Remediation Of Organic Contaminants Research Articles

Eco-friendly biomass aerogels from moxibustion waste for sustainable remediation of organic contaminants

Powder adsorbents present limited recyclability when used for wastewater treatment. Bulk materials prepared via eco-friendly approaches typically exhibit excellent reproducibility over powders in terms of removing pollutants from aquatic environments. Here, biomass-based aerogels were synthesized via ball milling a mixture of modified moxa ash (a type of moxibustion waste), carbon nanotubes and ammonia, combined with agarose as biomolecule. The obtained aerogels display low density, high porosity, remarkable mechanical properties, and exceptional repeatability and stability for removing organic pollutants. By employing a two-dimensional (2D) aerogel membrane, pollutants such as 10 mg/L mitoxantrone (MTX), 5 mg/L methylene blue, 5 mg/L malachite green, or 5 mg/L rhodamine B could be dynamically adsorbed and swiftly filtered out, achieving nearly 100 % of the removal rate. For three-dimensional (3D) aerogels, efficient removals of MTX (98.4 % at 135 min) and cationic dyes under various conditions were observed, in which the adsorption capacity reached 28.23 mg/g for low concentration of MTX at 120 min. After four cycles, the aerogel still retained 93 % of its original capacity and the removal rate was still 92.4 %. The adsorption process obeys second-order kinetics and adheres to the Freundlich and Temkin isotherm models. Furthermore, the primary mechanism by which the aerogels adsorb MTX includes pore filling, electrostatic interactions, π-π conjugation and hydrogen bonding. The adsorption mechanism was better explained by the results of density functional theory. Biomass-based 2D/3D aerogels are promising, low-cost, eco-friendly and highly efficient absorbents for mitigating wastewater contamination.

Preparation of Cobalt-Nitrogen Co-Doped Carbon Nanotubes for Activated Peroxymonosulfate Degradation of Carbamazepine.

Cobalt-nitrogen co-doped carbon nanotubes (Co3@NCNT-800) were synthesized via a facile and economical approach to investigate the efficient degradation of organic pollutants in aqueous environments. This material demonstrated high catalytic efficiency in the degradation of carbamazepine (CBZ) in the presence of peroxymonosulfate (PMS). The experimental data revealed that at a neutral pH of 7 and an initial CBZ concentration of 20 mg/L, the application of Co3@NCNT-800 at 0.2 g/L facilitated a degradation rate of 64.7% within 60 min. Mechanistic investigations indicated that the presence of pyridinic nitrogen and cobalt species enhanced the generation of reactive oxygen species. Radical scavenging assays and electron spin resonance spectroscopy confirmed that radical and nonradical pathways contributed to CBZ degradation, with the nonradical mechanism being predominant. This research presents the development of a novel PMS catalyst, synthesized through an efficient and stable method, which provides a cost-effective solution for the remediation of organic contaminants in water.

Active and stable Co[sbnd]Ox sites promote peroxymonosulfate activation for sulfamethoxazole degradation through nonradical pathways

Cobalt (Co) single-atom sites are considered as the most efficient active sites in peroxymonosulfate (PMS) based advanced oxidation processes. However, CoO configurations instead of Co-N configurations were scarcely explored. Herein, isolated Co single atoms were successfully implanted onto hydroxyl decorated UiO-66 (Co/UiO-66-220) to generate [Zr6O4(OH)4(BDC)5.35(OH)1.30(OH2)1.30] structure to form {ZrOCoOZr} single-site through coordination strategy. Owing to the strong electron transfer ability of CoOx sites, the Co/UiO-66-220/PMS system displayed outstanding degradation performance and 100 % sulfamethoxazole (SMX) degradation efficiency was achieved within 10 min. Remarkably, the system also displayed excellent degradation performance in the presence of anions and complex actual wastewater. The membrane system was particularly effective, achieving a 90.32 % removal efficiency within 240 min. The nonradical species, singlet oxygen (52.8 %), electron transfer (4.9 %) and high-valent cobalt-oxo species (Co (IV) = O) (23.9 %), were dominated in the degradation process. The generated intermediates are low-toxicity. The results demonstrate the excellent activity of CoOx sites for PMS activation and its practical application potential for remediation of organic contaminants.

Fabrication of porous beta-cyclodextrin functionalized PVDF/Fe–MOF mixed matrix membrane for enhanced ciprofloxacin removal

Herein, we demonstrate the synthesis of beta-cyclodextrin (β–CD) functionalized polyvinylidene fluoride (PVDF) and iron-based metal-organic framework (Fe–MOF) mixed matrix membrane (MMM) for the enhanced removal of ciprofloxacin (CIP) from water. The membranes were prepared using the phase inversion technique with PVDF as the polymer matrix, Fe–MOF as the filler, and polyvinylpyrrolidone (PVP) as the porogen. The optimized MMM with 7% wt. Fe–MOF exhibited excellent performance with 87.6% removal efficiency. Moreover, the maximum adsorption capacity was 6.43 mg g–1. The β–CD functionalization improved the MMM hydrophilicity exhibited by the water contact angle (WCA) analysis (WCA = 55°). Furthermore, excellent adsorption performance can be attributed to the large Fe–MOF specific surface area (682.5 m2 g–1), the high porosity (77%), and the average pore diameter (395 nm) of the membrane. The inclusion of PVP (1% wt.) enhanced the porous nature of the MMM and, consequently, the adsorption performance for CIP. Notably, the hydrophilic and macroporous membrane showed good reusability with over 70% removal efficiency after five sequential adsorption–desorption cycles. The insights from this study suggest that the PMC–7 membrane can be an excellent candidate for the remediation of organic contaminants from aquatic environments.

Mn3O4/Vulcan XC-72R composites: preparation, physicochemical characterization and electrochemical study for purification of organic contaminants

The microwave-assisted technique was applied to the preparation of composites from manganese(II) acetate and Carbon-supported (Vulcan XC-72R). Composites were prepared by chemical deposition of manganese(II) acetate nanoparticles onto Vulcan XC-72R carbon black (catalytic mass) using microwave irradiation. The new composites were physicochemically characterized by Energy-dispersive X-ray spectroscopy (EDX) with scanning electron microscopy (SEM), BET surface area, pore size distribution and X-ray diffraction (XRD). BET analysis of Mn3O4/Vulcan XC-72R composites obtained by alkali method has shown specific surface area of 1135 m2/g. Novel composites were electrochemically studied as catalysts for the remediation of organic contaminants in industrial waters. From novel catalytic mass, double-sided coated electrodes on a Nickel mesh conductor were made by pressing and heating at 250 °C. The prepared electrodes have geometric area of 2.5 cm2. The electrodes were fabricated and studied regarding the amount of catalyst and 35 % Teflonized Vulcan XC-72R. Electrochemical studies were carried out for phenol oxidation in an aqueous solution in model electrolyte: phenol solution 200 mg.L-1 and supporting electrolyte: 18 g.L-1 NaCl and 2.6 mg.L-1 Na2SO4.

Enhanced peroxymonosulfate (PMS) activation process mediated by vanadium modified CoO catalyst for rapid degradation of organic pollutants: Insights into the role of V

Developing the transition metal catalysts with high reactivity for the sulfate radical (SO4－·) based advanced oxidation processes (SR-AOPs) has been attracting numerous attentions. To improve the peroxymonosulfate (PMS) activation process mediated by Co-based catalysts, a vanadium-cobalt bimetallic catalyst (V@CoO) was fabricated by modification vanadium through a simple solvothermal method. The pollutants degradation experiments showed that the obtained V@CoO exhibited much higher performance on PMS activation (5.55–8.33 times larger of apparent rate constants) than pure CoO, and the V@CoO/PMS system could quickly degrade various organic contaminants within 5 min under the attack of both radicals (SO4－·and O2－·) and non-radicals (1O2). The density functional theory (DFT) calculations and electrochemical tests revealed that the enhancing mechanism of V modification involved four aspects: (i) promoting the PMS adsorption on the surface of V@CoO; (ii) enhancing the electron transfer efficiency between V@CoO and PMS; (iii) activating PMS with V3+ and V4+ species; (iv) accelerating the circulation of Co2+ and Co3+, leading to the promotion on the production of reactive oxygen species (ROS). Furthermore, the V@CoO/PMS system also exhibited satisfactory stability in a broad pH range and good efficiency in the presence of co-existing components (HCO3−, NO3−, PO43−, Cl− and HA) in water. This study will provide new insights to designing high-performance, environment-friendly bimetal catalysts and some basis for the remediation of organic contaminants with SR-AOPs.

Tailoring photocatalytic performance through Fe-doped TiO2/ZnO for effective remediation of organic contaminants

The development of highly efficient photocatalysts holds significant promise for addressing contemporary environmental challenges. This study focuses on the synthesis and characterization of a novel photocatalyst, iron-doped TiO2/ZnO particles, created through the sol-gel technique. The incorporation of iron ions into the crystalline structure of TiO2/ZnO aims to enhance the photocatalytic efficiency of TiO2. The findings revealed that Fe–ZnO/TiO2 exhibits a more thermally stable lattice compared to TiO2/ZnO, thereby retarding the phase transformation from anatase to rutile under higher calcination temperature. The photocatalytic performance of the synthesized photocatalyst was evaluated through the degradation of methyl orange under visible light irradiation. A statistical response surface methodology based on a central composite design was employed to develop a predictive model for color removal (as the dependent variable) considering variations in irradiation intensity, initial color concentration, catalyst concentration, reaction time, and pH (as independent variables). The analysis of variance identified the initial color concentration as the most influential factor, negatively affecting the predicted response. The experimental values of color removal exhibited good agreement with the predicted values from the regression model with a coefficient of determination of 0.949, indicating the accuracy of this model in predicting the mentioned outcomes. The presented model indicated that, for a sample of methyl orange with an initial concentration of 21.97 ppm, a reaction time of 117.69 min under direct irradiation of 21.63 W, a catalyst concentration of 0.61 g/L, and a pH of 4.74, the optimal color removal efficiency of 78.99 % was achieved.

Photocatalytic and adsorption behavior of a new efficient LaxNiyMn3–(x+y)O4/SiO2 composite for environmental remediation application

Environmental remediation of organic contaminants has recently received significant attention, necessitating the development of energy-efficient, cost effective, and environment-friendly catalysts. In this study, novel dual-doped LaxNiyMn3–(x+y)O4 nanoparticles (NPs) and their composite with an adsorptive material (mesoporous silica) were synthesized using a low-cost, environment-friendly coprecipitation technique. The as-prepared LaxNiyMn3–(x+y)O4 NPs and their composite were studied via X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), Fourier-transform infrared (FTIR) spectroscopy, and ultraviolet–visible spectroscopy. XRD analysis revealed that the LaxNiyMn3–(x+y)O4 NPs possessed a crystalline structure. FESEM showed that LaxNiyMn3–(x+y)O4 NPs were spherical with diameters ranging from 60 to 100 nm. The presence of metal–oxygen bonds in the LaxNiyMn3–(x+y)O4 NPs was confirmed by FTIR analysis. The LaxNiyMn3–(x+y)O4 NPs could degrade crystal violet (CV) dye under visible light with a percentage degradation of 82%, which increased to 92% with the addition of 0.5 mL of 6% H2O2 solution. Furthermore, to increase the adsorption ability of the LaxNiyMn3–(x+y)O4 NPs, a composite LaxNiyMn3–(x+y)O4/SiO2 was synthesized. Under dark conditions, the adsorption percentage of the LaxNiyMn3–(x+y)O4 NPs was 58%, whereas that of LaxNiyMn3–(x+y)O4/SiO2 reached 73%. The adsorption process was further explored using adsorption isotherms and reaction kinetic models. The central composite rotatable design of response surface methodology was used to statistically maximize the adsorption of CV by optimizing factors such as time (40 min), pH (8.68), and composite dose (12 mg). The prominent diffraction peak in the XRD pattern and the large surface area (532 m2/g) determined via Brunauer–Emmett–Teller analysis of the composite confirmed its unique porous characteristics, illustrating its high capacity for adsorbing pollutants inside the porous network. Studies on the degradation efficiency and adsorption–photocatalysis synergy suggest the substantial potential of the synthesized composite for application in environmental remediation.

Assessment of g‒Mg3N2 membrane performance for efficient removal of dioxane contaminant from wastewater: DFT‒MD simulation treatments

We implemented DFT calculations for gas phase and DFT‒MD simulations for ambient conditions to evaluate the efficient performance of g‒Mg3N2 monolayer in 1,4‒dioxane removal from wastewater. The geometries, interaction energies, and interaction nature of the adsorbed dioxane and H2O molecules on the Mg3N2 surface were investigated. It was found that the interaction of H2O exceeds that of dioxane by twelve though, the two adsorbates follow rather a similar trend in the adsorption process. The AIM analysis was carried out to investigate the nature of bonding for adsorbed dioxane/H2O on the Mg3N2 surface. Furthermore, DFT‒MD simulation shows that dioxane tends to adsorb on the Mg3N2 nanosheet in the presence of water molecules at ambient conditions, making the Mg3N2 potentially suitable adsorbent for dioxane adsorption in aqueous solution. This exploration presents a foundation for the capability of computational study for predicting the adsorption and remediation of organic contaminants from wastewater.

An Up-to-Date Review on the Remediation of Dyes and Phenolic Compounds from Wastewaters Using Enzymes Immobilized on Emerging and Nanostructured Materials: Promises and Challenges.

Addressing the critical issue of water pollution, this review article emphasizes the need to remove hazardous dyes and phenolic compounds from wastewater. These pollutants pose severe risks due to their toxic, mutagenic, and carcinogenic properties. The study explores various techniques for the remediation of organic contaminants from wastewater, including an enzymatic approach. A significant challenge in enzymatic wastewater treatment is the loss of enzyme activity and difficulty in recovery post-treatment. To mitigate these issues, this review examines the strategy of immobilizing enzymes on newly developed nanostructured materials like graphene, carbon nanotubes (CNTs), and metal-organic frameworks (MOFs). These materials offer high surface areas, excellent porosity, and ample anchoring sites for effective enzyme immobilization. The review evaluates recent research on enzyme immobilization on these supports and their applications in biocatalytic nanoparticles. It also analyzes the impact of operational factors (e.g., time, pH, and temperature) on dye and phenolic compound removal from wastewater using these enzymes. Despite promising outcomes, this review acknowledges the challenges for large-scale implementation and offers recommendations for future research to tackle these obstacles. This review concludes by suggesting that enzyme immobilization on these emerging materials could present a sustainable, environmentally friendly solution to the escalating water pollution crisis.

Self-formed MnCO3/FeS2@SiO2 in modified electrolytic manganese residues as an enhanced peroxymonosulfate activator for ammonium dibutyl dithiophosphate removal

In this study, a peroxymonosulfate (PMS) activator named NMN95 using electrolytic manganese residues (EMR) as raw material was successfully synthesized. The NMN95 consisting of MnCO3, FeS2 and SiO2 showed excellent degradation ability for ammonium dibutyl dithiophosphate (ADD) attributed to the synergistic effects of Fe, Mn and reducing S species. Under the optimum conditions, the NMN95/PMS system could effectively degrade 95.8% of ADD (100 mg/L) within 30 min. The degradation system could produce a large number of free radicals including sulfate radical (SO4•−), hydroxyl radical (•OH) and superoxide radical (O2•−), as well as the non-radical singlet oxygen (1O2), in which O2•− and 1O2 played the crucial role in decomposing the ADD molecule. Spectroscopic analysis and density functional theory (DFT) demonstrated that the adsorption and activation of PMS are more favorable on MnCO3 than FeS2, where S sites in FeS2 acted as the electron donor to accelerate the transformation between high and low valance of Mn and Fe. Additionally, P1, S2, S5 and N14 on ADD molecules were in sensitive positions attacked by reactive species. Cyclic and metal ions leaching experiments showed that NMN95 has excellent reusability and stability within seven cycles. This study has sought a new high-value utilization approach for EMR and provided an efficient degradation system for the remediation of organic contaminants in beneficiation wastewater.

Electrospun TiO2-GO/PAN-CA nanofiber mats: A novel material for remediation of organic contaminants and nitrophenol reduction

The outstanding properties of nanofiber composites have made them a popular choice for various structural applications. Recently, there has been a growing interest in using electrospun nanofibers as reinforcement agents, which possess exceptional properties that can enhance the performance of these composites. Herein, TiO2-graphene oxide (GO) nanocomposite incorporated into polyacrylonitrile (PAN)/cellulose acetate (CA) nanofibers were fabricated by an effortless electrospinning technique. The chemical and structural characteristics of the resulting electrospun TiO2-GO nanofibers were examined employing diverse techniques such as XRD, FTIR, XPS, TGA, mechanical properties, and FESEM. Remediation of organic contaminants and organic transformation reactions with electrospun TiO2-GO nanofibers were performed. The results indicated that the incorporation of TiO2-GO with various TiO2/GO ratios did not affect the molecular structure of PAN-CA. Still, they did significantly increase the mean fiber diameter (234–467 nm) and the mechanical properties of the nanofibers comprising UTS, elongation, Young's modulus, and toughness compared to PAN-CA. From various ratios of TiO2/GO (0.01TiO2/0.005GO and 0.005TiO2/0.01GO) in the electrospun NFs, the nanofiber containing a high content of TiO2 showed over 97% of the initial MB dyes were degraded after 120 min of visible light exposure and the same nanofibers also, achieved 96% nitrophenol conversion to aminophenol in just 10 min with activity factor kAF value of 47.7 g−1min−1. These findings illustrate the promise of TiO2-GO/PAN-CA nanofibers for use in various structural applications, particularly in the remediation of organic contaminants from water and organic transformation reactions.

Efficient degradation of norfloxacin using a novel biochar-supported CuO/Fe3O4 combined with peroxydisulfate: Insights into enhanced contribution of nonradical pathway

Nonradical persulfate oxidation techniques have evolved as a new contaminated water treatment approach due to its great tolerance to water matrixes. The catalysts of CuO-based composites have received much attention in that aside from SO4•−/•OH radicals, the nonradicals of singlet oxygen (1O2) can be also generated during persulfate activation via CuO. However, the issues regarding particles aggregation and metal leaching from the catalysts during the decontamination process remain to be addressed, which could have a remarkable impact on the catalytic degradation of organic pollutants. Accordingly in the present study, a novel biochar-supported bimetallic Fe3O4–CuO catalyst (CuFeBC) was facilely developed to activate peroxodisulfate (PDS) for the degradation of norfloxacin (NOR) in aqueous solution. The results showed CuFeBC has a superior stability against metal ions Cu/Fe leaching, and NOR (30 mg L−1) was degraded at 94.5% within 180 min in the presence of CuFeBC (0.5 g L−1) and PDS (6 mM) in pH 8.5. The scavenging of reactive oxygen species and electron spin resonance analysis revealed that 1O2 dominated the degradation of NOR. Compared with pristine CuO–Fe3O4, the interaction between biochar substrate and metal particles could significantly enhance the contribution of the nonradical pathway to NOR degradation from 49.6% to 84.7%. Biochar substrate could efficiently reduce the leaching of metal species from the catalyst, thereby maintaining excellent catalytic activity and lasting reusability of the catalyst. These findings could enlighten new insights into fine-tuning radical/nonradical processes from CuO-based catalysts for the efficient remediation of organic contaminants in polluted water.

Non-reactive facet specific adsorption as a route to remediation of chlorinated organic contaminants

The present work quantifies metal-contaminant interactions between palladium substrates and three salient chlorinated organic contaminants, namely trichloroethylene 1,3,5-trichlorobenzene (TCB), and 3,3′,4,4′-tetrachlorobiphenyl (PCB77). Given that Pd is one of the conventional catalytically active materials known for contaminant removal, maximizing catalytic efficiency through optimal adsorption dynamics reduces the cost of remediation of contaminants that are persistent water pollutants chronically affecting public health. Adsorption efficiency analyses from all-atom molecular dynamics (MD) simulations advance the understanding of reaction mechanisms available from density functional theory (DFT) calculations to an extractable feature scale that can fit the parametric design of supported metal catalytic systems and feed into high throughput catalyst selection. Data on residence time, site-specific adsorption, binding energies, packing geometries, orientation profiles, and the effect of adsorbate size show the anomalous behaviour of organic contaminant adsorption on the undercoordinated {110} surface as compared to the {111} and {100} surfaces. The intermolecular interaction within contaminants from molecular dynamics simulation exhibits refreshing results than ordinary single molecule density functional theory calculation. Since complete adsorption and dechlorination is an essential step for chlorinated organic contaminant remediation pathways, the presented profiles provide essential information for designing efficient remediation systems through facet-controlled palladium nanoparticles.

New insight into the activation mechanism of hydrogen peroxide by greigite (Fe3S4) for benzene removal: The combined action of dissolved and surface bounded ferrous iron

Iron sulfides have attracted growing concern in heterogeneous Fenton reaction. However, the structure of iron sulfides is different from that of iron oxides and how the structures affect the activation property of hydrogen peroxide (H2O2) remains unclear. This study investigated benzene removal through the activation of H2O2 by the synthesized magnetite (Fe3O4) and greigite (Fe3S4). The structures of Fe3O4 and Fe3S4 were characterized by XRD and EPR, the electron transfer properties of Fe3O4 and Fe3S4 were analyzed by electrochemical workstation, XPS and DFT. It is revealed that the effective benzene removal rate of 88.86％ in the Fe3S4/H2O2 was achieved, which compared to 15.58％ obtainable from the Fe3O4/H2O2, with the apparent rate constant in the Fe3S4/H2O2 being approximately 65 times over that in the Fe3O4/H2O2. The better H2O2 activation by Fe3S4 was attributed to the significant roles of S (-II) and S vacancies in regulating the dissolution of ferrous iron ions, thus generating abundant free •OH radical. In addition, surface bounded ferrous iron of Fe3S4 could transfer more electrons to H2O2 and O2 to generate more surface bounded •OH and •O2−. This study revealed the combined action of dissolved and surface bounded ferrous iron of greigite on H2O2 activation, and provides an efficient heterogeneous H2O2 activator for the remediation of organic contaminants in groundwater.

Regulating energy band structures of triazine covalent organic frameworks with electron-donating/withdrawing substituents for visible-light-responsive photocatalytic tetracycline degradation and Cr(VI) reduction

Environmental contaminations have raised soaring concerns about human health worldwide. Developing metal-free photocatalysts as green agents to solve these problems is urgent. Covalent organic frameworks (COFs) are considered a promising platform for the molecule-level design of visible-light-responsive photocatalysts due to their tailored coordination/electronic structures and excellent charge carrier mobility. However, COFs without substituents (e.g., COFs-H) still suffer from broad bandgaps and low electron-hole separation efficiency. In this work, we introduced electron-donating/withdrawing substituents on COFs-H to fine-tune the bandgap and photocatalytic performance of COFs. Theoretical and experimental studies revealed that all substituents narrowed the bandgap of COFs and enhanced the electron-hole separation efficiency. Electron-withdrawing/donating substituents significantly alter the energy level of COFs-R, improving the redox capacities of photo-generated holes and electrons for tetracycline (TC) degradation and Cr(VI) reduction. The large difference in electrostatic potential between the two monomers in COFs-R enhances the charge carrier generation and intramolecular electron transfer intrinsically. This work unravels how substituents with different electronic effects regulate the energy band structures and photo-redox capacities of COFs. It further provides new insight into the precise regulation of COFs toward highly efficient visible-light-driven photocatalytic remediation of organic contaminants and heavy metal ions.

A Review on Wastewater Treatment Containing Organic Pollutants Using Advance Oxidation Processes

Advanced oxidation processes (AOPs) are the technologies that generally use the hydroxyl radicals, the ultimate oxidant for the remediation of organic contaminants in wastewater. These are highly effective novel methods speeding up the oxidation process. AOPs can combine with Fenton (H2O2/Fe2+), photo-Fenton (H2O2/UV/Fe2+), and electro-Fenton, heterogeneous photooxidation using titanium dioxide (TiO2/hv), singlet molecular oxygen process, singlet oxygen-photo-Fenton process, sonolysis, peroxidation combined with ultraviolet light (H2O2/UV), UV alone, UV/O3, UV/S2O8-2, UV/Chlorine, peroxone (O3/H2O2), peroxone combined with ultraviolet light (O3/H2O2/UV), O3/UV system, O3/TiO2/ H2O2 and O3/TiO2/Electron beam irradiation. Ozone (O3), catalyst or ultraviolet (UV) irradiation to offer a powerful treatment processes of wastewater. Future research should be focused on enhancing the properties of heterogeneous catalysts in AOPs. This review report of different AOPs utilized for the removal of various phenolic compounds and textile dyes in wastewater.

A novel thermosensitive persulfate controlled-release hydrogel based on agarose/silica composite for sustained nitrobenzene degradation from groundwater

The increasing risk of organic contamination of groundwater poses a serious threat to the environment and human health, causing an urgent need to develop long-lasting and adaptable remediation materials. Controlled-release materials (CRMs) are capable of encapsulating oxidants to achieve long-lasting release properties in aquifers and considered to be effective strategies in groundwater remediation. In this study, novel hydrogels (ASGs) with thermosensitive properties were prepared based on agarose and silica to achieve controlled persulfate (PS) release. By adjusting the composition ratio, the gelation time and internal pore structure of the hydrogels were regulated for groundwater application, which in turn affected the PS encapsulated amount and release properties. The hydrogels exhibited significant temperature responsiveness, with 6.8 times faster gelation rates and 2.8 times longer controlled release ability at 10 ℃ than at 30 ℃. The ASGs were further combined with zero-valent iron to achieve long-lasting degradation of the typical nitrobenzene compound 2,4-dinitrotoluene (2,4-DNT), and the degradation performance was maintained at 50 % within 14 PV, which was significantly improved compared with that of the PS/ZVI system. This study provided new concepts for the design of controlled-release materials and theoretical support for the remediation of organic contamination.

Efficient activation of peroxymonosulfate via Cu2+/Cu+ cycle enhanced by hydroxylamine for the degradation of Rhodamine B.

The application of Cu2+/peroxymonosulfate (PMS) process for the elimination of refractory pollutants in industrial wastewater is limited by the slow transformation from Cu2+ to Cu+. In this research, hydroxylamine (HA) was employed to improve the degradation capacity of the Cu2+/PMS process. Rhodamine B (RhB) was selected as the target compound to indicate the performance of HA/Cu2+/PMS process. Compared with the Cu2+/PMS process, the reduction of Cu2+ to Cu+ was effectively promoted by HA in the HA/Cu2+/PMS process, which increased the decomposition rate of PMS by 29.2%, correspondingly, promoted the removal rate of RhB by 77.6%. The degradation of RhB followed pseudo-second-order kinetics in the proposed process. The active species analysis subsequently indicated hydroxyl radicals (·OH) and sulfate radicals (SO4·-) played important roles for degrading RhB with ·OH as the dominant active radical. The effects including initial pH, RhB concentration, PMS concentration, and Cu2+ concentration on the degradation of RhB were further investigated and discussed in detail. Additionally, the HA/Cu2+/PMS process exhibited effective RhB removal in simulated wastewater. From the perspective of waste utilization (Cu2+) and the remediation of organic contamination, the work would provide a valuable and promising process.

Cometabolic decomposition of trichloroethylene by recombinant hydroxyquinol 1,2-dioxygenase

Trichloroethylene (TCE) is known to microbially decomposed by a cometabolic process. In this study, a dioxygenase for the ring cleavage of benzenetriols was used to catalyze the cometabolic oxidation of TCE. Hydroxyquinol 1,2-dioxygenase (HQD) was obtained in vitro using a recombinant technique, and its catalytic function and products in the TCE cometabolic transformation were identified. The HQD (CphA-I) was cloned from Pseudarthrobacter chlorophenolicus A6, overexpressed, and purified using Ni2+-nitrilotriacetic acid (Ni2+-NTA) affinity chromatography, and soluble form of enzymes with 34 kDa protein size were effectively achieved with a high expression rate (4,177 μg/mL). TCE was effectively decomposed by CphA-I, and the specific activity was 5.1 U/mg-protein. The Hill equation was found to describe well the kinetics of TCE decomposition by CphA-I, which were determined as: vmax = 1.06 mM/min, KM = 1.44 mM, and nH = 2.41. This indicates that CphA-I has at least three cooperative binding sites for TCE decomposition, further accentuating the high affinity between the enzyme and the substrate. Glyoxylate and chloral hydrate were identified as the primary decomposition products from TCE cometabolic oxidation. This suggested that CphA-I exhibited a cometabolism catalytic function similar to those of methane monooxygenase and toluene dioxygenase. These results are expected to provide fundamental information for the enzymatic remediation of organic contaminants.