Oxidation of disinfectants with Cl-substituted structure by a Fenton-like system Cu(2+)/H2O2 and analysis on their structure-reactivity relationship

Laser Ablation for the Synthesis of Cu/Cu2O/CuO and Its Development as Photocatalytic Material for Escherichia coli Detoxification

Advanced Oxidation Processes (AOPs) offer promising methods for disinfection by generating radical species like hydroxyl radicals, superoxide anion radicals, and hydroxy peroxyl, which can induce oxidative stress and deactivate bacterial cells. Photocatalysis, a subset of AOPs, activates a semiconductor using specific electromagnetic wavelengths. A novel material, Cu/Cu2O/CuO nanoparticles (NPs), was synthesized via a laser ablation protocol (using a 1064 nm wavelength laser with water as a solvent, with energy ranges of 25, 50, and 80 mJ for 10 min). The target was sintered from 100 °C to 800 °C at rates of 1.6, 1.1, and 1 °C/min. The composite phases of Cu, CuO, and Cu2O showed enhanced photocatalytic activity under visible-light excitation at 368 nm. The size of Cu/Cu2O/CuO NPs facilitates penetration into microorganisms, thereby improving the disinfection effect. This study contributes to synthesizing mixed copper oxides and exploring their activation as photocatalysts for cleaner surfaces. The electronic and electrochemical properties have potential applications in other fields, such as capacitor materials. The laser ablation method allowed for modification of the band gap absorption and enhancement of the catalytic properties in Cu/Cu2O/CuO NPs compared to precursors. The disinfection of E. coli with Cu/Cu2O/CuO systems serves as a case study demonstrating the methodology's versatility for various applications, including disinfection against different microorganisms, both Gram-positive and Gram-negative.

A review of copper-based Fenton reactions for the removal of organic pollutants from wastewater over the last decade: different reaction systems

In recent years, as global industrialization has intensified, environmental pollution has become an increasingly serious problem. Improving water quality and achieving wastewater purification remain top priorities for environmental health initiatives. The Fenton process is favored by researchers due to its high efficiency and ease of operation. Central to the Fenton process is a catalyst used to activate hydrogen peroxide, rapidly degrading pollutants, improving water quality. Among various catalysts developed, copper-based catalysts have attracted considerable attention due to their affordability, high activity, and stable performance. Based on this, this paper reviews the development of copper-based Fenton systems over the past decade. It mainly involves the research and application of copper-based catalysts in different Fenton systems, including photo-Fenton, electro-Fenton, microwave-Fenton, and ultrasonic-Fenton. This review provides a fundamental reference for the subsequent studies of copper-based Fenton systems, contributing to the goal of transitioning these systems from laboratory research into practical environmental applications.

Copper Nanodots-Based Hybrid Hydrogels with Multiple Enzyme Activities for Acute and Infected Wound Repair

Effectively controlling bacterial infection, reducing the inflammation and promoting vascular regeneration are all essential strategies for wound repair. Nanozyme technology has potential applications in the treatment of infections because its non-antibiotic dependent, topical and noninvasive nature. In wound management, copper-based nanozymes have emerged as viable alternatives to antibiotics. In this study, an ultrasmall cupric enzyme with high enzymatic activity is synthesized and added to a nontoxic, self-healing, injectable cationic guar gum (CG) hydrogel network. The nanozyme exhibits remarkable antioxidant properties under neutral conditions, effectively scavenging reactive nitrogen and oxygen species (RNOS). Under acidic conditions, Cu NDs have peroxide (POD) enzyme-like activity, which allows them to eliminate hydrogen peroxides and produce free radicals locally. Antibacterial experiments show that they can kill bacteria and remove biofilms. It reveals that low concentrations of Cu ND/CG decrease the expression of the inflammatory factors in cells and tissues, effectively controlling inflammatory responses. Cu ND/CG hydrogels also inhibit HIF-1α and promote VEGF expression in the wound with the ability to promote vascular regeneration. In vivo safety assessments reveal a favorable biosafety profile. Cu ND/CG hydrogels offer a promising solution for treating acute and infected wounds, highlighting the potential of innovative nanomaterials in wound healing.

Electrooxidation of chlorophene and dichlorophen by reactive electrochemical membrane: Key determining factors of removal efficiency

This study systematically investigated the variable main electrooxidation mechanism of chlorophene (CP) and dichlorophen (DCP) with the change of reaction conditions at Ti4O7 anode operated in batch and reactive electrochemical membrane (REM) modes. Significant degradation of CP and DCP was observed, that is, CP exhibited greater removal efficiency in batch mode at 0.5-3.5 mA cm-2 and REM operation (0.5 mA cm-2) with a permeate flow rate of 0.85 cm min-1 under the same reaction conditions, while DCP exhibited a faster degradation rate with the increase of current density in REM operation. Density functional theory (DFT) simulation and electrochemical performance tests indicated that the electrooxidation efficiency of CP and DCP in batch mode was primarily affected by the mass transfer rates. And the removal efficiency when anodic potentials were less than 1.7 V vs SHE in REM operation was determined by the activation energy for direct electron transfer (DET) reaction, however, the adsorption function of CP and DCP on the Ti4O7 anode became a dominant factor in determining the degradation efficiency with the further increase of anodic potential due to the disappeared activation barrier. In addition, the degradation pathways of CP and DCP were proposed according to intermediate products identification and frontier electron densities (FEDs) calculation, the acute toxicity of CP and DCP were also effectively decreased during both batch and REM operations.

Chlorophenols in textile dyeing sludge: Pollution characteristics and environmental risk control

Chlorophenols (CPs) are toxic contaminants that tend to accumulate in textile dyeing sludge and pose a threat to the environment through the disposal process. To comprehensively evaluate CPs in sludge, the characteristics and risks of CPs from five textile dyeing plants (TDPs) were investigated in this study. The total concentration of 19 CPs (Σ₁₉ CPs) varied from 170.90 to 6290.30 ng g^-1 dry weight (dw), among which high-chlorine phenols accounted for the greatest proportion. The ecological screening level (ESL) of CPs was used to judge their pollution levels, while the risk quotient (RQ) value and dioxin conversion rate were used to analyze their potential risk. The results indicated that CPs may pose a moderate to high risk to the environment. The Fenton process was used to condition the hazardous sludge, and a higher content of CPs was found after conditioning. A lower rate of CP increase was achieved with a reagent dose of 180 mmol/L, H₂O₂:Fe²⁺ = 1:1, pH of 3-4 and reaction time of 30 min. In summary, the work helps to address the general knowledge gap in the textile dyeing industry and provides a reference for further research.

Photo Augmented Copper-based Fenton Disinfection under Visible LED Light and Natural Sunlight Irradiation

Copper-based Fenton disinfection system (Cu(II)/H₂O₂) is an emerging advanced oxidation process (AOP). Previous works have used reducing agents and organic ligands to improve the disinfection efficiency of Cu(II)/H₂O₂ system. Here, we report visible light/Cu(II)/H₂O₂ system showed enhanced disinfection compared to Cu(II)/H₂O₂ system, without the need of reducing chemical agent or organic ligand. Energy-efficient LED array was used as a visible light source in the visible light/Cu(II)/H₂O₂ system. Under the optimized condition, pseudo-first-order inactivation rate constant (k_obs) of E. coli by visible light/Cu(II)/H₂O₂ (0.613 ± 0.005 min^-1) was about ~8 times greater than Cu(II)/H₂O₂ (0.08 ± 0.011 min^-1). Scanning electron microscopy and Baclight Live/Dead assay proved enhanced cell membrane damage by visible light/Cu (II)/H₂O₂ in comparison with Cu(II)/H₂O₂. Based on the bovine serum albumin (BSA) degradation and OH˙ radical measurement by visible light/Cu(II)/H₂O₂, a ligand to metal charge transfer (LMCT) mechanism by Cu(II)-bacterial complex is proposed for enhanced disinfection. Electrical energy efficiency (E _E,1) for a log reduction of E. coli and the total treatment cost of visible light/Cu(II)/H₂O₂ was determined to be 32.64 KWh/m³ and 350 ₹/m³ (3.9 €/m³ or 4.74 $/m³), respectively, indicating its cost-effectiveness. Disinfection efficiency by sunlight/Cu(II)/H₂O₂ system (solar irradiance; 746 ± 138 W/m²) was almost comparable to LED-based visible light/Cu(II)/H₂O₂ system, with total treatment cost estimated to be 80 ₹/m³ (0.9 €/m³ or 1.1 $/m³).

Singlet oxygen production abilities of oxidated aromatic compounds in natural water

Singlet oxygen (¹O₂) is well known to be formed through energy transfer from excited state organic matters to O₂, playing an important role in the transformations of contaminants. However, the contribution of small oxidated aromatic compounds (OACs) to the production of ¹O₂ in surface water is unclear. In this study, 28 OACs were selected to investigate the correlations between their photochemical production abilities of ¹O₂ and molecular structures. Our results showed that the steady-state concentrations and quantum yields of ¹O₂ (Φ_1O2) generated by OACs were in the range of 7.0 × 10^-14-1.4 × 10^-12 M and 2.2 × 10^-4-4.7 × 10^-2, respectively, indicating that the photochemical production abilities of ¹O₂ by OACs varied greatly with types and positions of functional groups on the molecule. More importantly, the observed photochemical production of ¹O₂ was most notable in cases of molecules containing -OCH₃ group and benzoquinone. A good quantitative structure-property relationship model was established between ¹O₂ producing ability, energy of the lowest unoccupied molecular orbitals (E_LUMO) and the most positive net charge of hydrogen atoms (qH⁺) of OACs. In addition, the role of ¹O₂ produced by 2, 6-dimethoxy-1, 4-benzoquinone, the OAC with the highest Φ_1O2, in the photodegradation of organic contaminants was validated by the enhanced degradation of atorvastatin under simulated sunlight, suggesting that OACs ubiquitously existed in surface water may greatly affect the fate and ecological risks of organic contaminants.

Recent advances in Cu-Fenton systems for the treatment of industrial wastewaters: Role of Cu complexes and Cu composites

Cu-based Fenton systems have been recognized as a promising suite of technologies for the treatment of industrial wastewaters due to their high catalytic oxidation capacity. Rapid progress regarding Cu Fenton systems has been made not only in fundamental mechanistic aspects of these systems but also with regard to applications over the past decade. Based on available literature, this review synthesizes the recent advances regarding both the understanding and applications of Cu-based Fenton processes for industrial wastewater treatment. Cu-based catalysts that are essential to the effectiveness of use of Cu Fenton reactions for oxidation of target species are mainly classified into two types: (i) Cu complexes with organic or inorganic ligands, and (ii) Cu composites with inorganic materials. Performance of the Cu-based catalysts for the removal of organic pollutants in industrial wastewaters are reviewed, with the key operating parameters illustrated. Furthermore, the roles of Cu complexes and composites in both homogeneous and heterogeneous Cu-Fenton systems are critically examined with particular focus on the mechanisms involved. Perspectives and future efforts needed for Cu-based Fenton systems using Cu complexes and composites for industrial wastewater treatment are presented.

In situ anodic induction of low-valence copper in electro-Fenton system for effective nitrobenzene degradation

To achieve superior advanced oxidation processes (AOPs), transitional state activators are of great significance for the production of active radicals by H₂O₂, while instability limits their activation efficiency. In this study, density functional theory calculation (DFT) results showed that Cu⁺ exhibits excellent H₂O₂ activation performance, with Gibbs free energy change (ΔG) of 33.66 kcal/mol, two times less than that of Cu²⁺ (77.83 kcal/mol). Meanwhile, an electro-Fenton system using Cu plate as an anode was proposed for in situ generation of Cu⁺. The released Cu with low-valence state can be well-confined on the surface of the exciting electrode, which was confirmed by X-ray photoelectron spectroscopy (XPS), Raman, and UV-vis spectroscopy. The hydroxyl radicals in this Cu-based electro-Fenton system were determined by the electron spin resonance (ESR). The nitrobenzene degradation ratio was greatly increased by 43.90% with the introduction of the proposed in situ electrochemical Cu⁺ generation process. Various characterization results indicated that the production of Cu⁺ was the key factor in the highly efficient Cu-based electro-Fenton reaction.

Fluoride ion accelerating degradation of organic pollutants by Cu(II)-catalyzed Fenton-like reaction at wide pH range

The degradation of rhodamine B in the F^-/Cu(II)/H₂O₂ system was studied to evaluate the accelerating effect of F^- on the Cu(II)-catalyzed Fenton-like reaction. Effects of various parameters, such as F^-/Cu²⁺ ratio, F^- and Cu²⁺ concentrations, initial pH, temperature, H₂O₂ and rhodamine B concentrations, were investigated. The results confirmed that there is a strong promoting effect of F^- on the Cu(II)-catalyzed Fenton-like reaction in a wide pH range of 4-11. In the F^-/Cu(II)/H₂O₂ system the dye could be degraded quickly, and H₂O₂ had a high utilization. A possible catalytical mechanism was proposed and CuF⁺ was assumed as the catalytically active species. CuF⁺ complexed with the OOH^- produced by H₂O₂ dissociation and then rapidly decomposed to Cu(I), which reacted with H₂O₂ generating hydroxyl radical (HO·), the major reactive oxidizing species.

Removal of triclosan in a Fenton-like system mediated by graphene oxide: Reaction kinetics and ecotoxicity evaluation

As a typical nanomaterial, graphene oxide (GO) can be easily dispersed in water and may affect the aqueous environment. In this paper, the degradation of triclosan (TCS) in a Fenton-like system Fe³⁺/H₂O₂ in GO aqueous solution was investigated. Interestingly, it was observed that GO at low concentration (2.0 mg/L) could exhibit significant catalytic effect on TCS removal. Meanwhile, results of XPS, Raman and TEM spectroscopy suggested the structure and chemical composition of GO did not exhibit significant change after the oxidation process within 30 min. As per the radical quenching experiments and ESR tests, hydroxyl radical (·OH) was mainly responsible for the decomposition of TCS. Further mechanism study indicated that the reaction activation energy (E_a) could be lowered and the production of ·OH be promoted in the presence of GO, respectively. A total of nine intermediates of TCS degradation were detected by TOF-LC-MS after SPE procedure. Finally, ecotoxicity assessment revealed that degradation of TCS by Fe³⁺/H₂O₂ system in GO aqueous solution could yield by-products of smaller toxicity compared with parent compounds.

Enhanced mineralization of hypersaline wastewater with Fe2+/Cu2+ catalyzed UV-Fenton process: process optimization and catalytic mechanism

The efficiency of Fenton oxidation was inhibited by the high content of salt in the industrial wastewater. However, enhanced mineralization of hypersaline industrial wastewater is necessary for advanced treatment and subsequent wastewater salt recovery process. Therefore, Fe²⁺ and Cu²⁺ catalyzed UV-Fenton oxidation were carried out to improve the total organic carbon (TOC) removal efficiency for a hypersaline wastewater from resin manufacturing. The performance of UV-Fe/Cu-Fenton oxidation was comparatively investigated and optimized using response surface methodology (RSM) to develop a practical high-efficient mineralization treatment technique for hypersaline wastewater. More than 90% of TOC was removed under optimal conditions of UV-Fe²⁺ and UV-Cu²⁺-Fenton oxidation, namely 9.6 mM Fe²⁺ and 176 mM H₂O₂, and 2.95 mM Cu²⁺ and 276 mM H₂O₂, respectively. The reactive oxygen radicals identified using electron spin resonance (ESR) spectroscopy revealed that hydroxyl radical was dominant oxidant in UV-Fe²⁺-Fenton process, while HO₂·/O₂·^- played a more important role in the UV-Cu-Fenton system. The Cl^- effect is also different for UV Fe and Cu Fenton. Moreover, no scaling and sludge problem makes UV-Cu-Fenton a promising alternative method for efficient mineralization of hypersaline industrial wastewater.

Silver nanoparticles or free silver ions work? An enantioselective phytotoxicity study with a chiral tool

Nowadays, silver nanoparticles (AgNP) have been widely used and there are raising concerns about their potential adverse effects on organism. As for the exact toxicity mechanism of AgNP, opinions still vary and whether the released silver ions (Ag⁺) or AgNP themselves are responsible for the toxicity remains debatable. In the present study, we have designed two exposure systems where Ag⁺ and AgNP coexisted but differed in quantification by using photo-reduced method with cysteine enantiomers, and their toxicities to freshwater microalgae Scenedesmus obliquus and model plant Arabidopsis thaliana were determined. In the results, Ag⁺ was in suit photo-reduced by cysteine enantiomers, and the UV-Vis and circular dichroism spectrum evidence confirmed the quantification difference between Ag-l-cysteine (Ag-l-Cys) and Ag-d-cysteine (Ag-d-Cys), where there was more AgNP and less Ag⁺ in Ag-l-Cys. Furthermore, the toxicity assay data revealed that Ag-d-Cys was more toxic to S. obliquus but A. thaliana was more susceptible to Ag-l-Cys. The metal element distribution in Arabidopsis leaves was also influenced in an enantioselective manner, which was related to the oxidative stress. Considering the quantification difference between Ag-l-Cys and Ag-d-Cys, it can be concluded that AgNP exhibited their toxicity to S. obliquus by the action of Ag⁺, but toxicity brought to A. thaliana was attributed to AgNP themselves rather than Ag⁺. The results of the present study help to better clarify the role of Ag⁺ in AgNP toxicity and offer a chiral tool and a new sight to investigate the toxicity mechanism of AgNP.

A review of quantitative structure-property relationships for the fate of ionizable organic chemicals in water matrices and identification of knowledge gaps

Many organic chemicals are ionizable by nature. After use and release into the environment, various fate processes determine their concentrations, and hence exposure to aquatic organisms. In the absence of suitable data, such fate processes can be estimated using Quantitative Structure-Property Relationships (QSPRs). In this review we compiled available QSPRs from the open literature and assessed their applicability towards ionizable organic chemicals. Using quantitative and qualitative criteria we selected the 'best' QSPRs for sorption, (a)biotic degradation, and bioconcentration. The results indicate that many suitable QSPRs exist, but some critical knowledge gaps remain. Specifically, future focus should be directed towards the development of QSPR models for biodegradation in wastewater and sediment systems, direct photolysis and reaction with singlet oxygen, as well as additional reactive intermediates. Adequate QSPRs for bioconcentration in fish exist, but more accurate assessments can be achieved using pharmacologically based toxicokinetic (PBTK) models. No adequate QSPRs exist for bioconcentration in non-fish species. Due to the high variability of chemical and biological species as well as environmental conditions in QSPR datasets, accurate predictions for specific systems and inter-dataset conversions are problematic, for which standardization is needed. For all QSPR endpoints, additional data requirements involve supplementing the current chemical space covered and accurately characterizing the test systems used.

A new five-coordinated copper compound for efficient degradation of methyl orange and Congo red in the absence of UV–visible radiation

A five-coordinated compound, Cu₂(2,2-bipy)₂(pfbz)₄, displays excellent properties of degrading methyl orange and Congo red in the absence of UV–visible radiation.