Degradation Of Triclosan Research Articles

Deciphering the triclosan degradation mechanism in Sphingomonas sp. strain YL-JM2C: Implications for wastewater treatment and marine resources

Triclosan (TCS), an antimicrobial agent extensively incorporated into pharmaceuticals and personal care products, poses significant environmental risks because of its persistence and ecotoxicity. So far, a few microorganisms were suggested to degrade TCS, but the microbial degradation mechanism remains elusive. Here, a two-component angular dioxygenase (TcsAaAb) responsible for the initial TCS degradation was characterized in Sphingomonas sp. strain YL-JM2C. Whole-cell biotransformation and crude enzyme assays demonstrated that TcsAaAb catalyzed the conversion of TCS to 4-chlorocatechol and 3,5-dichlorocatechol rather than the commonly suggested product 2,4-dichlorophenol. Then two intermediates were catabolized by tcsCDEF cluster via an ortho-cleavage pathway. Critical residues (N262, F279, and F391) for substrate binding were identified via molecular docking and mutagenesis. Further, TcsAaAb showed activity toward methyl triclosan and nitrofen, suggesting its versatile potential for bioremediation. In addition, TCS-degrading genes were also present in diverse bacterial genomes in wastewater, ocean and soil, and a relatively high gene abundance was observed in marine metagenomes, revealing the transformation fate of TCS in environments and the microbial potential in pollutant removal. These findings extend the understanding of the microbe-mediated TCS degradation and contribute to the mining of TCS-degrading strains and enzymes, as well as their application in the bioremediation of contaminated environments.

Sequential Reductive Dechlorination of Triclosan by Sediment Microbiota Harboring Organohalide-Respiring Dehalococcoidia.

Aquatic ecosystems represent a prominent reservoir of xenobiotic compounds, including triclosan (TCS), a broad-spectrum biocide extensively used in pharmaceuticals and personal care products. As a biogeochemical hotspot, the potential of aquatic sediments for the degradation of TCS remains largely unexplored. Here, we demonstrated anaerobic biotransformation of TCS in a batch microcosm established with freshwater sediment. The initial 43.4 ± 2.2 μM TCS was completely dechlorinated to diclosan, followed by subsequent conversion to 5-chloro-2-phenoxyphenol, a monochlorinated TCS (MCS) congener. Analyses of community profile and population dynamics revealed substrate-specific, temporal-growth of Dehalococcoides and Dehalogenimonas, which are organohalide-respiring bacteria (OHRB) affiliated with class Dehalococcoidia. Dehalococcoides growth was linked to the formation of diclosan but not MCS, yielding 3.6 ± 0.4 × 107 cells per μmol chloride released. A significant increase in Dehalogenimonas cells, from 1.5 ± 0.4 × 104 to 1.5 ± 0.3 × 106 mL-1, only occurred during the reductive dechlorination of diclosan to MCS. Dehalococcoidia OHRB gradually disappeared following consecutive transfers, likely due to the removal of sediment materials with strong adsorption capacity that could alleviate TCS's antimicrobial toxicity. Consequently, a solid-free, functionally stable TCS-dechlorinating consortium was not obtained. Our results provide insights into the microbial determinants controlling the environmental fate of TCS.

Efficient Photocatalytic Degradation of Triclosan and Methylene Blue by Synthesized Ag-Loaded ZnO under UV Light

Industrial discharge of hazardous organic and synthetic chemicals, such as antibacterials and dyes, poses severe risks to human health and the environment. This study was conducted to address the urgent need for efficient and stable zinc-oxide-based photocatalysts to degrade such pollutants. A novel approach to synthesizing silver-loaded zinc oxide (Ag@Z) catalysts was introduced by using a simple and efficient combination of hydrothermal and precipitation methods. Comprehensive characterization of Ag@Z photocatalysts was performed using XRD, XPS, Raman, UV–vis adsorption, FTIR, and SEM, revealing an enhancement of structural, optical, and morphological properties in comparison to pure zinc oxide. Notably, the 5%Ag@Z catalyst exhibited the highest degradation efficiency among the other synthesized catalysts under UV-C light irradiation, and enhanced the degradation rate of pure zinc oxide (Z) by 1.14 and 1.64 times, for Triclosan (TCS) and Methylene Blue (MB), respectively. the effect of catalyst dose and initial concentration was studied. A mechanism of degradation was proposed after investigating the effect of major reactive species. The 5%Ag@Z catalyst increased the photostability, which is a major problem of zinc oxide due to photocorrosion after reusability. We found that 50% and 74% of energy consumption for the photocatalytic degradation of TCS and MB by 5%Ag@Z, respectively, was saved in compassion with zinc oxide. The remarkable photocatalytic performance and the good recovery rate of Ag@Z photocatalysts demonstrate their high potential for photocatalytic degradation of organic contaminants in water.

TiO2/Al-PILC Catalysts Synthesized from a Non-Conventional Aluminum Source of Aluminum and Applied in the Photodegradation of Organic Compounds

AbstractThis study explores the transformative potential of Pillared InterLayered Clays (PILC) derived from non-conventional aluminum sources as catalytic supports in the synthesis of TiO2/catalysts for the efficient photodegradation of organic pollutants in water. Montmorillonite (Mt) and three alumina-pillared montmorillonite (PILC) synthesized using various aluminum sources, were impregnated with titanium to synthesize TiO2/catalysts. The successful synthesis of these materials was confirmed through several characterization techniques such as X-ray diffraction (XRD), N2 adsorption-desorption at -196 ºC, morphological analysis using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and Energy-Dispersive X-ray Spectrometry (EDX). The photolysis, adsorption, and catalytic behavior of the TiO2/catalysts were studied for the degradation of triclosan (TCS), 2,6-dichlorophenol (2,6-DCP), and bisphenol A (BPA). All synthesized catalysts surpassed the efficacy of commercial anatase, with TiO2/Al-PILC exhibiting superior performance in comparison to TiO2/Mt. Photodegradation was most effective under UV radiation, with TCS demonstrating the highest degradation (approximately 70%). Notably, Al-PILC samples, particularly those synthesized from saline slags, displayed enhanced properties. Among them, TiO2/Al-PILCAE exhibited the highest degradation rates under both UV and visible light, underlining the remarkable potential of saline slags as precursors for Al-PILC synthesis. This study provides valuable insights into the design and development of efficient catalysts for water treatment applications, paving the way for sustainable and effective solutions in the realm of environmental remediation.

Triclosan Dioxygenase: A Novel Two-component Rieske Nonheme Iron Ring-hydroxylating Dioxygenase Initiates Triclosan Degradation.

The emerging contaminant triclosan (TCS) is widely distributed both in surface water and in wastewater and poses a threat to aquatic organisms and human health due to its resistance to degradation. The dioxygenase enzyme TcsAB has been speculated to perform the initial degradation of TCS, but its precise catalytic mechanism remains unclear. In this study, the function of TcsAB was elucidated using multiple biochemical and molecular biology methods. Escherichia coli BL21(DE3) heterologously expressing tcsAB from Sphingomonas sp. RD1 converted TCS to 2,4-dichlorophenol. TcsAB belongs to the group IA family of two-component Rieske nonheme iron ring-hydroxylating dioxygenases. The highest amino acid identity of TcsA and the large subunits of other dioxygenases in the same family was only 35.50%, indicating that TcsAB is a novel dioxygenase. Mutagenesis of residues near the substrate binding pocket decreased the TCS-degrading activity and narrowed the substrate spectrum, except for the TcsAF343A mutant. A meta-analysis of 1492 samples from wastewater treatment systems worldwide revealed that tcsA genes are widely distributed. This study is the first to report that the TCS-specific dioxygenase TcsAB is responsible for the initial degradation of TCS. Studying the microbial degradation mechanism of TCS is crucial for removing this pollutant from the environment.

A novel cobalt-iron bimetallic hydrochar for the degradation of triclosan in the aqueous solution: performance, reusability, and synergistic degradation mechanism

Low activation performance is a critical issue limiting the practical application of low-cost biochar in the advanced oxidation. Given the high potential of transition metals in the persulfate activation process and abundant oxygen-containing groups of hydrochar, hydrochar derived from cobalt (Co)-modified iron (Fe)-enriched sludge was synthesized and its performance and activation mechanism for the degradation of triclosan were investigated. Co modification significantly altered the morphology of hydrochar, and the increased Co–Fe mass ratios transformed hydrochar from granular to rose-shaped lamellar and then to helical sheet structures. Specific surface area, defect degree, and oxygen-containing groups of hydrochar increased with increasing cobalt-iron mass ratios. The highest removal of triclosan was up to 98% in the hydrochar/peroxymonosulfate (PMS) system under a wide range of pHs (3–10) and still remained higher than 90% after four cycles. Both Radical (mainly hydroxyl radical) and nonradical pathways (singlet oxygen and electron transfer) were evidenced to play roles in the triclosan removal. Fe3+ promoted the regeneration of Co2+ and realized the efficient circulation of Co3+/Co2+. A ternary system consisting of electron donor (triclosan)-electron mediator (hydrochar)-electron acceptor (PMS) provided channels for electron transfer. No measurable Co and Fe were released during the reaction, and the toxicity of degradation intermediates was lower than that of triclosan. Beside triclosan, rhodamine B, bisphenol A, sulfamethoxazole, and phenol were also almost degraded completely in this oxidation system. This study provides a promising way for the enhancement of catalytic activity of carbonaceous material.

CNTs/Ce co-doped PbO2 anode for electro-oxidation of triclosan: Fabrication, kinetics, and degradation mechanism based on DFT calculations

In this study, an efficient Ti/SnO2-Sb2O3/CNT-Ce-PbO2 electrode was fabricated for triclosan electro-oxidation by co-doping the transition metal Ce and carbon nanotubes (CNTs) into the PbO2 active layer. Characterization results show that the co-doped Ce and CNTs present a synergistic effect on covering the obvious cracks on the Ti/SnO2-Sb2O3 surface, decreasing the PbO2 crystal size, increasing the electrode oxygen evolution potential from 1.60 to 2.17 V vs SCE, and reducing the charge transfer resistance by 66 %. Consequently, Ti/SnO2-Sb2O3/CNT-Ce-PbO2 was the most effective and energy-efficient electrode for hydroxyl radical (•OH) generation and triclosan electro-oxidation in this study. Compared with other two electrodes (Ti/SnO2-Sb2O3 and Ti/SnO2-Sb2O3/Ce-PbO2), triclosan removal by Ti/SnO2-Sb2O3/CNT-Ce-PbO2 was accelerated by 1.8–2.6 times, with the energy demand for abating 90 % triclosan (EEO) decreased by 49 % – 67 %. Furthermore, triclosan degradation pathways were proposed based on density functional theory (DFT) calculation and transformation product (TP) identification, with •OH addition at C14 and C11 sites being the most favorable pathway. In addition, the estimated acute and chronic toxicities of TPs were generally decreased than their mother compound. Therefore, the results of this study suggest the feasibility and effectiveness of the Ti/SnO2-Sb2O3/CNT-Ce-PbO2 electrode for triclosan electro-oxidation.

Critical roles of soil composition and pollutant properties on the degradation of PPCPs during ferrous/persulfate processes

Pharmaceuticals and personal care products (PPCPs) are widely used worldwide and cause potential soil pollution. Fe2+-activated persulfate (PS) processes (Fe-PAPs) are promising techniques for soil remediation. However, a knowledge gap exists in the mechanistic insights into the dominant factors affecting the degradation of different PPCPs in varied soil types. This study systematically investigated the roles of soil components and pollutant properties in the degradation of three PPCPs (triclosan (TCS), triclocarban (TCC), and naproxen (NPS)) in the nine soils in the Fe2+/PS system. The degradation efficiencies of TCS and NPS ranged from 10.92 % to 91.62 % and 46.59 % to 99.81 %, respectively, whereas nearly no degradation was observed for TCC. PPCPs with high water solubility, high energies of the highest occupied molecular orbital (EHOMO), low pKa values, low energy gap (ΔE), or low vertical ionization potential (VIP) were more favorable for degradation. XPS analysis suggested that aliphatic carbon (Ali–C–C(H)), ether or alcohol carbon (C–O), and aldehyde or ketonic carbon (CO) on SOM significantly inhibited TCS degradation. The results of ROS quenching experiments showed that SO4•− and 1O2 played major roles in TCS and NPS degradation in the six soils, with the relative contributions ranged from 24.82 % to 99.14 % and 0.15 % to 73.40 %, respectively. The interaction between soil components, active species, and pollutants resulted in the distinct intermediates of TCS and NPS in different soils. Our findings provide in-depth insights into the role of soil composition and pollutant properties on the remediation of PPCP-contaminated soils in Fe-PAPs.

Tailoring CuOx loading on CoFe2O4 nanocubes photocatalyst for superior photocatalytic degradation of triclosan pollutants under VL irradiation and toxicological evaluation

In this study, we report the development of a novel CuOx(3 wt%)/CoFe2O4 nanocubes (NCs) photocatalyst through simple co-precipitation and wet impregnation methods for the efficient photocatalytic degradation of triclosan (TCS) pollutants. Initially, rod-shaped bare CoFe2O4 was synthesized using a simple co-precipitation technique. Subsequently, CuOx was loaded in various percentages (1, 2, and 3 wt%) onto the surface of bare CoFe2O4 nanorods (NRs) via the wet impregnation method. The synthesized materials were systematically characterized to evaluate their composition, structural and electrical characteristics. The CuOx(3 wt%)/CoFe2O4 NCs photocatalyst exhibited superior photocatalytic degradation efficiency of TCS (89.9%) compared to bare CoFe2O4 NRs (62.1 %), CuOx(1 wt%)/CoFe2O4 (80.1 %), CuOx(2 wt%)/CoFe2O4 (87.0 %) under visible light (VL) irradiation (λ ≥ 420 nm), respectively. This enhanced performance was attributed to the improved separation effectiveness of photogenerated electron (e−) and hole (h+) in CuOx(3 wt%)/CoFe2O4 NCs. Furthermore, the optimized CuOx(3 wt%)/CoFe2O4 NCs exhibited strong stability and reusability in TCS degradation, as demonstrated by three successive cycles. Genetic screening on Caenorhabditis elegans showed that CuOx(3 wt%)/CoFe2O4 NCs reduced ROS-induced oxidative stress during TCS photocatalytic degradation. ROS levels decreased at 30, 60, and 120-min intervals during TCS degradation, accompanied by improved egg hatching rates. Additionally, expression levels of stress-responsible antioxidant proteins like SOD-3GFP and HSP-16.2GFP were significantly normalized. This study demonstrates the efficiency of CuOx(3 wt%)/CoFe2O4 NCs in degrading TCS pollutants, offers insights into toxicity dynamics, and recommends its use for future environmental remediation.

Effects of reduced graphene oxide nanomaterials on transformation of 14C-triclosan in soils

Increasing use and release of graphene nanomaterials and pharmaceutical and personal care products (PPCPs) in soil environment have polluted the environment and posed high ecological risks. However, little is understood about the interactive effects and mechanism of graphene on the behaviors of PPCPs in soil. In the present study, the effects of reduced graphene oxide nanomaterials (RGO) on the fate of triclosan in two typical soils (S1: silty loam; S2: silty clay loam) were investigated with 14C-triclosan, high-resolution mass spectrometry, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT) calculations, and microbial community structure analysis. The results showed that RGO prolonged the half-life of triclosan by 23.6–51.3 %, but delayed the formation of transformed products such as methyl triclosan and dechlorinated dimer of triclosan in the two typical soils. Mineralization of triclosan to 14CO2 was inhibited by 48.2–79.3 % in 500 mg kg−1 RGO in comparison with that in the control, whereas the bound residue was 54.2–56.4 % greater than the control. RGO also reduced the relative abundances of triclosan-degrading bacteria (Pseudomonas and Sphingomonas) in soils. Compared to silty loam, RGO more effectively inhibited triclosan degradation in silty clay loam. Furthermore, the DFT calculations suggested a strong association of the adsorption of triclosan on RGO with the van der Waals forces and π-π interactions. These results revealed that RGO inhibited the transformation of 14C-triclosan in soil through strong adsorption and triclosan-degrading bacteria inhibition in soils. Therefore, the presence of RGO may potentially enhance persistence of triclosan in soil. Overall, our study provides valuable insights into the risk assessment of triclosan in the presence of GNs in soil environment.

Degradation of carbamazepine and triclosan in sewage sludge mixtures used for fertilizing agricultural soils

Degradation of carbamazepine and triclosan in sewage sludge mixtures used for fertilizing agricultural soils

Optimized preparation of Ni-Febm bimetallic particles by ball milling NiSO4 and iron powder for efficient removal of triclosan

The excessive usage and emissions of triclosan (TCS) pose a serious threat to aquatic environments. Iron-based bimetallic particles (Pd/Fe, Ni/Fe, and Cu/Fe, etc.) were widely used for the degradation of chlorophenol pollutants. This study proposed a novel synthesis method for the preparation of Ni/Fe bimetallic particles (Ni-Febm) by ball milling microscale zero valent iron ZVI (mZVI) and NiSO4. Ball-milling conditions such as ball-milling time, ball-milling speed and ball-to-powder ratio were optimized to prepare high activity Ni-Febm bimetallic particles. During the ball-milling process, Ni2+ was reduced to Ni0 and formed a coupled structure with ZVI. The amount of Ni0 on ZVI significantly affected the activity of Ni-Febm bimetallic particles. The highest activity Ni-Febm bimetallic particles with Ni/Fe ratio of 0.03 were synthesized under optimized conditions, which could remove 86.56% of TCS (10 μM) in aerobic aqueous solution within 60 min. In addition, higher particle dosage, lower pH condition and higher reaction temperature were more conducive for TCS degradation. The higher corrosion current and lower electron transfer impedance of Ni-Febm bimetallic particles were the main reasons for its high activity. The hydrogen atom (•H) on the surface of Ni-Febm bimetallic particles was mainly contributed to the removal of TCS, as reductive transformation products of TCS were detected by LC-TOF-MS. Notably, a small amount of oxidation products were discovered. The total dechlorination rate of TCS was calculated to be 39.67%. After eight reaction cycles, the residual Ni-Febm bimetallic particles could still degrade 28.34% of TCS within 6 h. Low Ni2+ leaching during reaction indicated that Ni-Febm bimetallic particles did not pose potential environmental risks. The prepared environmental-friendly Ni-Febm bimetallic particles with high activity have great potential in the degradation of other chlorinated organic compounds in wastewater.

Effects of dissolved organic matter from sludge pyrolysis biochar on the triclosan removal from contaminated soil

When sludge biochar (SC) prepared from sewage sludge was used to remove triclosan (TCS) from both aqueous solution and soil, the adsorption capacity increased with increasing pyrolysis temperature, while the degradation rate showed a different pattern, namely, SC-500 > SC-800 > SC-600 > SC-700. TCS degradation rate achieved nearly 100 % at 2 h with SC-500 used as a Fenton catalyst. Aromaticity of dissolved organic matter (DOM) was positively correlated with the degradation of TCS and adding homologous DOM solution shortened the equilibrium time of TCS degradation, while removing DOM from SC prolonged, compared to the original SC. The results of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectrometer (EPR) characterization indicated that SC-500 performed a stronger catalytic degradation ability due to the relatively high Fe2+ content to produce more ∙OH and SC-derived DOM act as an electron shuttle to promote other reactive oxidative species generation through two free radical pathways in the activation of H2O2 by Fe2+, which in turn promoted the degradation of TCS.

Comparative Kinetic Analysis of Triclosan Degradation under UV-C and Simulated Solar Irradiation

This research delves deeply into the intricate degradation kinetics of triclosan, employing two distinct methodologies: UV and simulated solar irradiation. Through a comprehensive comparative analysis, the study endeavors to elucidate the efficacy of these techniques, aiming to shed light on their respective methodological strengths and limitations. The study compares the efficacy of UV and simulated solar irradiation techniques for triclosan degradation, revealing that both methods exhibit effectiveness in degrading triclosan, with variations observed in degradation rates and byproduct formation. Through a detailed examination of the kinetics of triclosan degradation, the study reveals the intricate pathways and mechanisms involved in the photodegradation process. Results highlight the influence of irradiance levels and residence times on degradation efficiency. The research identifies optimal conditions for triclosan degradation, emphasizing the importance of residence time and irradiance levels. Results show that a residence time of 4 h and an irradiance level of 450 W m−2 maximize degradation efficiency. Analysis of degradation byproducts provides insights into the transformation pathways of triclosan under UV and simulated solar irradiation, indicating the formation of 2,4-dichlorophenol, quinone, and hydroquinone as primary byproducts.

Unveiling microbial degradation of triclosan: Degradation mechanism, pathways, and catalyzing clean energy

Emerging organic contaminants present in the environment can be biodegraded in anodic biofilms of microbial fuel cells (MFCs). However, there is a notable gap existing in deducing the degradation mechanism, intermediate products, and the microbial communities involved in degradation of broad-spectrum antibiotic such as triclosan (TCS). Herein, the possible degradation of TCS is explored using TCS acclimatized biofilms in MFCs. 95% of 5 mgL−1 TCS are been biodegraded within 84 h with a chemical oxygen demand (COD) reduction of 62% in an acclimatized-MFC (A-MFC). The degradation of TCS resulted in 8 intermediate products including 2,4 -dichlorophenol which gets further mineralized within the system. Concurrently, the 16S rRNA V3–V4 sequencing revealed that there is a large shift in microbial communities after TCS acclimatization and MFC operation. Moreover, 30 dominant bacterial species (relative intensity >1%) are identified in the biofilm in which Sulfuricurvum kujiense, Halomonas phosphatis, Proteiniphilum acetatigens, and Azoarcus indigens significantly contribute to dihydroxylation, ring cleavage and dechlorination of TCS. Additionally, the MFC was able to produce 818 ± 20 mV voltage output with a maximum power density of 766.44 mWm−2. The antibacterial activity tests revealed that the biotoxicity of TCS drastically reduced in the MFC effluent, signifying the non-toxic nature of the degraded products. Hence, this work provides a proof−of−concept strategy for sustainable mitigation of TCS in wastewaters with enhanced bioelectricity generation.

Promoted electrochemical degradation of triclosan with persulfate on Fe-Ni oxide modified graphite felt cathode

Advanced oxidation processes (AOPs) based on persulfate (PS) have shown great potential in wastewater treatment. In this work, FeNiO-modified Graphite felts (GF) cathodes (FeNiO/GF) were prepared to construct an activation system for electrochemical activation of persulfate (EA-PS). The effect of condition parameters (current density, PS concentration and pH) on the degradation of triclosan (TCS) in the EA-FeNiO/GF-PS system was investigated. The results showed that FeNiO loaded on the GF enhanced the cathodic activation of PS. The EA-FeNiO/GF-PS system showed excellent degradation of various pollutants at PS concentration of 1.0 mM and current density of 10 mA/cm2. Electron paramagnetic resonance and free radical quenching experiments showed that •OH, SO4•–, O2•– and 1O2 all contributed to the degradation of triclosan (TCS), with SO4•– and •OH being the major free radicals. The electrochemical performance tests and the XPS characterization of the FeNiO electrode results demonstrated that the valence cycling of Fe and Ni was accelerated under the action of an electric field. In addition, FeNiO/GF had excellent reusability and was unaffected by the actual water matrices. This study provided an effective strategy for the degradation of organic pollutants in water treatment.

Eco-friendly and stable triclosan removal from groundwater using peroxyacetic acid activated with biochar produced from saccharification residues

Biochar is a cost-effective activator in advanced oxidation processes, its progressive release of soluble substances during application can potentially reduce the stability of its activation efficiency and induce secondary environmental pollution. Addressing these drawbacks of biochar, this study focused on enhancing its stability and the efficacy of peracetic acid (PAA) in removing triclosan from groundwater, employing a saccharification residue-based biochar (BC-SR). The research findings indicated that the efficacy of triclosan removal by BC-SR/PAA surpassed that of ordinary biochar (BC-O) by 1.33 times. Furthermore, utilizing the response surface methodology design, the synergistic efficiency of BC-SR/PAA was enhanced, achieving a removal rate of up to 90%. The high removal efficiency of BC-SR could be attributed to its microporous structure, surface area, loss of stability, and thermal stability, which were all significantly better than BC-O. Even after 10 cycles of reuse, the removal efficiency of BC-SR still maintained 77% of its initial efficiency. Notably, the activation mechanism of BC-SR/PAA was different from typical carbonaceous materials, as the degradation system's main active substances were ·O2− and 1O2, and BC-SR's active sites may be its surface's persistent free radicals. Moreover, column tests using natural groundwater and soil emulated BC-SR's role as a permeable reactive barrier. Results underscored the BC-SR/PAA system's formidable removal and anti-interference abilities. Analysis showed triclosan degradation products have lower toxicity, highlighting their practical value. This research addresses the challenge of inadequate removal efficiency and secondary pollution in in-situ groundwater remediation, particularly associated with complex substrates. This approach, unlike biochar ‘burdening’, offers a novel concept for ‘de-burdening’ biochar activation.

Peroxymonosulfate activation by ruthenium in homogeneous systems for degradation of triclosan: Comparison between Ru(II) and Ru(III)

Triclosan (TCS) as an emerging pollutant in aquatic environments poses great threats to human health and ecological safety, hence ruthenium (Ru) as a potential transition-metal catalyst was utilized to activate peroxymonosulfate (PMS) and mitigate TCS pollutant in this study. The performances of Ru(II) species (i.e., Ru(bpy)32+) and Ru(III) species (i.e., RuCl3) were compared to systematically investigate the TCS removal capacity of Ru/PMS system in homogeneous systems. The experimental results show that the homogeneous Ru/PMS systems exhibited greater oxidization capacity than other analogous systems such as the Ru/H2O2 system and Fe/PMS system, while the Ru(III) activator had stronger activation capacity for PMS than the Ru(II) activator. Less dosage of Ru(III) (∼1/3 of the Ru(II) dosage) and less reaction time (∼1/4 of that in the Ru(III)/PMS system) were needed in the Ru(III)/PMS system to remove the same amount of TCS. Additionally, there were optimal values for the dosage of Ru species and PMS, while overdose might inhibit the TCS removal. Coexisting components in aquatic environments had similar effects on Ru(II)/PMS and Ru(III)/PMS systems. Cl- at low concentrations inhibited the removal of TCS, while Cl- at high concentrations improved the removal of TCS. HCO3–, Ca2+, Mg2+ and humic acid mainly inhibited the removal of TCS, and dissolved oxygen had a negligible influence. Based on quenching experiments and electron paramagnetic resonance (EPR) technique, the 1O2 played a major role in the homogeneous Ru/PMS systems, while •OH and SO4•- contributed less. Importantly, TCS can be degraded into less toxic intermediates in the Ru(III)/PMS system. This work can facilitate the development of efficient Ru(III)-based activators for organic pollutant remediation in aquatic environments.

Compact wirelessly-powered photocatalyst-coated spheres: Concept development and application for oxidative wastewater treatment and membrane fouling control

Wirelessly powered photocatalyst-coated spheres (WPS) were successfully developed and wirelessly powered from outside the reactor using resonant inductive coupling. Diverse applications of WPS were demonstrated for the visible light-assisted photocatalytic degradation of methylene blue (textile dye), diclofenac, and triclosan (pharmaceutical compounds) and fouling control of ceramic membranes. These catalyst-coated WPS successfully generated O2− as the main reactive oxygen species (ROS). As demonstrated, these WPS are low-cost, easy to fabricate, have excellent visible light sources, and can be used as the photocatalyst carrier. The acrylic shell of WPS is transparent to light with wavelengths from 300 to 800 nm. Increasing the number of WPS can increase the light intensity proportionally, and 8 WPS can be powered by one power coil outside the reactor. A higher quantity of WPS per reaction volume can be used to improve the reactivity, bringing the use of WPS reactors closer to industrial applications. This is the first report on the use of WPS in the ceramic membrane reactor for fouling control, a 50 % delay compared to control, and highlights the versatility of this system. This work would open up new exploration avenues for membrane fouling control using WPS-based heterogeneous photocatalysis.

Insight into the enhancement effect of humic acid on microbial degradation of triclosan in anaerobic sediments

Humic acid (HA) as one class of macromolecular substances plays important roles in mediating environmental behaviors of pollutants in sediments, but its effect on microbial degradation of triclosan (TCS), a common antibacterial drug, remains unclear. In this study, the effects of HA addition with different dosages (0–5%) on TCS degradation in anaerobic sediment slurries and the underlying microbial mechanisms were investigated. The results showed that HA addition significantly accelerated the TCS removal and the maximum removal percentage (30.2%) was observed in the sediment slurry with 5% HA addition. The iron reduction rate, relative abundances of the genera Comamonas, Pseudomonas and Geobacter, and bacterial network complexity in sediment slurry were significantly enhanced due to HA addition. Based on the partial least squares path modeling analysis, the enhancement effect of HA on TCS degradation was mainly explained by Fe(II):Fe(III) ratio with the highest influence on TCS removal (total effect: 0.723), followed by dominant genera abundances (total effect: 0.391), module relative abundance (total effect: 0.272), and network topological features (total effect: 0.263). This finding enhanced our understanding of the role of HA in TCS biodegradation in contaminated sediments for bioremediation purposes.