Organic Degradation Research Articles

Organic Carbon Reaction Kinetics in Bioturbated Sediments

AbstractMost organic carbon delivered to the seafloor is degraded within the bioturbated layer. Theory and empirical evidence have shown that organic carbon reactivity relates to the age of a particle. However, due to particle mixing, the age‐depth linear relation induced by sediment accretion is obfuscated. Here we combine a Lagrangian particle tracking model that resolves the age distribution of particles in the bioturbated zone and couple it to age‐dependent organic carbon degradation. Depth profiles for organic carbon concentration, reactivity and degradation rate are presented for sediments receiving low and high reactivity organic carbon in coastal, continental slope and deep‐sea environments. Our results show that a simple first‐order kinetics model suffices for well‐mixed sediments and systems receiving pre‐processed materials. A reactive continuum approach is needed for poorly mixed sediments receiving highly reactive organic carbon and for sediments below the bioturbated layer.

Chiral FeNC single-atom nanozymes with multi-enzyme activity for dye degradation

The application of single-atom nanozymes in the removal of organic dye pollution by advanced oxidation process (AOPs) have been widely concerned. However, the application of single-atom nanozymes in AOPs is rarely reported. In this work, a kind of Fe-and nitrogen-codoped carbon (Fe-N-C) with peroxidase-like and laccase-like activities was prepared by calcining Fe-doped MOF, then the chiral peptides were introduced into single-atom nanozymes, and chiral single-atom nanozymes (L-Au@FeNC) were successfully prepared. The L-Au@FeNC can effectively activate PMS to degrade different kinds of organic dyes and also shows high cycle stability. In addition, the results of quenching experiment and electron paramagnetic resonance (EPR) test show that 1O2 produced during PMS activation plays an important role in the degradation of organic dyes, and O2·-, ·OH, and SO4·- are also produced during PMS activation, suggesting that the degradation of selected organic dyes include radical and non-radical pathways. It should be noted that L-Au@FeNC showed higher activity than D-Au@FeNC in enzyme-like activity (laccase-like and peroxidase-like) experiment and organic dye degradation, the results of molecular docking simulation indicated that it may be due to the better binding force of L peptide to the substrate of enzyme-like reaction and organic dye than D peptide. This chiral single-atom nanozymes provide a new idea for the application of organic dye degradation and enzyme-like catalysis design.

Bi2MoO6/MgIn2S4 S-scheme heterojunction with rich oxygen vacancies for effective organic pollutants degradation: Degradation pathways, biological toxicity assessment, and mechanism research

Designing and constructing novel photocatalysts for organic pollutant degradation is of critical significance for water environment treatment. Constructing a Bi2MoO6/MgIn2S4 (BMO/MIS) S-scheme heterojunction with oxygen vacancies, which efficiently removed RhB within visible light irradiation. Oxygen vacancies regulated the band structure of Bi2MoO6 (BMO) and enhanced the adsorption of RhB on the catalyst's surface. The S-scheme heterojunctions contributed to the separation and transfer of photo-generated charge, retained the optimal redox ability of Bi2MoO6-Vo (BMO-Vo) and MgIn2S4 (MIS) at the same time. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) further confirmed the S-scheme charge transfer mechanism and the presence of oxygen vacancies. Within 30 min of visible light irradiation, RhB was completely degraded by BMO/MIS-8%, while the degradation efficiency of RhB by BMO-Vo and MIS were only 39.93 % and 80.87 %, respectively. The kinetics constant is 0.1035 min−1 of BMO/MIS-8%, which was 20.29 and 1.95 times that of BMO-Vo and MIS, respectively. At the same time, BMO/MIS-8% achieved removal efficiency of 24.28 %, 56.53 %, 59.15 % and 100 % for MO, TC,H-TC and MB, respectively. Compared to the previously synthesized Bi-ZFO/BMO-Vo photocatalyst, BMO/MIS-8% demonstrated superior degradation efficiency, exhibiting a degradation kinetic constant that was 2.12 times greater than that of Bi-ZFO/BMO-Vo under visible light irradiation. To improve the practical application of BMO/MIS, the effects of pH, co-existing ions and types of pollutants on degradation efficiency were evaluated. In addition, the biological toxicity assessment showed a significant decrease in the toxicity of RhB degradation products. This work provides a feasible avenue for constructing Bi2MoO6-based heterojunctions to treat dye wastewater.

The surface electron transfer strategy promotes the hole of PDI release and enhances emerging organic pollutant degradation

In semiconductor photocatalysts, the easy recombination of photogenerated carriers seriously affects the application of photocatalytic materials in water treatment. To solve the serious problem of electron−hole pair recombination in perylene diimide (PDI) organic semiconductors, we loaded ferric hydroxyl oxide (FeOOH) on PDI materials, successfully prepared novel FeOOH@PDI photocatalytic materials, and constructed a photo-Fenton system. The system was able to achieve highly efficient degradation of BPA under visible light, with a degradation rate of 0.112 min−1 that was 20 times higher than the PDI system, and it also showed universal degradation performances for a variety of emerging organic pollutants and anti-interference ability. The mechanism research revealed that the FeOOH has the electron trapping property, which can capture the photogenerated electrons on the surface of PDI, effectively reducing the compounding rate of photogenerated carriers of PDI and accelerating the iron cycling and H2O2 activation on the surface of FeOOH at the same time. This work provides new insights and methods for solving the problem of easy recombination of carriers in semiconductor photocatalysts and degrading emerging organic pollutants.

Simplistic preparation of Sn-doped MgIn2S4 for photocatalytic organic dye degradation under visible light irradiation

Simplistic preparation of Sn-doped MgIn2S4 for photocatalytic organic dye degradation under visible light irradiation

Statistical analysis and optimization of mechanical-chemical electro-Fenton for organic contaminant degradation in refinery wastewater

Refinery wastewater (RWW) poses significant environmental challenges due to its high concentration of organic contaminants, necessitating effective treatment solutions. This study employs the mechanical design of the Electro-Fenton (EF) technique as a feasible alternative for treating RWW. The anode and cathode electrodes, made of stainless steel and iron, respectively, were utilized to conduct organic removal (OR) from RWW. To maximize performance, two metric optimization design techniques were examined: Box Behnken Design (BBD) and response surface methodology. The analysis of variance revealed a high coefficient of determination value (R2 = 0.9685), indicating a second-order provable relationship between the response and self-governing variables. Additional statistical analysis was performed to assess the validity and reliability of the suggested approach. A predictive regression model was developed based on unresolved values, demonstrating a high level of agreement with experimental values. This model identified the optimal equation for the empirical model to predict OR based on predetermined parameters. Based on the BBD, the percentage of OR reached 93.45 % at pH 3, temperature, and electrolysis time of 60 °C, and 30 minutes, respectively. The implications of this study suggest that the optimized Electro-Fenton technique could serve as a robust solution for addressing the environmental impact of RWW, contributing to sustainable wastewater management practices.

Nanostructured NiCo2S4 immobilized on nickel foam as recyclable catalyst for activating peroxymonosulfate toward doxycycline degradation: Performance and mechanism

The existing powder catalysts used in sulfate radical-based advanced oxidation processes (SR-AOPs) commonly suffer from severe limitation due to the difficulty of recycling and inadequate exposure of the active site. In this work, spinel sulfide (NiCo2S4) was uniformly grown on 3D nickel foam (NF) through a one-step hydrothermal route for the activation of peroxymonosulfate (PMS) toward highly efficient degradation of doxycycline (DOX). Due to the synergistic effect of Ni and Co in the NiCo2S4, the NiCo2S4/NF (0.6 g/L) combined with PMS (3.0 mmol L-1) can promote a nearly complete degradation (98.2 %) toward 0.3 mmol/L DOX within 6 min. Density functional theory (DFT) calculations illustrated that the NiCo2S4/NF can adsorb PMS through a unique Ni-S-Co structure and “conducting bridge” mode of NF, accelerating the electron transfer from NiCo2S4/NF to PMS and the subsequent O-O bond cleavage. Especially, the Co/Ni dual-site enhanced the adsorption of PMS and promotes electron transfer to form surface-activated PMS complex (catalyst-PMS*), leading to the generation of surface-bound reactive oxygen species (ROS) on the NiCo2S4 surface. Quenching experiments and ESR tests demonstrated that radicals such as SO4•-, 1O2, •OH and surface-bound ROS play a vital role in DOX degradation. Moreover, the potential mechanism and pathway of DOX degradation are reasonably deduced by investigating and analyzing the intermediates with liquid chromatography-mass spectromsetry (LC-MS). Consequently, this study provides a deep insight on the systhsis of spinel sulfide and its intrinsic mechanism of PMS activation toward organic contaminant degradation.

Micro-nano bubbles in action: AC/TiO2 hybrid photocatalysts for efficient organic pollutant degradation and antibacterial activity

Developing highly active and sustainable photocatalysts is crucial for environmental remediation. This work focuses on the enhanced photocatalytic degradation efficiency of synthetic dyes using TiO2-coated AC hybrid photocatalysts under MNB aeration. The TiO2-coated AC hybrid photocatalyst (HP) was synthesized via a sol-gel method and characterized using XRD, FTIR, SEM, EDS, HR-TEM, and DRS. The study investigated the photocatalytic degradation of three dyes indigo carmine (IC), reactive black 5 (RB5), and methylene blue (MB) in wastewater, with initial dye concentrations ranging from 10 to 100 μM. Under UVA irradiation, the hybrid photocatalyst with MNB aeration (HP + UVA + MNB) achieved the highest degradation efficiencies of 69.09%, 60.06%, and 55.19% for IC, MB, and RB5, respectively. Further analysis showed that the chromophores and complex structures of these dyes were broken into intermediate products. The Langmuir-Hinshelwood kinetic model was used to describe the reaction mechanisms. The HP + UVA + MNB system demonstrated superior photocatalytic degradation activity, making it suitable for operational and environmental applications in dye wastewater treatment. Additionally, the antibacterial properties of AC and HP were tested at 100 μg/mL, showing effectiveness against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli.

Enhanced dye degradation using MIL-53(Fe)-Modified kraft lignin as a heterogeneous Fenton catalyst

MIL-53(Fe), a metal–organic framework (MOF), is capable of degrading harmful organic contaminants, but it has relatively low Fenton catalytic efficiency. To enhance the degradation performance of MIL-53(Fe), we synthesized MIL-53(Fe)-MKL by incorporating modified kraft lignin (MKL) into pristine MIL-53(Fe). The as-prepared composite demonstrated Fenton activity, degrading 97 % of methylene blue (MB) within 50 min. Compared to pristine MIL-53(Fe) (which achieved 62.4 % MB degradation), the MIL-53(Fe)-MKL composite showed a 34.6 % improvement in MB degradation under identical reaction conditions. The incorporated MKL promotes Fe2+ regeneration from Fe3+ in the Fenton process, activating H2O2 to produce OH radicals, which were identified through scavenging experiments and chemical dosimetry with ESR analysis. The MIL-53(Fe)-MKL composite was reused for at least five cycles without a significant decrease in catalytic efficiency. This reported catalyst takes advantage of both MKL and MIL-53(Fe) to enhance catalytic activity, providing a basis for developing innovative catalysts for organic pollutant degradation.

Higher-valent nickel oxides with enhanced two-electron oxygen reduction in advanced electro-Fenton system for organic pollutants degradation

A higher-valent NiO catalyst, enriched with trivalent Ni (Ni3+) and exposed {111} crystal facets, was developed to enhance selective two-electron oxygen reduction (2e– ORR) for electrochemical hydrogen peroxide (H2O2) production, leading to highly efficient organic pollutant removal. The catalyst was synthesized via a precipitation method, incorporating crystal facet and cation vacancy engineering to expose active sites. It demonstrated 96 % selectivity and 59 A g−1 mass activity, attributed to weakened *OOH binding, as shown by density functional theory. Integrated into an advanced electro-Fenton (EF) flow cell, the system achieved 100 % removal of 200 mL of 50 ppm bisphenol A (BPA) in 4 minutes, with 93 % total organic carbon removal within 2 hours. This study provides a scalable and efficient solution for decentralized environmental remediation and wastewater treatment.

Degradation of organic dyes by Peroxymonosulfate activated with Zn/Co-ZIF

In this study, we successfully synthesized a bimetallic metal-organic framework material Zn/Co-ZIF to start Peroxymonosulfate (PMS) for organic dye degradation in the water body. Material characterization was evaluated by advanced methods, such as XRD, FT-IR, SEM, EDX, and BET. The influence of different factors on methylene blue (MB) decomposition rate was investigated. The results show that Zn/Co-ZIF has a porous structure, a high specific surface area and decomposes 98.22% MB (20 mg/L) in 4 minutes under reaction conditions of 40 mg/L catalyst, 0.814mM PMS, pH = 7. The decomposition efficiency of dyes increases in the order CR (79.85%) <RhB (90.81 %) < DB71 (96.07%) < MO (97.63%) < MB (98.22%). The main ROS for the degradation MB in this study were SO4—-, O2—- and 1O2. This shows that Zn/Co-ZIF materials are potential heterogeneous catalysts to activate PMS to decompose organic pollutants in water.

Visible-light induced effective and sustainable remediation of nitro organics pollutants using Pd-doped ZnO nanocatalyst

Nitroaromatic compounds represent a class of highly toxic pollutants discharged into aquatic environments by various industrial activities, posing significant threats to ecological integrity and human health due to their persistent and hazardous nature. In this study, Pd-doped ZnO nanoparticles were investigated as a potential solution for the degradation of nitro organics, offering heightened photocatalytic efficacy and prolonged stability. The synthesis of Pd-doped ZnO NPs was achieved via the hydrothermal method, with subsequent analysis through XRD spectra and XPS confirming successful Pd doping within the ZnO matrix. Characterization through FESEM and HRTEM unveiled the heterogeneous morphologies of both undoped and Pd-doped ZnO nanoparticles. Additionally, UV–vis and PL spectroscopy provided insights into the optical properties, chemical bonding, and defect structures of the synthesized Pd-doped ZnO NPs. Pd doping induces a redshift in ZnO’s absorption spectra, reducing the bandgap from 3.12 to 2.94 eV as Pd concentration rises from 0 to 0.2 wt.%. The photocatalytic degradation, following pseudo-first-order kinetics, achieved 90% nitrobenzene abatement (200 µg/L, pH 7) under visible light within 320 min with a catalyst loading of 16 µg/mL. The photocatalytic efficacy of 0.08 wt% Pd-doped ZnO (k = 0.058 min⁻1) exhibited a 25-fold enhancement compared to bare ZnO (k = 3.1 × 10–4 min-1). Subsequent quenching and ESR experiments identified hydroxyl radicals (OH•) as the predominant active species in the degradation mechanism. Mass spectrometry analysis unveiled potential breakdown intermediates, illuminating a plausible degradation pathway. The investigated Pd-doped ZnO nanoparticles demonstrated reusability for up to five successive treatment cycles, offering a sustainable solution to nitro organics contamination challenges.

Engineering ceria oxide with nickel doping and rich oxygen vacancies for enhanced electrocatalytic degradation of aromatic organics

Aromatic dyes are widely applicable in the textile, leather, and ink industries yet receive serious contamination issues to water bodies, soil, and even air. Herein, we develop an efficient electrocatalytic oxidation method for degrading aromatic dyes via developing supportive CeO2-based electrode materials decorating with highly dispersive Ni and rich oxygen vacancies. The decorating Ni species are in situ converted from a composite of CeO2 nanocrystals and formamide-derived polyaminoimidazole (PAI)-coordinated Ni to ensure the high dispersion of Ni species. The decomposition of PAI ligands also helps to create the localized reductive atmosphere for the generation of rich surface oxygen vacancies, which further benefits the enhancement of electronic conductivity and charge transport ability. The effects of Ni doping concentrations, Rhodamine B (RhB, as a simulating aromatic dye) concentrations, pH of RhB solution, types and concentrations of electrolytes, and working current densities on the degradation performance are comprehensively investigated. Electrocatalytic measurements reveal that the CeO2 catalyst with optimal Ni concentration and fine single-crystal sizes of 5.5 ± 0.03 nm (termed as Ni0.025-CeO2-x) exhibits very promising degradation efficiency (96.9 %) and structural durability (repeated use for 5 cycles with limited activity decrease).

Porous aromatic framework with active carbonyl sites as a metal-free peroxymonosulfate activator for organic contaminants degradation: Free radical and non-radical pathway mechanisms

Transition metal-based catalysts used in advanced oxidation processes may encounter problems of metal ion leaching. Therefore, advanced oxidation processes initiated by metal-free carbon catalysts are regarded as competitive solutions for environmental remediation. In light of this, we have prepared PAF-145, a porous aromatic framework containing carbonyl groups (C = O) that serves as a stable and eco-friendly metal-free carbon catalyst for activating peroxymonosulfate. The stable structure and abundant C = O groups of PAF-145 endow it with excellent degradation performance, good reusability and adaptability to a wide pH range and environments with various coexisting anions. PAF-145 degraded 98.7 % of Rhodamine B within 20 min, achieving a reaction rate constant that was 48.5 times higher than that of PAF without carbonyl groups. PMS is oxidized to 1O2 and O2•− on the electron-deficient carbon atoms within the carbonyl groups. Using quenching experiments, electron paramagnetic resonance analysis, and electrochemical tests, it was determined that the degradation of Rhodamine B is primarily governed by both a non-radical pathway that includes 1O2 and the electron transfer mechanism, as well as a radical pathway that involves O2•− in the PAF-145/PMS system.

Efficient degradation of methylene blue and HCHO by nonmetallic B-doped g-C3N5: activity and mechanism analysis

To solve the pollution of natural water bodies by organic dyes and the exceeding of indoor HCHO standards caused by renovation, the study realized the band gap modulation of g-C3N5, a novel semiconductor photocatalytic material, by using H3BO3 as a source of nonmetallic B. The prepared B/g-C3N5 has shown excellent photocatalytic performance and stability for organic dye degradation in water bodies and indoor HCHO removal. The degradation rate of methylene blue (MB) reached 95% in 60 min of visible light, and the removal rate of HCHO reached 96.3% in 180 min of visible light. The MB and HCHO were efficiently degraded to small molecule inorganic compounds such as CO2 and H2O under the oxidation of active groups such as ·O2 − and h+. The doping of nonmetallic B realizes the efficient separation of e−-h+ of g-C3N5, improve the absorption performance of visible light, and broaden the spectral range significantly. The modulation of the g-C3N5 band gap provides a potential application scenario for the development of novel photocatalytic materials.

Unveiling the positive impacts of the genus Rhodococcus on plant and environmental health

Organic farming has emerged as a sustainable solution to the adverse effects (diminished nutritional value, compromised food quality, environmental contamination, and public health hazards) that are usually associated with harmful chemical pesticides. To overcome such loss, one must explore the plant-associated microbes that are the naturally occurring root commensal and could positively improve crop health. In this review, we highlight the importance of the bacterial genus Rhodococcus, a subset of Actinobacteria that carries immense potential in enhancing crop yield and is associated with bioremediation of toxic pesticides and other chemicals to improve soil health. However, it has been noticed that few species of Rhodococcus are pathogenic for the plant (R. fascians) as well as humans/animals (R. equi). But still, the majority of Rhodococcus isolates are found to be non-pathogenic and carry substantial beneficial traits. Here, we have attempted to comprise those beneficial traits of the different members of the genus Rhodococcus. The main emphasis of this review article is to explore the major areas such as enzyme production, phytohormone synthesis, growth regulation, siderophore production, bioremediation, organic compound degradation, and environmental pollution control. Opinions towards the applications of advanced methodologies for utilizing the cumulative prospective potential of the genus Rhodococcus have also been discussed in the different sections of the review. Conclusively, this article gathers the scattered information from the past and recent literature about this bacteria and provides the future direction about how it can improve plant/soil health and eliminate toxic chemicals and environmental pollutants.

Prepared copper oxide nanoparticle colloidal solution by different laser ablation energy in liquid for enhanced organic dye degradation efficiency

Prepared copper oxide nanoparticle colloidal solution by different laser ablation energy in liquid for enhanced organic dye degradation efficiency

Bioelectricity drives transformation of nitrogen and perfluorooctanoic acid in constructed wetlands: Performances and mechanisms

In this study, constructed wetland-microbial fuel cell (CW-MFC) filled with modified basalt fiber (MBF) via iron modification was utilized for treating perfluorooctanoic acid (PFOA) containing sewage. Results showed the significant promotion by bioelectricity on ammonium and total nitrogen by 7.80–8.14 %. Although such enhancement was suppressed by PFOA, higher removal was still observed with closed circuit, and PFOA removal also increased by 9.05 %. Bioelectricity contributed to enrichment of bacteria involved in nitrifying (Nitrospira and Ellin6067), denitrifying (like Thauera and Dechloromonas), iron redox (Geobacter), and sulfate-reducing (Desulfobacter), aligned with up-regulated of functional genes, including amoA, narG , napA, narK, narS, nrfA, sulp and sqr. Enrichment of autohydrogenotrophic and sulfide-oxidizing autotrophic denitrifiers, and nitrate dependent iron oxidation bacteria by bioelectricity all promoted denitrification. Moreover, bioelectricity boosted relative abundance of organic compounds degradation enzymes, such as dehydrogenase, decarboxylase, and dehalogenase, supporting the enhancement on PFOA removal. Generally, PFOA was converted to short-chain perfluorocarboxylic acids (PFCAs) via decarboxylation, hydroxylation, HF elimination, hydrolysis, F- elimination, C-C bond scission, and dehydration in CW-MFC. The final PFCAs-products determined was perfluorobutyric acid. This work estimated feasibility of treating PFOA containing sewage by CM-MFC, and offered new insights on enhancing mechanisms of nitrogen and PFOA conversion.

BiOCl-PVDF nanofibrous membrane for synergic oil-water separation and degradation of dye

Polymeric membranes have garnered remarkable attention, attributed to the significant breakthrough in the filtration of oily wastewater. However, the major setbacks of pristine polymeric membranes include susceptibility to fouling and chemical instability. Addressing such issues, this work focusses in the modification of polymer membranes using a metal oxyhalide, such as Bismuth oxychloride (BiOCl). This modification not only enhances water purification capabilities but also strengthens the membrane, protecting it from environmental deterioration and extending its lifespan. BiOCl was integrated into an electrospun pristine nanofibrous polymeric membrane using hydrothermal technique. The synthesized membrane matrix displayed superhydrophilicity and underwater superoleophobicity, effectively separating oil-in-water mixtures and emulsions. Moreover, BiOCl was effectively utilized to assess organic pollutant adsorption and degradation through photocatalysis. In addition, the membrane exhibited exceptional recyclability and withstood harsh conditions, contributing to its mechanical stability. The numerous advantages, enhance the effectiveness of BiOCl modified membrane in water pollution remediation.

Captivating 2H-MoS2 nanoflowers for efficient NH3 detection and photocatalytic dye degradation

This research unveils the gas sensing and photocatalytic potential of 2H-MoS2 nanoflowers, offering a promising solution for ammonia sensing and wastewater remediation. The 2H phase of MoS2 nanoflowers is synthesized via a simple one-step hydrothermal method using ammonium heptamolybdate and thiourea. The elemental and morphological study confirms the formation of the 2H phase of MoS2 nanoflowers with an average sheet thickness of 14 nm. The XRD and HR-TEM analysis findings are in good accordance with the interlayer spacing of MoS2, calculated to be 0.64 nm. The 2H-MoS2 nanomaterial based chemiresistive sensor is tested for six different targets (NH3, C2H5OH, C3H6O, C3H7OH, HCHO, and C6H5CH3) and shows good selectivity towards ammonia (NH3) with the highest response of 81 %. The response-recovery time, repeatability, concentration, and humidity-based analysis are conducted for the analysis of the sensor. The fabricated 2H-MoS2 based sensor shows a response time of 8.5 s and a recovery time of 4.3 s. Furthermore, three model water contaminated dyes, MB, MO, and RB, are chosen for the photocatalytic experiment under visible light irradiation. The reusability, relative degradation, and pseudo-first-order analysis are used to evaluate the photocatalytic dye degradation properties of 2H-MoS2 nanoflowers. The reaction rate constant of 2H-MoS2 nanomaterials for MB, MO, and RB dyes is calculated to be (0.05010) min−1, (0.03458) min−1, and (0.02516) min−1, respectively. The maximum degradation efficiency of 2H-MoS2 nanoflowers towards MB, MO, and RB dye is 95 %, 86 %, and 76 %, respectively, under visible light irradiation. These findings suggest that the hydrothermally synthesized 2H-MoS2 nanoflowers have multifunctional applications such as effective NH3 sensors as well as photocatalysts for organic dye degradation, paving the way for more efficient and sustainable gas sensing and wastewater treatment technologies.