Multifunctional magnetic MgMn-oxide composite for efficient purification of Cd2+ and paracetamol pollution: Synergetic effect and stability

Interactions between microplastics (MPs) and trace/toxic metals in marine environments: implications and insights-a comprehensive review

Microplastics (MP) pollution is a pressing concern in today's marine environments. MPs can significantly affect marine ecosystems by altering nutrient and pollutant dynamics. This review analyses the existing literature to investigate interactions between MPs and micronutrients/pollutants, specifically trace and toxic metals in marine environments. It explores the adsorption of metals onto MP surfaces, emphasizing kinetics, isotherms, and underlying mechanisms of the process. The review highlights the potential consequences of MPs on the biogeochemical cycles of trace and toxic metals, emphasizing disruptions that could result in metal toxicity, metal limitations, reduced bioavailability, and adverse effects on primary productivity in marine ecosystems. It further underscores the need for future research to unravel the wide-ranging implications of MPs on trace and toxic metal cycling in marine ecosystems and their broader environmental impacts.

Applying Red Mud in Cadmium Contamination Remediation: A Scoping Review

Red mud is an industrial solid waste rarely utilized and often disposed of in landfills, resulting in resource waste and environmental pollution. However, due to its high pH and abundance of iron and aluminum oxides and hydroxides, red mud has excellent adsorption properties which can effectively remove heavy metals through ion exchange, adsorption, and precipitation. Therefore, red mud is a valuable resource rather than a waste byproduct. In recent years, red mud has been increasingly studied for its potential in wastewater treatment and soil improvement. Red mud can effectively reduce the migration and impact of heavy metals in soils and water bodies. This paper reviews the research results from using red mud to mitigate cadmium pollution in water bodies and soils, discusses the environmental risks of red mud, and proposes key research directions for the future management of red mud in cadmium-contaminated environments.

Eco-friendly natural mineral biotite as a cesium adsorbent: Utilizing low-concentration acid and hydrogen peroxide

Biotite, a phyllosilicate mineral, possesses significant potential for cesium (Cs) adsorption owing to its negative surface charge, specific surface area (SSA), and frayed edge sites (FES). Notably, FES are known to play an important role in the adsorption of Cs. The objectives of this study were to investigate the Cs adsorption capacity and behavior of artificially weathered biotite and identify mineralogical characteristics for the development of an eco-friendly geologically-based Cs adsorbent. Through various analyses, it was confirmed that the FES of biotite was mainly formed by mineral structural distortion during artificial weathering. The Cs adsorption capacity is improved by approximately 39% (from 20.53 to 28.63 mg g-1) when FES are formed in biotite through artificial weathering using a low-concentration acidic solution mixed with hydrogen peroxide (H2O2). Especially, the Cs selectivity in Cs-containing seawater, including high concentrations of cations and organic matter, was significantly enhanced from 203.2 to 1707.6 mL g-1, an increase in removal efficiency from 49.5 to 89.2%. These results indicate that FES of artificially weathered biotite play an essential role in Cs adsorption. Therefore, this simple and economical weathering method, which uses a low-concentration acidic solution mixed with H2O2, can be applied to natural minerals for use as Cs adsorbents.

Effective adsorption of Pb(ii) from wastewater using MnO2 loaded MgFe-LD(H)O composites: adsorption behavior and mechanism

Pb(ii) adsorption by MnO₂/MgFe-layered double hydroxide (MnO₂/MgFe-LDH) and MnO₂/MgFe-layered metal oxide (MnO₂/MgFe-LDO) materials was experimentally studied in lab-scale batches for remediation property and mechanism analysis. Based on our results, the optimum adsorption capacity for Pb(ii) was achieved at the calcination temperature of 400 °C for MnO₂/MgFe-LDH. Langmuir and Freundlich adsorption isotherm models, pseudo-first-order and pseudo-second-order kinetics, Elovich model, and thermodynamic studies were used for exploring the Pb(ii) adsorption mechanism of the two composites. In contrast to MnO₂/MgFe-LDH, MnO₂/MgFe-LDO_{400 °C} has a stronger adsorption capacity and the Freundlich adsorption isotherm model (R² > 0.948), the pseudo-second-order kinetic model (R² > 0.998), and the Elovich model (R² > 0.950) provide great fits to the experimental data, indicating that the adsorption occurs predominantly via chemisorption. The thermodynamic model suggests that MnO₂/MgFe-LDO_{400 °C} is spontaneously heat-absorbing during the adsorption process. The maximum adsorption capacity of MnO₂/MgFe-LDO_{400 °C} for Pb(ii) was 531.86 mg g^-1 at a dosage of 1.0 g L^-1, pH of 5.0, and temperature of 25 °C. Through characterization analysis, the main mechanisms involved in the adsorption process were precipitation action, complexation with functional groups, electrostatic attraction, cation exchange and isomorphic replacement, and memory effect. Besides, MnO₂/MgFe-LDO_{400 °C} has excellent regeneration ability in five adsorption/desorption experiments. The above results highlight the powerful adsorption capacity of MnO₂/MgFe-LDO_{400 °C} and may inspire the development of new types of nanostructured adsorbents for wastewater remediation.

Efficient Adsorption Capacity of MgFe-Layered Double Hydroxide Loaded on Pomelo Peel Biochar for Cd (II) from Aqueous Solutions: Adsorption Behaviour and Mechanism

A novel pomelo peel biochar/MgFe-layered double hydroxide composite (PPBC/MgFe-LDH) was synthesised using a facile coprecipitation approach and applied to remove cadmium ions (Cd (II)). The adsorption isotherm demonstrated that the Cd (II) adsorption by the PPBC/MgFe-LDH composite fit the Langmuir model well, and the adsorption behaviour was a monolayer chemisorption. The maximum adsorption capacity of Cd (II) was determined to be 448.961 (±12.3) mg·g^-1 from the Langmuir model, which was close to the actual experimental adsorption capacity 448.302 (±1.41) mg·g^-1. The results also demonstrated that the chemical adsorption controlled the rate of reaction in the Cd (II) adsorption process of PPBC/MgFe-LDH. Piecewise fitting of the intra-particle diffusion model revealed multi-linearity during the adsorption process. Through associative characterization analysis, the adsorption mechanism of Cd (II) of PPBC/MgFe-LDH involved (i) hydroxide formation or carbonate precipitation; (ii) an isomorphic substitution of Fe (III) by Cd (II); (iii) surface complexation of Cd (II) by functional groups (-OH); and (iv) electrostatic attraction. The PPBC/MgFe-LDH composite demonstrated great potential for removing Cd (II) from wastewater, with the advantages of facile synthesis and excellent adsorption capacity.

Photocatalytic Degradation of Paracetamol under Simulated Sunlight by Four TiO2 Commercial Powders: An Insight into the Performance of Two Sub-Micrometric Anatase and Rutile Powders and a Nanometric Brookite Powder

The photocatalytic degradation of the emerging contaminant paracetamol in aqueous solution has been studied under 1 SUN (~1000 W m−2) in the presence of four commercial TiO2 powders, namely sub-micrometric anatase and rutile, and nanometric brookite and P25 (the popular anatase/rutile mixture used as a benchmark in most papers). The rutile powder showed low activity, whereas, interestingly, the anatase and the brookite powders outperformed P25 in terms of total paracetamol conversion to carboxylic acids, which, according to the literature, are the final products of its degradation. To explain such results, the physicochemical properties of the powders were studied by applying a multi-technique approach. Among the physicochemical properties usually affecting the photocatalytic performance of TiO2, the presence of some surface impurities likely deriving from K3PO4 (used as crystallization agent) was found to significantly affect the percentage of paracetamol degradation obtained with the sub-micrometric anatase powder. To confirm the role of phosphate, a sample of anatase, obtained by a lab synthesis procedure and having a “clean” surface, was used as a control, though characterized by nanometric particles and higher surface area. The sample was less active than the commercial anatase, but it was more active after impregnation with K3PO4. Conversely, the presence of Cl at the surface of the rutile did not sizably affect the (overall poor) photocatalytic activity of the powder. The remarkable photocatalytic activity of the brookite nanometric powder was ascribed to a combination of several physicochemical properties, including its band structure and nanoparticles size.

Potential Mechanism of Long-Term Immobilization of Pb/Cd by Layered Double Hydroxide Doped Chicken-Manure Biochar

Layered double hydroxide (LDH)-doped chicken-manure biochar (CMB) with long-term stability was synthesized to immobilize Pb/Cd. MgAl-Cl-LDH-doped CMB (MHs) showed prominent long-term oxidation resistance and the least biodegradation sensitivity. Efficient Pb/Cd adsorption was observed on MHs, and the maximum adsorption capacities of Pb(II)/Cd(II) reached 1.95 mmol/g and 0.65 mmol/g, respectively. Precipitation and isomorphous substitution were identified as the key adsorption mechanisms, which formed highly stable Pb/Cd species (PbAl-CO₃-LDH, Pb₃(OH)₂CO₃, CdAl-Cl-LDH and CdCO₃). Pb(II) and Cd(II) precipitated with CO₃^2- in MHs; meanwhile, Mg(II) and Ca(II) in LDH layers were substituted by Pb(II) and Cd(II) respectively. Therefore, MHs had the potential for long-term stability of Pb/Cd. Moreover, complexation and electrostatic adsorption also contributed to the Pb/Cd immobilization to a certain extent. When 5% MHs (w/w) was applied to Pb/Cd contaminated smelting site soils, the soil pH increased from 5.9 to 7.3. After applying MHs for 25 d, the content of bioavailable Pb(II) and Cd(II) decreased by 98.8% and 85.2%, respectively, and the content of soluble Pb and Cd dropped by 99.5% and 96.7%. This study paves the way for designing a novel LDH doped CMB as efficient Pb/Cd immobilizers for smelting site soils.

A tailored bifunctional carbon catalyst for efficient glycosidic bond fracture and selective hemicellulose fractionation

This study proposed a mild chlorination-sulfonation approach to synthesize magnetic carbon acid bearing with catalytic SO₃H and adsorption Cl bifunctional sites on polydopamine coating. The catalysts exerted good textural structure and surface chemical properties (i.e., porosity, high specific surface area of >70 m²/g, high catalytic activity with 0.86-1.1 mmol/g of SO₃H sites and 0.8%-1.9% of Cl sites, and abundant hydrophilic functional groups), rendering a maximum cellobiose adsorption efficiency of ∼40% within 6 h. Moreover, the catalysts had strong fracture characteristics on different α-/β-glycosidic bonds with 85.4%-93.9% of disaccharide conversion, while selectively fractionating hemicellulose from wheat straw with 64.3% of xylose yield and 93.4% of cellulose retention. Due to the stable interaction between parent polydopamine support with Fe core and functional groups, the catalysts efficiently recovered by simple magnetic separation had good reusability with minimal losses in catalytic activity.

Sustainable Mitigation of Paracetamol with a Novel Dual-Functionalized Pullulan/Kaolin Hydrogel Nanocomposite from Simulated Wastewater

In the present investigation, a novel, green, and economical dual-functionalized pullulan/kaolin hydrogel nanocomposite (f-PKHN) was fabricated and subsequently applied for the liquid-phase decontamination of paracetamol (PCT), a pharmaceutical pollutant. Pullulan and kaolin were functionalized with l-asparagine and gallic acid, respectively. The physicochemical facets of the functionalized pullulan/kaolin hydrogel nanocomposite and its interactive behavior with PCT were elucidated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), and elemental mapping. The process parameters along with the isotherm, kinetics, and thermodynamics were methodically appraised via a batch technique to unveil the adsorption performance of the as-fabricated hydrogel nanocomposite. The adsorption isotherm and kinetics of PCT uptake by f-PKHN conform well to Freundlich and pseudo-second-order models, respectively. Relying on hydrogen bonding, n-π, and van der Waals interactions, the maximum adsorption capacity was 332.54 mg g^-1, higher than for most of the previous adsorbents reported in the literature for PCT removal. Thermodynamic calculations corroborated endothermic, spontaneous, and feasible adsorption phenomena. The maintenance of a high uptake percentage (69.11%) in the fifth consecutive adsorption-desorption cycle implied the significant reusable potential of f-PKHN. Swelling studies exhibited 90% swelling within 200 min, indicating the successful fabrication of a cross-linked hydrogel network. The real water (distilled water, tap water, and river water) samples spiked with PCT specified a significant uptake of PCT (>85%), and the minor influence of ionic strength on the adsorptive potential of f-PKHN validated its potentiality for the decontamination of real effluents. In conclusion, f-PKHN with substantial adsorption capacity, green characteristics, and excellent reusability can be reckoned with as a promising adsorbent for the de-escalation of PCT from aquatic sources as well as at the industrial level.

A Comprehensive Review of Layered Double Hydroxide-Based Carbon Composites as an Environmental Multifunctional Material for Wastewater Treatment

As is well known, hydrotalcite-like compounds, such as layered-double-hydroxide (LDH) materials, have shown great potential applications in many fields owing to their unique characteristics, including a higher anion exchange capacity, a structure memory effect, low costs, and remarkable recyclability. While the lower surface area and leaching of metal ions from LDH composites reduce the process efficiency of the catalyst, combining LDH materials with other materials can improve the surface properties of the composites and enhance the catalytic performance. Among organic compounds, carbon materials can be used as synergistic materials to overcome the defects of LDHs and provide better performance for environmental functional materials, including adsorption materials, electrode materials, photocatalytic materials, and separation materials. Therefore, this article comprehensively reviews recent works on the preparation and application of layered double-hydroxide-based carbon (LDH–C) composites as synergistic materials in the field of environmental remediation. In addition, their corresponding mechanisms are discussed in depth. Finally, some perspectives are proposed for further research directions on exploring efficient and low-cost clay composite materials.

Enhanced selective adsorption of lead(II) from complex wastewater by DTPA functionalized chitosan-coated magnetic silica nanoparticles based on anion-synergism

Simultaneously removing heavy metal and dye from complex wastewater is of great significance to industrial wastewater treatment. Herein, a novel magnetic adsorbent, DTPA-modified chitosan-coated magnetic silica nanoparticle (FFO@Sil@Chi-DTPA), was successfully prepared and used to enhance the Pb(II) selective adsorption from multi-metal wastewater based on anion-synergism. In the competitive experiment conducted in a multi-ion solution, the type of selective adsorption of metals was changed by the adsorbents before and after amidation, in which FFO@Sil@Chi-DTPA exhibited an excellent selectively for capturing Pb(II), while FFO@Sil@Chi demonstrated highly selective adsorption of silver. More importantly, the selective adsorption of Pb(II)S by FFO@Sil@Chi-DTPA was enhanced from 111.71 to 268.01 mg g^-1 when the coexisting MB concentrations ranged from 0 to 100 mg L^-1 at pH 6.0. In the Pb(II)-MB binary system, Pb(II) and MB exhibited a synergistic effect, in which the presence of MB strengthened the adsorption effect of Pb(II) due to the sulfonic acid groups in MB molecules that create new specific sites for Pb(II) adsorption, while MB adsorption was also enhanced by the presence of Pb(II). This work provides a new strategy for exploring novel adsorbents that can enhance the selective removal of heavy metal in complex wastewater based on anion-synergism.

Simultaneous oxidation and removal of arsenite by Fe(III)/CaO2 Fenton-like technology

Arsenite contaminated water is one of severe global environmental problems. It is challenging to treat As(III) pollution by a one-step technology. In this study, we developed a Fe(III)/CaO₂ Fenton-like technology for the treatment of As(III). The simultaneous oxidation of arsenite and removal of arsenic were achieved with efficiencies of nearly 100% and 95.8% respectively, which outperforms conventional technologies. It worked well in pH 3 to 9, and in the presence of cationic heavy metals, anions and humic acid. Moreover, the PO₄^3- inhibited the removal of As(III). •OH and ¹O₂ played the important roles in the oxidation of As(III). The Ca(II) derived from CaO₂ made a significant contribution to the oxidation and removal of As(III). The SEM and XPS studies confirmed that the formation of Ca-Fe nascent colloid caused the effective removal of arsenic. Our study demonstrates that the one-step Fe(III)/CaO₂ technology has a great potential for purification of the As(III)-contaminated water.

Effective cesium removal from Cs-containing water using chemically activated opaline mudstone mainly composed of opal-cristobalite/tridymite (opal-CT)

Opaline mudstone (OM) composed of opal-CT (SiO2·nH2O) has high potential use as a cesium (Cs) adsorbent, due to its high specific surface area (SSA). The objective of this study was to investigate the Cs adsorption capacity of chemically activated OM and the adsorption mechanism based on its physico-chemical properties. We used acid- and base-activation methods for the surface modification of OM. Both acid- and base- activations highly increased the specific surface area (SSA) of OM, however, the base-activation decreased the zeta potential value more (- 16.67 mV), compared to the effects of acid-activation (- 6.60 mV) or non-activation method (- 6.66 mV). Base-activated OM showed higher Cs adsorption capacity (32.14 mg/g) than the others (acid: 12.22 mg/g, non: 15.47 mg/g). These results indicate that base-activation generates pH-dependent negative charge, which facilitates Cs adsorption via electrostatic attraction. In terms of the dynamic atomic behavior, Cs cation adsorbed on the OM mainly exist in the form of inner-sphere complexes (IS) containing minor amounts of water molecules. Consequently, the OM can be used as an effective Cs adsorbent via base-activation as an economical and simple modification method.

Red mud based passivator reduced Cd accumulation in edible amaranth by influencing root organic matter metabolism and soil aggregate distribution

Red mud was a highly alkaline hazardous waste, and their resource utilization was a research hotspot. In this study, influencing mechanisms of red mud based passivator on the transformation of Cd fraction in acidic Cd-polluted soil, photosynthetic property, and Cd accumulation in edible amaranth were investigated based on the evaluation of Cd adsorption capacity, root metabolic response, and soil aggregate distribution. Results showed that red mud exhibited good Cd adsorption capacities at about 35 °C and pH 9 in an aqueous solution, and the adsorption behavior of red mud on Cd in rhizosphere soil solution was considered to have some similarity. In the soil-pot trial, red mud application significantly facilitated edible amaranth growth by enhancing the maximum photochemical efficiency and light energy absorption by per unit leaf area by activating more reaction centers. The main mechanisms of rhizosphere soil Cd immobilisation by red mud application included: i) the reduction of mobilized Cd caused by the increasing negative surface charge of soil and precipitation of Cd hydroxides and carbonates at high pH; ii) the increase of organics-Cd complexes caused by the increasing -OH and -COOH amounts adsorbed on the surface of rhizosphere soil after red mud application; and iii) the decrease of available Cd content in soil aggregates caused by the increasing organic matters after red mud application. This study would provide the basis for the safe utilization of red mud remediating acidic Cd-polluted soil.

Preparation of magnetic biochar and its application in catalytic degradation of organic pollutants: A review

In recent years, magnetic biochar (MBC) has been greatly concerned because of its magnetic separation characteristics, and has been successfully used as a catalyst in the catalytic degradation of organic pollutants. However, there is currently a lack of a more systematic summary of MBC preparation methods, and no detailed overview of the catalytic mechanism of MBC catalysts for the degradation of organic pollutants. Therefore, we carry out this work to fill the above gaps. At first, we summarize the raw materials, preparation methods, and types of MBC in detail, and emphasize the MBC prepared by iron-containing sludge. Then, the catalytic mechanisms of MBC in peroxydisulfate, peroxymonosulfate, Fenton-like, photocatalysis, and NaBH₄ systems are carefully summarized, highlighting the contribution of various parts of MBC in catalysis. The degradation efficiency of organic pollutants in the above systems is evaluated. Finally, the stability and reusability of MBC catalysts are evaluated. In conclusion, this review contributes a meager force to the future development of MBC.

Hybrid MnFe-LDO-biochar nanopowders for degradation of metronidazole via UV-light-driven photocatalysis: Characterization and mechanism studies

A cost-competitive MnFe-LDO-biochar hybrid catalyst was successfully synthesized via a simple yet efficient technique for the decomposition of metronidazole (MZ). MnFe-LDO-biochar was characterized by various techniques and the results revealed that it has a bandgap of 2.85 eV, high photocurrent response of 3.8 μA cm^-2 and can be separated rapidly from the bulk solution by an external magnet due to its saturation magnetization of 28.5 emu g^-1. Initially, in the dark condition, 20% of MZ was removed after 30 min when 20 mg L^-1 MZ solution was treated with 50 mg MnFe-LDO-biochar in the presence of 6 mM H₂O₂. The MZ degradation increased remarkably to ∼98% upon exposure to a UV light for 60 min. Under various processes, UV/MnFe-LDO-biochar/H₂O₂ presented high degradation rate constant of 0.226 min^-1 and lowest energy consumption cost of 0.38$ at 7.56 kWh m^-3 which is ∼13 times lower than the degradation of MZ by the photolytic process under similar conditions. The MZ photocatalytic decomposition trend revealed a multiprocess mechanism influenced majorly by ^•OH and partly by h⁺ and ^•O₂^-. Note that in MnFe-LDO-biochar/UV system; 5% of MZ degradation was observed after 120 min and reached 13% after 300 min. MnFe-LDO-biochar maintained ∼88% reuse efficiency after three consecutive recycling tests.

Cesium removal using acid- and base-activated biotite and illite

Biotite and illite have excellent cesium (Cs) adsorption capacity due to their negative charges in addition to adsorption sites of the planar, interlayer, and frayed edge sites (FES). The aim of this study is to investigate the Cs adsorption capacity using acid- and base-activated biotite and illite based on their mineralogical characteristics. The acid-activated biotite and base-activated illite exhibited high Cs removal efficiency from the low-level Cs-containing DI water (97.5 % and 97.3 %, respectively). The acid-activation of biotite increased the specific surface area (SSA, 12.08 → 43.04 m²/g), Fe(III)/Fe(II) ratio (0.56 → 0.76), and wedge zone d-spacing (1.017 → 1.065 nm), while the zeta potential (-4.06 → -4.82 mV) decreased. The base-activation of illite resulted to a decrease in the SSA (22.14 → 18.49 m²/g), zeta potential (-7.68 → -31.64 mV), and Fe(III)/Fe(II) ratio (0.92 → 0.79). However, only acid-activated biotite appeared to have a high capacity of Cs removal from Cs-containing seawater (73.9 %; base-activated illite: 26.1 %). These results indicate that the FES of biotite owing to acid-activation showed better results in regards to Cs adsorption as compared to the pH-dependent negative charges of the base-activated illite.

Enhanced electrochemical degradation of 2,4-dichlorophenol with the assist of hydrochar

Effective treatment of 2,4-dichlorophenol (2,4-DCP) in wastewater is essential, as it could pose great threat to the environment. A hydrothermal biochar (hydrochar) was used to assist the electrochemical oxidation treatment of 2,4-DCP. The removal of 2,4-DCP using hydrochar in anode and cathode area with and without proton exchange membrane (PEM) under 3-9 V of electrolysis was investigated. Enhanced 2,4-DCP degradation in the anode area was achieved compared with the adsorption or electrolysis alone. The highest 2,4-DCP removal (∼76%) was obtained using the hydrochar in the anode area with PEM under 9 V. The mechanism for the 2,4-DCP removal during the electrolysis included adsorption by hydrochar and electrochemical degradation by the reactive oxygen species (ROS) generated by the electrode as well as the persistent free radicals (PFR) on hydrochar. The OH produced from anode was the predominant ROS contributing to the 2,4-DCP degradation under 9 V of electrolysis.

Highly selective removal of Ni(II) from plating rinsing wastewaters containing [Ni-xNH3-yP2O7]n complexes using N-chelating resins

Inorganic complexants, such as ammonia (AA) and pyrophosphate (PP), are often present alongside heavy metal ions in alkaline plating rinsing wastewater. We investigated the removal capacity of Ni(II) from waters containing [Ni-xNH₃-yP₂O₇]ⁿ complexes by chelating and ion-exchange resins in sole and dual-ligand systems. D463 (containing iminodiacetic groups) and PAMD (possessing polyamine groups) exerted superior performance under all conditions. Ni(II) adsorption on D463 decreased with AA and PP by 10.3% and 64.4%, respectively. Conversely, the adsorption on PAMD increased by 57.3% and 75.8%, respectively. PAMD exhibited high selectivity toward anionic [Ni-PP] species over free PP. More Ni(II) was captured by PAMD in the dual-ligand systems than sole systems, while the case for D463 was opposite. As confirmed by species tracking and DFT/XPS analyses, complexes breaking-Ni²⁺ capture was the dominant mechanism for D463, while the dual-site (non-charged and protonated amines) interactions with NiP₂O₇^2- on PAMD promoted its adsorption. The tandem combination D463-PAMD was the optimal mode to remove the most Ni(II). The actual wastewater test demonstrated that >210 BV effluent met the limit of 0.1 mg Ni(II)/L and the eluent contained 15 g Ni(II)/L. This study guides the application of chelating adsorption processes in the advanced treatment of plating rinsing wastewaters.

The obvious advantage of amino-functionalized metal-organic frameworks: As a persulfate activator for bisphenol F degradation

In this study, two iron-based metal-organic framework compounds (MOFs), were used and compared as catalysts for persulfate (PS) activation to degrade bisphenol F (BPF). The outstanding advantage of using amino-functionalized MOFs in the catalytic system was verified under different reaction conditions, and the mechanism was explored. The results indicated that NH₂-MIL-101(Fe)/PS system not only had a wide pH application range, but also possessed an excellent catalytic performance towards interference from the coexisting anions and humic acid. Density functional theory (DFT) calculations showed that, compared with MIL-101(Fe), the -NH₂ modification could significantly improve the electronic conductivity of NH₂-MIL-101(Fe) by enhancing its Fermi level (-4.28 eV) and binding energy to PS (-1.19 eV). The free radical quenching experiments were combined with electron paramagnetic resonance (EPR) confirmed that free radicals (SO₄^-, OH, O₂^-) worked together with the non-radical (¹O₂) reaction to remove 91% BPF within 40 min in the NH₂-MIL-101(Fe)/PS system. The two proposed BPF degradation pathway were related to hydroxylation, oxidation and ring cracking. The toxicity of the BPF degradation intermediates as well as its final products were also evaluated.

Simultaneous removal of Cr(VI) and acid orange 7 from water in pyrite-persulfate system

As the industries advances at a fast pace, efficient and simultaneous removal of both heavy metals and organics from aqueous is essential to protecting public human health and environment. In this work, we used pyrite as reductant and catalyst for simultaneously reducing Cr(VI) and activating persulfate (PS) to degrade acid orange 7 (AO7). The results indicated that the simultaneous removal rate of AO7 and Cr(VI) by pyrite-PS was up to 100% within 60 min under acidic conditions. However, There was a competitive relationship between PS activation and Cr(VI) reduction for robbing Fe²⁺. At beginning of the reaction, the limited Fe²⁺ firstly activated persulfate rather than reduce Cr(VI). The effect of dosage of pyrite and PS on Cr(VI) reduction was more significant than that on AO7 degradation. Increased pyrite dosages from 1g·L^-1 to 6 g L^-1 resulted in enhanced Cr(VI) removal, and excessive PS (more than 0.4 g L^-1) was not beneficial to Cr(VI) removal. Electron paramagnetic resonance (EPR) spectroscopy and radical scavenger studies demonstrated that sulfate (SO₄^-·), singlet oxygen (¹O₂) and superoxide radical (·O₂^-) were the crucial reactive oxygen species (ROS) in the pyrite-PS system rather than hydroxyl radical (·OH). This study showed that the pyrite-PS system could simultaneously remove AO7 and Cr(VI), which provided a new idea for the actual wastewater treatment.

Nano-FeS incorporated into stable lignin hydrogel: A novel strategy for cadmium removal from soil

Strategies for reducing cadmium (Cd) content in polluted farmland soils are currently limited. A type of composite with nanoparticles incorporated into a hydrogel have been developed to efficiently remove heavy metals from sewage, but their application in soils faces challenges, such as organic hydrogel degradation due to oxygen exposure and slow Cd²⁺ release from soil constituents. To overcome these challenges, a composite with superior stability for long-term application in soil is required. In this study, ferrous sulfide (FeS) nanoparticle@lignin hydrogel composites were developed. The lignin-based hydrogels inherited lignin's natural mechanical and environmental stability and the FeS nanoparticles efficiently adsorbed Cd²⁺ and enhanced Cd²⁺ desorption from soils by producing H⁺. The high sorption capacity (833.3 g kg^-1) of the composite was attributed to four proposed mechanisms, including cadmium sulfide (CdS) precipitation via chemical reaction (84.06%), lignin complexation (13.19%), hydrogel swelling (0.61%), and nanoparticle sorption (2.15%). In addition, Fe²⁺ displaced from the composite was gradually oxidized to form solid iron oxide hydroxide, which increased Cd²⁺ sorption. The composite significantly reduced the total, surfactant-soluble, and fixed Cd in heavily and lightly polluted paddy soils by 22.4-49.6%, 13.5-68.6%, and 40.1-16.6%, respectively, in 7 days.