Water Remediation Research Articles

Innovative ternary composite photocatalyst: BiOCl/Bi12O17Cl2/Bi2O3 for sustainable water remediation

The presence of pollutants in aquatic environments is causing severe health effects on both humans and animals. To address this issue, it has become crucial to develop more efficient and environmentally friendly photocatalysts for the removal of persistent pollutant mixtures from water. In this context, photocatalysts containing more than two bismuth-based materials have rarely been explored for water remediation. With this in mind, we propose an innovative ternary composite, BiOCl-1/Bi12O17Cl2/Bi2O3, as a potentially sustainable visible light-active photocatalyst. Firstly, bismuth oxychloride has been prepared in the presence of ionic liquid, leading to the formation of BiOCl-1 with highly reactive {110} facets. Subsequently, the construction of the ternary composite has been accomplished using a facile and soft hydrothermal approach. The as-prepared BiOCl-1/Bi12O17Cl2/Bi2O3 composite has been successfully used in degrading binary mixtures of contaminants (i.e. ciprofloxacin, methylparaben or methyl orange), achieving an improved visible-light photocatalytic activity compared to single BiOCl-1 and other previously reported bismuth-based photocatalysts. In addition, the photocatalytic mechanism and degradation pathways have been elucidated through scavenger and electrochemical experiments, as well as chromatography-mass spectrometry (LC-MS) analysis, respectively.

Enhancing Pb2+ removal efficiency in flow-through systems using flue gas desulfurization gypsum-based porous materials: Experimental and numerical studies

This study addresses the poor permeability of flue gas desulfurization (FGD) gypsum in water remediation and further explores its potential for resource utilization. FGD gypsum-based porous materials (FGPMs) were prepared using different foaming behavior as permeable reactive barrier (PRB) media materials. The dynamic removal performance of Pb2+ was investigated, and a numerical model was developed to validate the results. The findings reveal that the adsorption mechanisms of FGPMs primarily involve ion exchange and surface precipitation. Pb2+ does not alter the structure or functional groups of the materials. By optimizing the foaming behavior to enhance pore connectivity, the adsorption capacity increased from 8.78 mg/g to 13.42 mg/g, thereby extending the service life of the PRB. The presence of closed and capillary pores hinders the dynamic removal performance of Pb2+. Furthermore, the FGPMs exhibit superior removal performance at low flow rates, low concentrations, and high column heights, as confirmed by the numerical model. These results offer valuable insights for designing and optimizing FGD gypsum-based adsorption processes to remove Pb2+ from wastewater efficiently.

Graphene oxide–carbon nanotube composite membrane for enhanced removal of organic pollutants by forward osmosis

Composite membranes constructed using both graphene oxide and carbon nanotubes (CNTs) were designed to strengthen the forward osmosis (FO) technology for the removal of organic contaminants. The nano-membrane was chemically treated with organic acids, which were citric acid in this case for more efficiency in permeability and pollutant removal. The efficiency of the composite membranes in organic pollutants removal was estimated by checking the levels of COD (chemical oxygen demand), TKN (total nitrogen analysis), and (TOC) organic carbon in the water sample before and after applying the technology. The analysis of the study recommends that the nano-membranes may be appropriately used to reduce organic pollutants significantly, to 98.20% efficiency, in addition to elevating water quality standards. This was caused by the higher degree of selectivity and permeability of the membranes that was consequent to the treatment of the organic acid. In brief, the employment of citric acid in the pre-treatment procedures for the preparation of composite graphene oxide-carbon nanotube membranes for FO technology could take water cleaning technologies a step ahead toward sustainable technology. The application of the composite membrane with graphene oxide and carbon nanotubes is not only efficient in cleaning out organic contaminants but it has a lot of added benefits. These membranes are easily manufactured with a long lifespan which, in turn, makes them cost-effective and environmentally friendly. Also, forward osmosis technology reduces the energy demand compared to other water remediation methods, making it a more sustainable solution. The final point of this article is that the using of composite graphene oxide-carbon nanotube membranes treated with an organic acid, such as citric acid, in FO technology not only assists with the water treatment problem but also elevates sustainablility due to its effectiveness and is environmentally friendly.

Enhanced photodegradation of ciprofloxacin antibiotic using ZnO@FAU composite: A promising material for contaminant removal

In this work, Faujasite zeolite (FAU) was used as support for photoactive ZnO particles, which were prepared by in situ assembly to zeolite as photocatalyst to degrade emerging organic pollutants like pharmaceuticals in water bodies. Physicochemical characterization techniques such as PXRD, FTIR, solid-state NMR, N2 adsorption-desorption, SEM, and DRS-UV revealed good compatibility between the inorganic components, resulting in intriguing surface properties for chemical reactions. This material efficiently degraded the antibiotic ciprofloxacin, showing a significant removal rate of 92% within 90 min under UV light due to a cooperative effect between FAU and ZnO. The photocatalytic process followed a direct mechanism, where h+ plays a crucial role in oxidizing the drug molecules adsorbed on the catalyst surface. In addition to pharmaceuticals, the ZnO@FAU composite was also employed in the photodecolorization of Indigo Carmine and Rhodamine B dyes, revealing a removal of 100% and 99%, respectively. These results showcase this composite's versatility in tackling different pollutants, positioning it as a promising material for water remediation.

Scallop shells as biosorbents for water remediation from heavy metals: Contributions and mechanism of shell components in the adsorption of cadmium from aqueous matrix

To ascertain their potential for heavy metal pollution remedy, we studied the adsorption mechanism of cadmium onto scallop shells and the interactions between the heavy metal and the shell matrix. Intact shells were used to investigate the uptake and diffusion of the metal contaminant onto the shell carbonatic layers, as well as to evaluate the distribution of major and trace elements in the matrix. LA-ICPMS measurements demonstrate that Cd is adsorbed on a very thin layer on the inner and outer surfaces of the shell. Structural and thermal analyses showed the presence of 9 wt.-% of a CdCO3 phase indicating that the adsorption is mainly a superficial process which involves different processes, including ion exchange of Ca by Cd. In addition, organic components of the shell could contribute to adsorption as highlighted by different metal uptake observed for shells with different colours. In particular, darker shells appeared to adsorb more contaminant than the white ones. The contribution of the organic shell components on the adsorption of heavy metals was also highlighted by the element bulk content which showed higher concentrations of different metals in the darker specimen. Raman spectroscopy allowed to identify the pigments as carotenoids, confirmed by XRD measurements which highlighted the presence of astaxanthin phases. The results presented here provide new insights into the Cd adsorption mechanism highlighting the important contribution given by the organic components present in the biogenic carbonate matrix. Furthermore, the high efficiency of Cd removal from water by scallop shells, supported by adsorption kinetic and isotherm studies, has been demonstrated.

Development of a novel pH-Responsive PVA/GO-Glu/TiO2 nanocomposite hydrogel for efficient degradation of organic pollutants

Water pollution poses a grave threat to public health and the environment. There is an urgent need for sustainable remediation strategies to remove toxic contaminants from water sources. In this study, we report the development of a novel pH-responsive nanocomposite hydrogel for the effective degradation of organic pollutants. The hydrogel was synthesized using polyvinyl alcohol, graphene oxide, glutamic acid, and titanium dioxide through an in-situ crosslinking method. Characterization using SEM, FTIR and UV–vis spectroscopy confirmed the successful formation of the nanocomposite structure. Batch experiments demonstrated that the hydrogel was able to degrade over 90% of methylene blue dye within 35 min under sunlight irradiation, owing to the synergistic effect of pH-sensitivity and the photocatalytic activity of titanium dioxide. Degradation efficiency increased with rising pH, reaching a maximum at pH 11. This eco-friendly nanohybrid holds tremendous potential for water remediation applications through low-cost, solar-powered degradation of toxic pollutants.

Molecular Weight-Independent "Polysoap" Nanostructure Characterized via In Situ Resonant Soft X-ray Scattering.

Studying polymer micelle structure and loading dynamics under environmental conditions is critical for nanocarrier applications but challenging due to a lack of in situ nanoprobes. Here, the structure and loading of amphiphilic polyelectrolyte copolymer micelles, formed by 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and n-dodecyl acrylamide (DDAM), were investigated using a multimodal approach centered around in situ resonant soft X-ray scattering (RSoXS). We observe aqueous micelles formed from polymers of wide-ranging molecular weights and aqueous concentrations. Despite no measurable critical micelle concentration (CMC), structural analyses point toward multimeric structures for most molecular weights, with the lowest molecular weight micelles containing mixed coronas and forming loose micelle clusters that enhance hydrocarbon uptake. The sizes of the micelle substructures are independent of both the concentration and molecular weight. Combining these results with a measured molecular weight-invariant surface charge and zeta potential strengthens the link between the nanoparticle size and ionic charge in solution that governs the polysoap micelle structure. Such control would be critical for nanocarrier applications, such as drug delivery and water remediation.

Evaluation of the Swelling Properties and Sorption Capacity of Maltodextrin-Based Cross-Linked Polymers.

The development of polymers obtained from renewable sources such as polysaccharides has gained scientific and industrial attention. Cross-linked bio-derived cationic polymers were synthesized via a sustainable approach exploiting a commercial maltodextrin product, namely, Glucidex 2®, as the building block, while diglycidyl ethers and triglycidyl ethers were used as the cross-linking agents. The polymer products were characterized via FTIR-ATR, TGA, DSC, XRD, SEM, elemental analysis, and zeta-potential measurements, to investigate their composition, structure, and properties. Polydispersed amorphous granules displaying thermal stabilities higher than 250 °C, nitrogen contents ranging from 0.8 wt % and 1.1 wt %, and zeta potential values between 10 mV and 15 mV were observed. Subsequently, water absorption capacity measurements ranging from 800% to 1500%, cross-linking density determination, and rheological evaluations demonstrated the promising gel-forming properties of the studied systems. Finally, nitrate, sulfate, and phosphate removal tests were performed to assess the possibility of employing the studied polymer products as suitable sorbents for water remediation. The results obtained from the ion chromatography technique showed high sorption rates, with 80% of nitrates, over 90% of sulfates, and total phosphates removal.

Fe2O3-Kao@g-CN activated peroxymonosulfate remediation of bensulfuron methyl-polluted water and soil: Detoxification, soil properties and crop growth

Peroxymonosulfate-based advanced oxidation processes (PMS-AOPs) have been frequently applied in environment remediation for the rapid degradation of organics, while the high PMS usage could increase economic cost and ecological risks. Therefore, efficient activation methods are highly needed. In this study, low cost and environmentally safe bi-mineral hybrid carbon Fe2O3-Kao@g-CN was designed and fabricated to efficiently activate PMS for the remediation of water and soil polluted by bensulfuron methyl (BSM). Specifically, the Fe2O3-Kao@g-CN/PMS system could utterly remove BSM from water within 90 min and showed satisfactory tolerance to environment variation. The toxic BSM could be degraded into 15 kinds of intermediates with lower toxicity, benefiting from various reactive species of SO4•−, O2•−, •OH and 1O2. Furthermore, the removal efficiency of BSM in polluted wheat and maize soil reached about 79.2 %-86.8 % with low doses of PMS (3.07 mg·g−1) and catalyst (2 %). The degradation system did not adversely affect the soil pH and the soil redox potential (Eh), while promoted soil potassium availability and crop growth. The biomass and length of wheat and maize in remediated soil was significantly increased by 26.2 %-346.4 % compared with those planted in BSM-contaminated soil. This work emphasized the application of Fe2O3-Kao@g-CN/PMS system for BSM detoxification in water and soil and its ecological risks, offering a theoretical and practical foundation for decreasing environment risk and ensuring crop growth in the environment remediation.

MnFe layered double hydroxides confined MnOx for peroxymonosulfate activation: A novel manner for the selective production of singlet oxygen

Singlet oxygen (1O2) is a reactive species for the selective degradation of stubborn organic pollutants. Given its resistance to harsh water environment, the effective and exclusive generation of 1O2 is acknowledged as a key strategy to mitigate water production costs and ensure water supply safety. Herein, we synthesized MnOx intercalated MnFe layered double hydroxides (MF-MnOx) to selectively produce 1O2 through the activation of PMS. The distinctive confined structure endowed MF-MnOx with a special pathway for the PMS activation. The direct oxidation of BPA on the intercalated MnOx induced the charge imbalance in the MnFe-LDH layer, resulting in the selective generation of 1O2. Moreover, acceptable activity deterioration of MF-MnOx was observed in a 10 h continuous degradation test in actual water, substantiating the application potential of MF-MnOx. This work presents a novel catalyst for the selective production of 1O2, and evaluates its prospects in the remediation of micro-polluted water.

Towards greener water remediation: Ca-impregnated pyro-hydrochar of spent mushroom substrate for enhanced adsorption of acridine red and methylene blue

Sustainable solutions for environmental remediation are of great interest due to the escalated release of toxic substances into the ecosystem. Here, Ca-impregnated pyro-hydrocarbon (Ca-SMS) was synthesized from spent mushroom substrate (SMS) via hydrothermal carbonization at a relatively low process temperature, followed by subsequent physicochemical activation. Ca-SMS underwent characterization using various analytical techniques, and its efficacy in removing acridine red (AR) and methylene blue (MB) was assessed through batch experiments. The results suggested that Ca-SMS is an effective adsorbent for AR and MB, visiting a removal capacity of 33.82 and 81.98 mg g−1 at 35 °C, respectively. The kinetic investigation uncovered that the dye removal process mostly agreed with the pseudo-second-order (PSO), while the Langmuir and Freundlich models were the most suitable to describe the removal of dyes. Thermodynamic analyses showed that the remediation process is spontaneous and endothermic. Adsorption mechanisms among dyes and Ca-SMS were multiple: physical adsorption, surface complexation, electrostatic, and π-π interaction. The feasibility of the proposed method for real sample treatment was demonstrated. These findings indicate that Ca-SMS is an effective alternative sorbent for the remediation of textile wastewater and is a viable solution for waste reduction in the rising mushroom cultivation sector.

Biodegradation of the strobilurin fungicide pyraclostrobin by Burkholderia sp. Pyr-1: Characteristics, degradation pathway, water remediation, and toxicity assessment

Pyraclostrobin, a widely used fungicide, poses significant risks to both the environment and human health. However, research on the microbial degradation process of pyraclostrobin was scarce. Here, a pyraclostrobin-degrading strain, identified as Burkholderia sp. Pyr-1, was isolated from activated sludge. Pyraclostrobin was efficiently degraded by strain Pyr-1, and completely eliminated within 6 d in the presence of glucose. Additionally, pyraclostrobin degradation was significantly enhanced by the addition of divalent metal cations (Mn2+ and Cu2+). The degradation pathway involving ether bond and N–O bond cleavage was proposed by metabolite identification. The sodium alginate-immobilized strain Pyr-1 had a higher pyraclostrobin removal rate from contaminated lake water than the free cells. Moreover, the toxicity evaluation demonstrated that the metabolite 1-(4-chlorophenyl)-1H-pyrazol-3-ol significantly more effectively inhibited Chlorella ellipsoidea than pyraclostrobin, while its degradation products by strain Pyr-1 alleviated the growth inhibition of C. ellipsoidea, which confirmed that the low-toxic metabolites were generated from pyraclostrobin by strain Pyr-1. The study provides a potential strain Pyr-1 for the bioremediation in pyraclostrobin-contaminated aquatic environments.

Synthesis of Fe-doped sludge biochar from Fenton sludge for efficient activation of peroxymonosulfate in tetracycline hydrochloride degradation

Traditional sludge treatment methods have problems in terms of environmental safety and cost-effectiveness. In this study, we followed the principle of "waste for waste" to synthesize magnetic sludge biochar (FSBC800) from biochemical sludge and Fenton sludge to activate persulfate (PMS) to remove persistent pollutants. Tetracycline hydrochloride (TC-HCl) was degraded up to 90.9% by FSBC800 using an active PMS system in just 30 minutes. This removal rate is higher than that of Fenton sludge biochar and biochemical sludge biochar by 2.7 and 1.8 times, respectively. The self-contained Fe in Fenton sludge formed evenly distributed Fe3O4 particles, while the biochemical sludge provided a large number of oxygen-containing functional groups, which increased the reactive active sites of FSBC800 and improved the catalytic performance. The dominant role of SO₄•⁻, •OH, and ¹O₂ in the degradation of TC-HCl was demonstrated by the identification of reactive oxygen species and electron paramagnetic resonance (EPR) analysis. By examining the intermediates, a potential TC-HCl degradation pathway was postulated. The catalyst has good reusability and practical application, and the removal of TC-HCl was still 84.8% after four replicated experiments. This study establishes a cost-effective, efficient, and recyclable biochar-based catalyst for water remediation, and at the same realizes resourceful utilization of sludge.

Effects of common dissolved anions on the efficiency of Fe0-based remediation systems

Quiescent batch experiments were conducted to evaluate the influences of Cl−, F−, HCO3−, HPO42−, and SO42− on the reactivity of metallic iron (Fe0) for water remediation using the methylene blue (MB) method. Strong discoloration of MB indicates high availability of solid iron corrosion products (FeCPs). Tap water was used as an operational reference. Experiments were carried out in graduated test tubes (22 mL) for up to 45 d, using 0.1 g of Fe0 and 0.5 g of sand. Operational parameters investigated were (i) equilibration time (0–45 d), (ii) 4 different types of Fe0, (iii) anion concentration (10 values), and (iv) use of MB and Orange II (O-II). The degree of dye discoloration, the pH, and the iron concentration were monitored in each system. Relative to the reference system, HCO3− enhanced the extent of MB discoloration, while Cl−, F−, HPO42−, and SO42− inhibited it. A different behavior was observed for O-II discoloration: in particular, HCO3− inhibited O-II discoloration. The increased MB discoloration in the HCO3− system was justified by considering the availability of FeCPs as contaminant scavengers, pH increase, and contact time. The addition of any other anion initially delays the availability of FeCPs. Conflicting results in the literature can be attributed to the use of inappropriate experimental conditions. The results indicate that the application of Fe0–based systems for water remediation is a highly site-specific issue which has to include the anion chemistry of the water.

Metagenomic Insight into the Effect of Probiotics on Nitrogen Cycle in the Coilia nasus Aquaculture Pond Water.

Recently, probiotics have been widely applied for the in situ remediation of aquatic water. Numerous studies have proved that probiotics can regulate water quality by improving the microbial community. Nitrogen cycling, induced by microorganisms, is a crucial process for maintaining the balance of the aquatic ecosystem. Nevertheless, the underlying mechanisms by which probiotics enhance water quality in aquatic systems remain poorly understood. To explore the water quality indicators and their correlation with nitrogen cycling-related functional genes, metagenomic analysis of element cycling was performed to identify nitrogen cycling-related functional genes in Coilia nasus aquatic water between the control group (C) and the groups supplemented with probiotics in feed (PF) or water (PW). The results showed that adding probiotics to the aquatic water could reduce the concentrations of ammonia nitrogen (NH4+-N), nitrite (NO2--N), and total nitrogen (TN) in the water. Community structure analysis revealed that the relative abundance of Verrucomicrobiota was increased from 30 d to 120 d (2.61% to 6.35%) in the PW group, while the relative abundance of Cyanobacteria was decreased from 30 d to 120 d (5.66% to 1.77%). We constructed a nitrogen cycling pathway diagram for C. nasus aquaculture ponds. The nitrogen cycle functional analysis showed that adding probiotics to the water could increase the relative abundance of the amoC_B and hao (Nitrification pathways) and the nirS and nosZ (Denitrification pathways). Correlation analysis revealed that NH4+-N was significantly negatively correlated with Limnohabitans, Sediminibacterium, and Algoriphagus, while NO2--N was significantly negatively correlated with Roseomonas and Rubrivivax. Our study demonstrated that adding probiotics to the water can promote nitrogen element conversion and migration, facilitate nitrogen cycling, benefit ecological environment protection, and remove nitrogen-containing compounds in aquaculture systems by altering the relative abundance of nitrogen cycling-related functional genes and microorganisms.

A S-scheme heterojunction of MIL-125(Ti)/BiOBr for remediation of organic and inorganic pollutants coexistent real water: Application and mechanism investigation

The remediation of real wastewater consistently garners significant attention; however, the complexity of treating substrates due to the coexistence of organic and inorganic pollutants often renders treatment challenging. In response to this issue, a visible-light-driven photocatalyst, MIL-125(Ti)/BiOBr, was meticulously designed and synthesized. This catalyst was employed to statically treat tetracycline and Cr(VI) individually across three distinct treatment models: adsorption, photocatalysis, and the synergistic combination of adsorption-photocatalysis. Through this exploration, it was determined that the adsorption-photocatalysis synergism emerged as the optimal treatment model. The MIL-125(Ti)/BiOBr system exhibited outstanding tetracycline degradation performance (100% of tetracycline can be removed after 40 min and 100% of Cr(VI) can be removed after 45 min). Then, MIL-125(Ti)/BiOBr was applied to treat tetracycline and Cr(VI) individually or simultaneously under adsorption-photocatalysis model, to confirm tetracycline and Cr(VI) didn’t interfere each other. At last, to evaluate the practical application of MIL-125(Ti)/BiOBr, it was utilized to treat three real water bodies simultaneously containing tetracycline and Cr(VI) in continuous flowing manner. The results highlight the remarkable capability of MIL-125(Ti)/BiOBr in treating wastewater containing both organic and inorganic pollutants. Mechanistic analysis revealed the establishment of an efficient S-scheme charge-carrier transfer pathway at the interface of MIL-125(Ti) and BiOBr, effectively suppressing charge carrier recombination and thereby enhancing photocatalytic performance. This study offers a novel perspective on the construction of bifunctional photocatalysts, which hold promise in addressing the challenge of intractable wastewater treatment in real-world scenarios.

Synergistic RB5 dye degradation and oxygen evolution reaction (OER) catalysis by WO3 nano-pellets: mechanistic insights and water remediation applications

Transition metal oxides (TMO), a non-noble element based oxides, establish remarkable potential in the realm of textile wastewater remediation and water splitting due to their sustainable catalytic performance. Highly functional TMO materials, in form of nanostrcutures, are of great interest owing to their robust photo and electro-catalytic activities for instituting sustainable development for the water and energy resource management framework. In the present article, we have reported catalytically active WO3 nano-pellets (NP) synthesized using microwave-assisted for photocatalytic wastewater remediation and electrocatalytic oxygen evolution reaction (OER). Promisingly, WO3 NP abetted degradation of the reactive black 5 (RB5) dye by almost 95 % in short time interval of 60 min in exposer of sun light. Present work includes the strategies to remove and observe the progression of reaction kinetics of dye degradation in neutral and alkaline media. By varying concentration of the catalyst (ranging from 250 mg/L to 1000 mg/L, in the step of 250 mg/L), we have prolifically verified that 750 mg/L turn out optimal dosage for 100% degradation in time interval of 120 min. Besides, WO3 NP has shown highest photocatalytic behaviour at 9 pH. The WO3 NP shows the electrocatalytic OER performance in an alkaline condition (1M KOH) with an overpotential of 418 mV to generate the geometric current density of 10 mA/cm² and Tafel slope of 178 mV dec⁻¹. Owing to robust nature, WO3 NP shows the almost similar photocatalytic response for ten cycles dye degradation and demonstrates the stable electrochemical charge transport for OER at 10 mA/cm2 for 50 hours.

Photocatalytic Degradation of Tetracycline Hydrochloride Based on the Structure-Property Exploration of BiOCl.

The correlation between structure and properties in the photodegradation reaction of bismuth oxychloride (BiOCl) was explored in this work. Three BiOCl samples with different sizes, morphological structures, and defects were prepared through a hydrothermal method with experimental manipulation. Their structural properties were comprehensively characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electron spin resonance, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, and photoluminescence. Taking the photodegradation of tetracycline hydrochloride (TC-HCl) as the probe reaction, we found that high activity could be achieved by decreasing their crystal size and thickness, introducing proper defects in the structure, and assembling the nanosheets to get microball structure. Combined with radical-scavenge experiments and electron spin resonance (ESR) spin-trap spectra, we conclude that ̇O2- was the dominant reactive oxygen species for the degradation reaction. The degradation detailed pathway of TC-HCl was further analyzed using liquid chromatography-mass spectrometry. This work explores the structure-property correlation of BiOCl and provides strategies for the rational design of active photocatalysts for water remediation.

Superoxide versus peroxide activation of dye decolorizing peroxidases for bioelectrocatalysis

Here we show that dye decolorizing peroxidases can be electrochemically activated for substrate oxidation without addition of exogenous H2O2, yielding activities similar or better than in their conventional operation. The method is based on the in situ generation of O2•−, •OH and H2O2. These species bind the heme to form catalytically competent oxoiron intermediates. Activation of the Pseudomonas putida enzyme is mainly mediated by O2•−, while those from Thermobifida fusca and Saccharomonospora viridis show preferential activation by H2O2. This differential reactivity is explained by the dynamics of a conserved distal aspartate residue. In contrast to previous reports on the Bacillus subtilis enzyme, none of the peroxidases studied here show significant •OH mediated activation, as this radical is quenched by reactive amino acids abundant in these proteins. These results pave the way for the development of bioelectrocatalytic reactors based on dye decolorizing peroxidases for water remediation and biomass processing.

Chitosan/magnetic biochar composite with enhanced reusability: Synergistic effect of functional groups and multilayer structure

Heavy metals in water bodies pose a significant threat to both ecology and human well-being. Therefore, the development of green and sustainable adsorbents for water remediation is essential. This study presents a crosslinked chitosan composite structure with multiple layers, which was generated by adjusting the ratio of chitosan to wheat straw–derived magnetic biochar in the composite. The adsorption behavior of the composite under different conditions was revealed by varying the Cr(VI) concentration, pH, and temperature. The composite exhibited a maximum adsorption of 121.8 mg g−1 for Cr(VI) in water, which was 11.9 times higher than that of magnetic biochar. It maintained a residual performance of 78.6 % after seven cycles, higher than most chitosan-based composites. The reusability was improved via hydrochloric acid protonation of functional groups and layer-by-layer exposure of the composite structure. This study provides new insights into the application of composites derived from chitosan and wheat straw, an agricultural waste, as sustainable adsorbents.