic planar ligand: synthesis, crystal structure, biomolecular interactions and radical scavenging activity

A novel water soluble ternary copper(II) complex,-[Cu₂(phen)₂(3-IAA)₂(H₂O)](ClO₄)₂·H₂O-(phen: 1,10-phenanthroline, 3-IAA: 3-indoleacetic acid), has been synthesized and characterized by elemental CHN analysis, ESI-TOF, FTIR and single-crystal X-ray diffraction techniques. Interaction of the complex with calf thymus DNA (CT-DNA) has been investigated by absorption spectral titration, ethidium bromide (EB) and Hoechst 33258 displacement assay. The interactions between the complex and bovine serum albumin (BSA) were investigated by electronic absorption and fluorescence spectroscopy methods. The experimental results indicate that the fluorescence quenching mechanism between the complex and BSA is a static quenching process. The Stern-Volmer constants, binding constants, binding sites and the corresponding thermodynamic parameters (ΔG, ΔH, ΔS) of BSA + complex systems were determined at different temperatures. The binding distance between the complex and BSA was calculated according to Förster non-radiation energy transfer theory (FRET). The effect of the complex on the conformation of BSA was also examined using synchronous, two dimensional (2D) and three dimensional (3D) fluorescence spectroscopy. Furthermore, the oxygen radical scavenging activity of the complex was determined in terms of IC₅₀, using the DPPH and H₂O₂ method, to show that it particularly enables electron loss from radical species. This study highlights the importance of indole and moieties in the development of antioxidant agents. A potent drug candidate novel water soluble ternary copper(II) complex,-[Cu₂(phen)₂(3-IAA)₂(H₂O)] (ClO₄)₂·H₂O-(phen: 1,10-phenanthroline, 3-IAA: 3-indoleacetic acid), has been synthesized and characterized by elemental CHN analysis, FTIR, ESI-MS and single-crystal X-ray diffraction techniques. The complex has been tested for in vitro biomacromolecular interactions by spectroscopic methods. Furthermore, radical scavenging activities of the complex were also investigated.

Effects of hydrophyte decomposition on the binding mechanism between fluorescent DOM and copper

Hydrophyte decomposition caused large amounts of dissolved organic matter (DOM) to enter aquatic environment that influence the migration and transformation of heavy metals (HMs). Six hydrophytes with five dry weight gradients (DWG) were used for the decomposition experiments. The results showed that protein-like materials occupy relatively high content in the hydrophyte-derived DOM. The binding properties of DOM-Cu(II) have been explored by using two-dimensional correlation spectroscopy (2D-COS) in conjunction with synchronous fluorescence spectroscopy (SFS) and log-transformed SFS. The weak signals of binding site can be amplified by the log-transformed 2D-COS analysis. Herein, more binding sites can be identified by the log-transformed 2D-COS analysis. The results reveal that tryptophan-like materials show a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively low DWG and sediment DOM, and fulvic-like substances indicate a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively high DWG. Meanwhile, the results of binding parameters indicate that the log K is the range of 3.61-4.25, 4.33-4.74, 4.59-4.97, 3.91-4.41, and 4.14-4.78 for D1-D5, respectively, suggesting that hydrophyte decomposition can change the binding affinity between DOM components and Cu(II). The complexes of fluorescent components with Cu(II) showed a high log K value at long wavelength (e.g. humic-like substances), and a relatively low fluorescent ligand proportion (f%) at shorter wavelength in the hydrophyte-derived DOM. However, the log K is the range of 3.08-4.31, 4.09-4.45, 3.93-4.35, 4.39-4.75, and 3.95-4.36 for C1-C5, separately. Protein-like substances with Cu(II) showed a relatively high log K value with the exception of C4. The log-transformed 2D-COS can be an analytical tool to understand the binding heterogeneity of DOM with HMs. The study can provide a guide for managing and controlling the effects of hydrophyte decomposition.

Characterization of biochars derived from various spent mushroom substrates and evaluation of their adsorption performance of Cu(II) ions from aqueous solution

A total of 16 biochar adsorbents were produced from four types of spent mushroom substrates to investigate the effect of pyrolysis temperature and raw material composition on the Cu(II) adsorption performance of the resulting biochars. It was determined that the pyrolysis temperature and substrate composition markedly influenced the thermal stability, the degree of carbonization, surface functional group content, and structural morphology of the biochars, but did not affect the adsorption isotherms or kinetics. Optimal results were obtained with an initial pH of 5, adsorbent dosage of 1 g/L, Cu(II) concentration of 50 mg/L, and temperature of 25 °C. The four best-performing biochars conformed to the Langmuir isotherm model and followed pseudo-second-order kinetics with maximum Cu(II) adsorption between 52.6 and 65.6 mg/g. Precipitation was the dominant mechanism for Cu(II) adsorption onto Lentinus edodes spent substrate-derived biochar pyrolyzed at 600 °C (LESS600), whereas complexation with surface functional groups was the prominent mechanism of Cu(II) removal by Auricularia auricula spent substrate-derived biochar pyrolyzed at 500 °C (AASS500). The Flammulina velutipes and Pleurotus ostreatus spent substrate-derived biochars pyrolyzed at 600 °C (FVSS600 and POSS600, respectively) removed Cu(II) ions using both precipitation and Cu²⁺-π complexation interactions. The findings indicate that biochar derived from spent mushroom substrates containing abundant lignin and pyrolyzed at high temperatures (500 or 600 °C) demonstrate effective Cu(II) removal because of the various physico-chemical properties discussed herein.

Adsorption behaviors of the pristine and aged thermoplastic polyurethane microplastics in Cu(II)-OTC coexisting system

In this work, the hypothesis that thermoplastic polyurethane (TPU) microplastics (MPs) could form complex toxic pollution by absorbing both antibiotics and heavy metals simultaneously was proposed. The unique features of the adsorption of Cu(II) and oxytetracycline (OTC) on the pristine TPU and photo-aged (aged) TPU MPs in single and coexisting system were investigated, which included the kinetics, isothermal equilibrium and thermodynamics. The possibly synergistic or competitive effects between Cu(II) and OTC were also evaluated. The results showed that the adsorption process of Cu(II) and OTC could be described well by pseudo-second-order kinetic equation. The entire process could be divided into two stages: internal diffusion and external diffusion. The Sips model could give good fitting for the isothermal adsorption equilibrium. The thermodynamic parameters depicted the endothermic nature of adsorptions and the process was spontaneous. In the coexisting system, synergistic or competitive effects depended critically on the ratio of concentrations (Cu(II) vs OTC). When the ratio was 1:1, Cu(II) significantly enhanced the adsorption of OTC, while OTC showed a weak effect on Cu(II) adsorption. The synergies could be attributed to the formation of Cu(II)-OTC complex and the bridging effect of Cu(II). Overall, the adsorption capacity of aged TPU was higher than that of pristine TPU, which was due to the differences in morphological characteristics and functional groups. FTIR studies revealed that ester carbonyl and acylamino groups in the TPU may be involved in the adsorption of Cu(II) and OTC.

Interfacial interactions between collected nylon microplastics and three divalent metal ions (Cu(II), Ni(II), Zn(II)) in aqueous solutions

In water environments, nylon microplastics (MPs) and heavy metals are two kinds of common pollutants. This study investigated the adsorption of three divalent metals (Cu(II), Ni(II), Zn(II)) onto collected nylon MPs as function of contact time, temperature, solution pH, ionic strength and concentration of fulvic acid (FA). The kinetic data fitted well with the Elovich and pseudo-second order equations. The result of shrinking core model (SCM) confirms that the adsorption of Cu(II) and Zn(II) was mainly controlled by intraparticle diffusion. The adsorption of three metal ions onto collected nylon MPs is spontaneous, endothermic, with an increased randomness in nature. The Langmuir and Freundlich models successfully described the adsorption isotherms. The speciation distributions of three divalent metals in aqueous solutions were identified to analyze the effects of initial solution pH, ionic strength and fulvic acid concentrations on the adsorption amounts. X-ray photoelectron spectroscopy (XPS) analysis indicates the importance of surface O-containing groups of collected nylon MPs in controlling the adsorption of three metal ions. This research provides a clear theoretical basis for the behavior of nylon MPs as heavy metals (Cu(II), Ni(II), Zn(II)) carrier and highlights their environmental toxicity, which deserves to be further concerned.

Enhanced adsorption/photocatalytic removal of Cu(Ⅱ) from wastewater by a novel magnetic chitosan@ bismuth tungstate coated by silver (MCTS-Ag/Bi2WO6) composite

An easily separation composite, magnetic chitosan@bismuth tungstate coated by silver (MCTS-Ag/Bi₂WO₆), was successfully synthesized by the simple hydrothermal method. Moreover, the MCTS-Ag/Bi₂WO₆ demonstrated excellent adsorption/photocatalytic removal of Cu(II) in aqueous solution. Adsorption played a leading role in the synergistic reaction. The catalysts were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The effects on adsorption of Cu(II) were investigated, which included illumination, pH, and initial concentration. The experimental results showed that the theoretical maximum adsorption capacity of Cu(II) (181.8 mg/g) was achieved under simulated solar light irradiation with the optimal pH value of 6.0, indicating that illumination could enhance the adsorption of Cu(II) by MCTS-Ag/Bi₂WO₆. Meanwhile, the composite exhibited desirable adsorption ability of Cu(II) after 5 cycles. The copper ion adsorption fitted well with pseudo-second-order kinetic model and its isotherm followed Freundlich model.