Removal Of Organic Pollutants Research Articles

Co-Ti Bimetallic Complex-Induced Phase Modulation of Co@Black TiO2 for Catalytic Hydrogenation of Cinnamaldehyde.

Transition-metal-doped black titania, primarily in the anatase phase, shows promise for redox reactions, water splitting, hydrogen generation, and organic pollutant removal, but exploring other titania phases for broader catalytic applications is underexplored. This study introduces a synthetic approach using a Co-Ti bimetallic complex bridged by a 1,10-phenanthroline-5,6-dione ligand as a precursor for the synthesis of cobalt-doped black titania [Co@L2N@b-TiO2]. The synthesis involves precise control of pyrolysis conditions, yielding a distinct structure dominated by the rutile phase over anatase, with active cobalt encapsulated within a nitrogen-doped graphitic layer, primarily as Co0 rather than CoII and CoIII. The synthesized material is employed for the selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) under industrially viable conditions. The efficiency and selectivity of Co@L2N@b-TiO2 was compared with other catalysts, including cobalt-doped rutile TiO2 (Co@r-TiO2), anatase TiO2 (Co@a-TiO2), and black titania (Co@b-TiO2) as well as materials pyrolyzed under different atmospheres and temperatures, materials with phenanthroline ligands, and materials lacking any ligands. The superior performance of Co@L2N@b-TiO2 is attributed to its high surface area, stable Co0 within the nitrogen-doped graphitic layer, and composition of rutile and anatase phases of TiO2 and Ti2O3 (referred to as RAT), along with the synergistic interaction between RAT and Co0. These factors significantly influence the efficiency and selectivity of COL over hydrocinnamaldehyde (HCAL) and hydrocinnamyl alcohol (HCOL), indicating potential for broader applications beyond catalysis, particularly in designing of black titania-based materials.

Development of a novel polydopamine-imprinted MOFs targeted for removal of refractory organic pollutants: Synergistic mechanisms of adsorption and degradation

In this study, a novel dopamine-imprinted MOFs (metal organic frameworks) was developed for the first time to achieve targeted degradation of refractory organic pollutants (ROPs) in advanced oxidation process. The targeted adsorption and degradation capacity of sulfamethoxazole (SMX) by molecularly imprinted catalyst (Fe-MOFs@MIP) was 3.17 times and 5.47 times that of Fe-MOFs, respectively. The results showed that the polydopamine (PDA) imprinted layer not only enhanced the targeted adsorption of SMX, but also improved the activity of the catalyst by promoting electron transfer. The physicochemical properties of Fe-MOFs@MIP were investigated. In situ Fourier transform infrared spectroscopy and molecular dynamics theory were used to investigate targeted adsorption mechanism. The active species were identified by quenching experiments and electron paramagnetic resonance (EPR). The reaction sites of SMX were predicted using density functional theory (DFT) and the possible degradation pathways of SMX were proposed. Finally, the targeted degradation mechanism of Fe-MOFs@MIP was elucidated. This study has a guiding significance for the deep removal of refractory organic pollutants in wastewater.

Determination of soil phenanthrene degradation through a fungal-bacterial consortium.

Fungal-bacterial consortia enhance organic pollutant removal, but the underlying mechanisms are unclear. We used stable isotope probing (SIP) to explore the mechanism of bioaugmentation involved in polycyclic aromatic hydrocarbon (PAH) biodegradation in petroleum-contaminated soil by introducing the indigenous fungal strain Aspergillus sp. LJD-29 and the bacterial strain Pseudomonas XH-1. While each strain alone increased phenanthrene (PHE) degradation, the simultaneous addition of both strains showed no significant enhancement compared to treatment with XH-1 alone. Nonetheless, the assimilation effect of microorganisms on PHE was significantly enhanced. SIP revealed a role of XH-1 in PHE degradation, while the absence of LJD-29 in 13C-DNA indicated a supporting role. The correlations between fungal abundance, degradation efficiency, and soil extracellular enzyme activity indicated that LJD-29, while not directly involved in PHE assimilation, played a crucial role in the breakdown of PHE through extracellular enzymes, facilitating the assimilation of metabolites by bacteria. This observation was substantiated by the results of metabolite analysis. Furthermore, the combination of fungus and bacterium significantly influenced the diversity of PHE degraders. Taken together, this study highlighted the synergistic effects of fungi and bacteria in PAH degradation, revealed a new fungal-bacterial bioaugmentation mechanism and diversity of PAH-degrading microorganisms, and provided insights for in situ bioremediation of PAH-contaminated soil.IMPORTANCEThis study was performed to explore the mechanism of bioaugmentation by a fungal-bacterial consortium for phenanthrene (PHE) degradation in petroleum-contaminated soil. Using the indigenous fungal strain Aspergillus sp. LJD-29 and bacterial strain Pseudomonas XH-1, we performed stable isotope probing (SIP) to trace active PHE-degrading microorganisms. While inoculation of either organism alone significantly enhanced PHE degradation, the simultaneous addition of both strains revealed complex interactions. The efficiency plateaued, highlighting the nuanced microbial interactions. SIP identified XH-1 as the primary contributor to in situ PHE degradation, in contrast to the limited role of LJD-29. Correlations between fungal abundance, degradation efficiency, and extracellular enzyme activity underscored the pivotal role of LJD-29 in enzymatically facilitating PHE breakdown and enriching bacterial assimilation. Metabolite analysis validated this synergy, unveiling distinct biodegradation mechanisms. Furthermore, this fungal-bacterial alliance significantly impacted PHE-degrading microorganism diversity. These findings advance our understanding of fungal-bacterial bioaugmentation and microorganism diversity in polycyclic aromatic hydrocarbon (PAH) degradation as well as providing insights for theoretical guidance in the in situ bioremediation of PAH-contaminated soil.

Advances in the Removal of Organic Pollutants from Water by Photocatalytic Activation of Persulfate: Photocatalyst Modification Strategy and Reaction Mechanism.

Environmental pollution caused by persistent organic pollutants has imposed big threats to the health of human and ecological systems. The development of efficient methods to effectively degrade and remove these persistent organic pollutants is therefore of paramount importance. Photocatalytic persulfate-based advanced oxidation technologies (PS-AOTs), which depend on the highly reactive SO4·- radicals generated by the activation of PS to degrade persistent organic pollutants, have shown great promise. This work discusses the application and modification strategies of common photocatalysts in photocatalytic PS-AOTs, and compares the degradation performance of different catalysts for pollutants. Furthermore, essential elements impacting photocatalytic PS-AOTs are discussed, including the water matrix, reaction process mechanism, pollutant degradation pathway, singlet oxygen generation, and potential PS hazards. Finally, the existing issues and future challenges of photocatalytic PS-AOTs are summarized and prospected to encourage their practical application. In particular, by providing new insights into the PS-AOTs, this review sheds light on the opportunities and challenges for the development of photocatalysts with advanced features for the PS-AOTs, which will be of great interests to promote better fundamental understanding of the PS-AOTs and their practical applications.

Novel nanohybrid iron (II/III) phthalocyanine-based carbon nanotubes as catalysts for organic pollutant removal: process optimization by chemometric approach.

In the present study, two iron phthalocyanine (FePc)-based nanocatalysts were synthesized and fully characterized. The carbon nanotubes (CNT) functionalized in an easy way with either Fe(II)Pc or Fe(III)Pc exhibit a very good catalytical activity. The activity in real wastewater effluent was comparable with the activity in distilled water. The procedure of modeling and optimizing with the assistance of chemometrics, utilizing design of experiments (DOE) and response surface methodology (RSM), revealed the conditions of optimum for decaying Reactive Yellow 84 on the nanocatalysts FePc_CNT. These optimal conditions included a catalyst dose of 1.70 g/L and an initial concentration (C0) of 20.0 mg/L. Under the indicated optimal conditions, the experimental findings verified that the removal efficiency was equal to Y = 98.92%, representing the highest observed value in this study. Under UVA light, after only 15 min of reaction, over 94% of dye was removed using both catalysts. The reuse experiments show that the activity of both nanohybrid material based on FePc-CNT slightly decreases over four consecutive runs. The quenching experiments show that RY84 was removed through radical pathways (O2•- and •OH) as well as non-radical pathways (1O2 and direct electron transfer).

MOF-derived CuO@CB@CF cathode for O2 activation to generate ROSs for efficient electro-Fenton-catalysis

The generation of reactive radicals by molecular oxygen activation has become an important advanced oxidation technique. The combination of highly active carbon materials and stable transition metal oxides can activate molecular oxygen to produce hydrogen peroxide and further produce active free radicals at the same time, which is an efficient way for the removal of organic pollutants by heterogeneous electro-Fenton (HEF) system. In this study, a novel metal organic framework (MOF) derived CuO-carbon black-carbon felt (CuO@CB@CF) composite catalytic electrode has been prepared, which can generate H2O2 efficiently by selective O2 reduction through two-electron pathway with high pollutant removal efficiency. By optimizing the calcination temperature of MOF and loading capacity, the MOF-derived CuO@CB@CF has demonstrated excellent performance as a HEF catalytic electrode. Meanwhile, the effects of applied voltage, pH value, electrode area and aeration conditions have been studied. The excellent performance of MOF-derived CuO@CB@CF provides new insights into the removal of organic pollutants through electro-Fenton processes of transition metal oxide and carbon-based catalysts.

Highly efficient electrocatalysis of oxygen to hydroxyl radical by FeN2O2 single-atom catalyst for refractory organic pollutant removal

The heterogeneous electro-Fenton (Hetero-EF) provides an effective and environmentally friendly method for refractory pollutants removal by strongly oxidative •OH. However, the •OH generation shows an insufficient activity in activating H2O2 to •OH due to the too strong H2O2 binding on the catalytic site. Here, an iron single-atom FeN2O2 catalyst anchored on hollow spherical porous carbon (FeN2O2-HPC) was designed to enhance •OH production by modulating the H2O2 binding. The FeN2O2-HPC Hetero-EF system showed a •OH production rate of 25.0 μmol h−1 and kinetic rate constant of 2.06 h−1 for phenol removal, which exceeded the FeN4 catalyst (the most reported iron single-atom). Density function theory calculations revealed that FeN2O2 could lower the H2O2 adsorption energy and energy barrier of H2O2 activation to •OH compared with FeN4, thus enhancing •OH production. This work gives a new insight into the •OH generation enhancement of Hetero-EF by modulating single-atom coordination environment for refractory pollutants removal.

High-performance internal circulation anaerobic granular sludge reactor for cattle slaughterhouse wastewater treatment and simultaneous biogas production

This research investigates the efficacy of a high-performance pilot-scale Internal Circulation Anaerobic Reactor inoculated with Granular Sludge (ICAGSR) for treating cattle slaughterhouse wastewater while concurrently generating biogas. The primary objective is to assess the efficiency and performance of ICAGSR in terms of organic pollutant removal and biogas production using granular anaerobic sludge. The research methodology entails operating the ICAGSR system under ambient conditions and systematically varying key parameters, including different Hydraulic Retention Times (HRTs) (24, 12, and 8 h) and Organic Loading Rates (OLRs) (3.3, 6.14, and 12.83 kg COD/m³. d). The study focuses on evaluating pollutants’ removal and biogas production rates. Results reveal that the ICAGSR system achieves exceptional removal efficiency for organic pollutants, with Chemical Oxygen Demand (COD) removal exceeding 74%, 67%, and 68% at HRTs of 24, 12, and 8 h, respectively. Furthermore, the system demonstrates stable and sustainable biogas production, maintaining average methane contents of 80%, 76%, and 72% throughout the experimental period. The successful operation of the ICAGSR system underscores its potential as a viable technology for treating cattle slaughterhouse wastewater and generating renewable biogas. In conclusion, this study contributes to wastewater treatment and renewable energy production by providing a comprehensive analysis of the ICAGSR system’s hydrodynamic properties. The research enhances our understanding of the system’s performance optimization under varying conditions, emphasizing the benefits of utilizing ICAGSR reactors with granular sludge as an effective and sustainable approach. Identifying current gaps, future research directions aim to further refine and broaden the application of ICAGSR technology in wastewater treatment and renewable energy initiatives.

Achievements in Preparation of Cyclodextrin–Based Porous Materials for Removal of Pollutants

Cyclodextrin–based porous materials have been widely applied in removing various organic pollutants from water environments, due to their unique physical and chemical properties, like the size–matching effect and hydrophobic interaction. Large numbers of hydroxyl groups in its external structure give cyclodextrin a high solubility in water, but the existence of these hydroxyl groups also endows cyclodextrin with the ability to be chemically modified with various functional groups to reduce its solubility in water and, meanwhile, to develop some novel functionalized cyclodextrin–based porous materials for selective removal of the target organic pollutants. This review focuses on the recent development in the synthesis of cyclodextrin–based porous materials (crosslinked cyclodextrin polymers and immobilized cyclodextrins), as well as highlighting their applications and mechanisms in the removal of dyes, endocrine disruptors, and mixed pollutants from water. Finally, the challenges and future perspectives in related research fields are discussed.

Urchin-like Ni-Fe-Mo sulfide: An effective electrochemical calcium sulfite activator for tetracycline degradation

Sulfite is deemed as a promising precursor to produce highly reactive species for contaminants remediation. Herein, the urchin-like Ni-Fe-Mo sulfide (NiFeMoSx) was anchored in-situ on nickel foam as a cathode to activate CaSO3 for efficient degradation of tetracycline (TC) under natural condition. The degradation efficiency reached 92.7% within 60 min, which was about 1.81 times higher than that of the electro-Fenton process based on NiFeMoSx. The beneficial performance came from the synergistic activation of CaSO3 by simultaneous rapid redox cycles of Fe(II)/Fe(III) and Ni(II)/Ni(III) on the NiFeMoSx cathode. Specifically, the primary intermediates Fe(II)-HSO3- and Ni(II)-SO32- triggered a series of radical chain reactions, accompanied the reduction of Ni(III)/Fe(III) by electrochemistry and electron donor of Mo(IV) and S2- on the surface of the catalyst. The regeneration of the Fe(II)/Ni(II) was quickly realized and subsequently triggered the chain reactions, which would accelerate the formation rate of reactive species, such as SO4∙−, ·OH, O2∙− and 1O2, of which 1O2 and O2•- played important roles on degradation TC. This work provides a promising application for the efficient removal of persistent organic pollutants by metal sulfide activated sulfite.

UV/H2O2 produced degradation of 2,4-D and 4-CPA

2,4-dichlorophenoxyacetic (2,4-D) acid and 4-chlorophenoxyacetic acid (4-CPA), as widely utilized organochlorine pesticides, are normally detected in wastewater and atmosphere. Their harmfulness to the ecosystem cannot be ignored. UV/H2O2 is one of the most conventional advanced oxidation processes, which has remarkable advantages for the removal of refractory organic pollutants in wastewater. However, the reaction mechanisms and pathways of pollutants with reactive radicals are still unclear. In this study, the degradation efficacy and mechanisms during the photodegradation of 2,4-D and 4-CPA in UV/H2O2 processes were investigated by experiments and density functional theory calculations. The results showed that 2,4-D was more likely to be degraded by UV/H2O2 treatment than UV photolysis alone. In contrast, 4-CPA can be degraded effectively and rapidly under UV irradiation alone. By LC-MS analysis, the degradation products of 2,4-D and 4-CPA in the UV/H2O2 processes were identified and they were produced by hydroxylation and photolysis. Therefore, we speculated a competition mechanism presented between direct photolysis and indirect photolysis in the UV/H2O2 degradation of 2,4-D and 4-CPA. The OH-initiated reaction mechanisms of 2,4-D and 4-CPA in aqueous environments were investigated using quantum chemical methods SMD/M06–2X/6–311++G (3df, 2p)//SMD/M06–2X/6-311 + G (d,p). The pH dependence of the reaction mechanisms and rate constants in their degradation process induced by ·OH was also investigated. The calculation results showed that the ionic forms (2,4-D- and 4-CPA-) were more prone to react with ·OH in comparison to the corresponding molecular forms (2,4-D and 4-CPA). The total rate constants of 2,4-D and 4-CPA with OH increased with the pH from 1 to 10, and decreased with continued pH increase. The toxicities of 2,4-D, 4-CPA and their products were assessed by the QSAR-based toxicity evaluation software. The results showed that several products were more toxic than their parent compounds, such as 2,4-dichlorophenol, 3,5-dichlorocatechol, 4-chlorophenol and hydroquinone. This work can contribute to clarifying the environmental risks of 2,4-D and 4-CPA and offer a complete understanding for the photodegradation behavior of 2,4-D and 4-CPA in aqueous ecosystems.

Sustainable removal of organic pollutants using biochar based ZnO composites: Experimental and theoretical studies of remediation process

The tailoring of biochar to enhance its remediation efficiency for removal of pollutants from water has been a hot topic these days. Fabricating two different biochar materials using metal oxide nano particles in four ratios has been done in this work. The synthesized materials have been characterized by XRD, surface functional groups were analyzed using FTIR and XPS, band gap calculation were carried out using Tauc's method, recombination of charges was studied using photoluminescence spectroscopy, morphological, textural properties and elemental analysis was done using SEM, BET, TGA, EIS and EDX analysis. The removal of organic pollutants including phenol, dibutyl phthalate and gallic acid up to 91.6%, 84% and 95% was observed employing these composites. The band gap reduction from 3.1 eV to 2.5 eV and 2.8 eV was observed in case of ZW(1-10) and ZP(1-10) respectively. The formation of Zn-O-C bond in the composite could be possible reasons for the band gap reduction and excellent performance exhibited by the composite. The results highlight the influence of functional groups on the efficiency of synthesized material. Furthermore, density functional theory (DFT) calculations were performed using Gaussian16 software to propose the adsorption mechanism for the observed results. The energy calculation for different binding modes were carried out. Theoretical findings agreed with the empirically demonstrated remediation mechanism.

Selective oxidation behavior based on iron-doped MOF derived carbon-based catalysts: Active site regulation and degradation mechanism analysis

Selective removal of target organic pollutants in complex water quality of municipal sewage is extremely important for the deep treatment of water quality. Here, energetic MOF and Fe-MOF are doped in electrostatic spinning process to adjust the structure and composition of the catalysts, active oxygen species (ROSs), realizing the selective removal of organic pollutants. Non-azo and azo pollutants are selected as target pollutants. Catalysts PCFe-8 with Fe nanoclusters, EPCFe-8 with Fe-Nx, and EPC-8 without Fe doping are used to activate peroxymonosulfate (PMS) for degrading pollutants. The results show that the PCFe-8/PMS system can produce the most SO4− and exhibit superior removal of azo pollutants, whereas the degradation behavior of non-azo pollutants is more inclined to occur in the EPCFe-8/PMS system and the EPC-8/PMS system. This work provides a reference for elucidating the relationship between catalyst structure and components, types of ROSs, and selective degradation of pollutants.

Air-engaged synthesis of yeast biomass-derived porous O, p-codoped biochar as metal free catalyst towards water decontamination

Facile and sustainable preparation of effective metal-free catalysts using natural biomass as a feedstock is essential but challenging for peroxymonosulfate activation in degrading organic pollutants in wastewater. In this study, we develop an air-engaged pyrolysis method to successfully prepare O, P dual-doped porous carbon material (Yeast-T) using biomass yeast as a feedstock. Among the samples, Yeast-650 exhibits the highest performance in activating peroxymonosulfate towards the destruction of methyl orange, achieving a removal efficiency of 98 % in 30 min and a rate constant of 0.226 min−1. The non-radical pathway, with singlet oxygen as the active substance, dominates the destruction of methyl orange over the Yeast-650/peroxymonosulfate system. Based on the detected intermediates, four possible pathways for methyl orange degradation by the Yeast-650/peroxymonosulfate system are unveiled. The toxicity analysis of the degradation products was evaluated by calculating and comparing the radicle length of mung bean in different solutions and the germination of wheat seeds in different solutions. This study presents a simple and feasible air-mediated synthetic method for high-performance metal-free peroxymonosulfate activators in the removal of organic pollutants.

Tailored anthraquinone-based covalent organic frameworks boosted atrazine degradation through peroxymonosulfate activation driven by visible light

Atrazine (ATZ), a wildly used s-triazine herbicide to avoid grassy insects and weeds, causes biological and environmental issues due to its prolonged existence and various toxic properties. Peroxymonosulfate (PMS) photoactivation-based advanced oxidation processes (AOPs) meet the challenges of sustainable energy and environmental concerns, and thus are promising challenging for ATZ degradation. However, preparing photocatalysts to realize efficient ATZ degradation remains challenging. Here, we prepared the highly efficient visible-light photocatalyst with abundant anthraquinone groups, i.e. TpDQ-COF, which was employed to activate PMS for fast and efficient ATZ degradation. ATZ degradation in the TpDQ-COF/PMS system reached 0.127 min−1 under visible light (VL), which is ca. 17.9 times that of TpDA-COF without anthraquinone. It implies that anthraquinone units served as pivotal active sites for facilitating photoelectron separation and migration, which triggered ROS generation towards highly effective ATZ degradation. In addition, the radical-quenching and Electron Paramagnetic Resonance (EPR) experiments proved that •OH, •SO4- and 1O2 played pivotal roles in ATZ degradation under TpDQ-COF/PMS/VL system. The ATZ degradation pathways included dealkylation, dechlorination-hydroxylation, alkylic-hydroxylation, and alkylic-oxidation, which were confirmed by intermediates and density functional theory (DFT) analysis. Overall, TpDQ-COF showcased its excellent practical utility in the removal of organic pollutants in contaminated water.

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 Fenton performance of wet-mechanochemically synthesized FeS2/Biochar: The multiple synergistic effect derived from mutual element doping

FeS2-biochar composites have been considered as promising heterogeneous Fenton materials for pollutants removal. However, the chemical synthesis of element-doped FeS2-biochar composite with superior performance and the comprehensive investigation for its underlying multiple synergistic mechanism remain a difficult endeavor. Herein, a novel FeS2/Biochar nanocomposite with mutual element doping was firstly synthesized by facile wet-mechanochemical method using iron, sulfur and bamboo-biochar for efficient organic pollutant (sulfamonomethoxine, SMM) removal. Experiment and DFT calculation results revealed that multiple synergistic effect between FeS2 and biochar derived from newly formed Fe-C and C-S-C bonds induced the abundant reactive oxygen species (ROS) and excellent electron transfer capacity. Fe-C sites facilitated the H2O2 adsorption and populated O-O bond in H2O2 for its barrierless dissociation into •OH via forming bridging C-Fe-O-O-Fe bond. Oxygen vacancy, C-S-C and Fe-C bonds, persistent free radicals (PFRs) accelerated the generation and transformation of ROS, which resulted in dominating free radical (•OH, •O2–, •SO4-) and auxiliary non-radical (1O2) pathway. Meanwhile, Fe3+/Fe2+ redox-cycle was expedited by electron donor/shuttle (S22-, BC, •O2–, C-S-C and Fe-C bonds). All these specialties contributed to the superior performance of FeS2/Biochar Fenton system for SMM removal at wide pH range (3–11) with negligible Fe release. Completely SMM (50 mg/L) removal was achieved within 20 min for 8 successive reuses. This work emphasized the concept of building mutual element doping on molecular level in enhancing FeS2-Biochar synergy towards efficient environmental remediation.

Construction of Z-scheme heterojunction ZIF-8-decorated ZnO/SiO2 for enhanced visible-light photocatalytic removal of organic pollutants and reduction of Cr (VI)

The zeolitic imidazolate framework-8 (ZIF-8) demonstrates promising photocatalytic activity in wastewater treatment. Nevertheless, limited visible light utilization and arduous recyclability hinder its practical application. Herein, we fabricated ZIF-8 decorated zinc oxide/silica (ZnO/SiO2) hollow spheres by an in-situ strategy. This composite effectively photocatalytically degrades organic dyes and reduces Cr (VI) under the simulated sunlight. Results reveal that Z-scheme heterojunction construction between ZIF-8 and ZnO/SiO2 is formed and facilitates the effective separation and transport of electrons and holes, leading to nearly complete methylene blue (MB) degradation, 88.7 % of rhodamine B (RhB) removal, and 41.8 % Cr (VI) reduction within 30 min. Notably, the ZIF-8/ZnO/SiO2 composite exhibits enhanced visible-light utilization attributed to its reduced band gap (3.04 eV), thereby improving MB degradation compared to using solely ultraviolet light. Furthermore, the composite demonstrates remarkable reusability and stability, achieving over 99 % removal rate for MB after four photocatalysis cycles with minimal structural and morphological changes. This work demonstrates the remarkable photocatalytic activity ZIF-8/ZnO/SiO2 with its improved visible-light response, highlighting the potential of using modified ZIF-8 materials as promising and sustainable catalysts for wastewater treatment.

Preparation of modified wood-based metal nanoparticles synthesized in situ and efficient removal of organic pollutants from wastewater

Wood has excellent properties such as biodegradability, high reactivity and rich channel skeleton structure. However, the defects such as hole blockage and limited specific surface area limit the application of wood-based materials in wastewater treatment. Therefore, in this research, wood substrates (DTWS) were treated using a deep eutectic solvent method, which was able to remove both lignin and hemicellulose from wood. Wood-based carriers with high specific surface area and high chemical activity were formed. The DTWS-Ag material was formed by growing Ag nanoparticles (NPs) in wood channels by hydrothermal method. The results showed that with the increase of lignin and hemicellulose removal, the degradation performance of DTWS-Ag material showed a volcanic trend due to the interaction between Ag and the inner wall of the pipe. The pore size and the amount of Ag NPs are very important to the degradation rate of dye molecules. DTWS-4-Ag composite material makes wood pore diameter and Ag NPs production reach a high balance, so that it has the highest degree of reduction. DTWS-4-Ag showed high catalytic degradation efficiency and stability for methylene blue degradation, with the degradation efficiency up to 98.3%. This low-cost, renewable wood-based filter has high dye degradation efficiency and can be widely used in practical wastewater treatment.

Bi-ZFO/BMO-Vo Z-scheme heterojunction photocatalysis-PMS bidirectionally enhanced coupling system for environmental remediation

Given the urgency of organic pollutant removal and the low efficiency of advanced oxidation processes (AOPs), a novel Bi-ZFO/BMO-Vo photocatalyst was fabricated via the solvothermal method. A coupling system was constructed to combine photocatalysis with peroxymonosulfate (PMS) oxidation processes, which synergistically degrade organic pollutants. Bi-ZFO/BMO-Vo exhibited excellent photocatalytic performance, which could remove 100% RhB in 110 min and degrade 100% MG in 70 min, and 88% H-TC in 50 min. The excellent catalytic performance of Bi-ZFO/BMO-Vo was not only attributed to the synergistic effect of PMS activation and photocatalysis, but also attributed to the SPR effect of Bi nanoparticles, electron capture of oxygen vacancies, and intense contact of Bi-ZFO/BMO-Vo heterojunctions. The active species capture experiments and EPR tests indicated that 1O2, SO4–·, ·OH, and O2–· worked together for the RhB removal. The degradation intermediates of RhB were identified by LC-MS. Based on the experimental results, the band structure and Z-scheme charge transfer mechanism were proposed. Toxicity evaluation indicated that Bi-ZFO/BMO-Vo-Vis/PMS could significantly reduce RhB toxicity. This efficient and stable catalyst is expected to be used in organic wastewater degradation and practical applications.