Degradation Of Triclosan Research Articles

Removal of triclosan in a Fenton-like system mediated by graphene oxide: Reaction kinetics and ecotoxicity evaluation

As a typical nanomaterial, graphene oxide (GO) can be easily dispersed in water and may affect the aqueous environment. In this paper, the degradation of triclosan (TCS) in a Fenton-like system Fe3+/H2O2 in GO aqueous solution was investigated. Interestingly, it was observed that GO at low concentration (2.0 mg/L) could exhibit significant catalytic effect on TCS removal. Meanwhile, results of XPS, Raman and TEM spectroscopy suggested the structure and chemical composition of GO did not exhibit significant change after the oxidation process within 30 min. As per the radical quenching experiments and ESR tests, hydroxyl radical (·OH) was mainly responsible for the decomposition of TCS. Further mechanism study indicated that the reaction activation energy (Ea) could be lowered and the production of ·OH be promoted in the presence of GO, respectively. A total of nine intermediates of TCS degradation were detected by TOF-LC-MS after SPE procedure. Finally, ecotoxicity assessment revealed that degradation of TCS by Fe3+/H2O2 system in GO aqueous solution could yield by-products of smaller toxicity compared with parent compounds.

Degradation of Triclosan in soils by thermally activated persulfate under conditions representative of in situ chemical oxidation (ISCO)

As a widely used antimicrobial agent, Triclosan (TCS) may potentially enter the environment, thus invoking significant environmental concerns due to its high toxicity to organisms. The present study demonstrated that a thermally activated persulfate (PS) oxidation process could effectively degrade the TCS in various arable topsoils. Eighty percent of the TCS at 50 mg kg−1 in Zhe Jiang (ZJ) soil could be degraded after a 360 min reaction in the presence of 18.8 mM of PS. Increased PS concentrations significantly increased the efficiency of the degradation. Elevated temperatures were favorable for TCS degradation, and the apparent activation energy Ea was determined to be 74.3 kJ mol−1. The oxidation efficiency gradually decreased with the increase of the pH from 3 to 11. An electron paramagnetic resonance (EPR) experiment and radical scavenging test confirmed that both OH and SO4− existed during oxidation, and SO4− was the dominant radical species. The degradation efficiency of TCS was higher than that of Triclocarban (TCC), another widely used antimicrobial agent, which might be attributed to the electro-donating phenolic (–OH) and ether (–O–) groups in the molecular structure of TCS. The degradation of TCS in three arable topsoils indicated that the soil organic matter played a dominant role in TCS degradation. In ZJ soil, after the oxidation process, the soil’s SOM was decreased by 14%, and the breakdown of large soil aggregates into smaller ones was found. Moreover, two degradation products of TCS were identified, e.g., penta-hydroxylated and hexa-hydroxylated TCS, which may be less toxic. The degradation was induced by phenol ring hydroxylation, and the underlying oxidation mechanisms are given.

Synthesis of Ag/BiVO4/rGO composite with enhanced photocatalytic degradation of triclosan

A ternary visible-light driven photocatalyst, Ag/BiVO4/reduced graphene oxide (rGO) composite was manufactured by hydrothermal strategy. The optimized products were characterized by XRD, SEM, HRTEM, EDS, XPS, DRS, Raman spectra, PL, BET, photocurrent density and EIS analysis. Compared to pure BiVO4, the fabricated ternary composite showed enhanced photocatalytic ability to decompose pollutant under visible light. Triclosan was completely removed after 100 min in solution with 1 mg/mL photocatalyst under visible light irradiation. Repeated cycle tests demonstrated the photo-stability and reusability of composite to decompose triclosan, indicating that this material could be utilized repeatedly. The upgraded photocatalytic ability was attributed to the addition of Ag and rGO, which enhanced the charge separation and inhibited the recombination of photogenerated electrons and holes. The EPR spin-trap technique (with DMPO) was performed to identify the radicals produced in Ag/BiVO4/rGO under the visible light, and trapping experiments were conducted to determine the main active species in the photocatalytic process of decomposing triclosan. Finally, seven reaction intermediates of triclosan were detected by LC-MS/MS and possible degradation routes were proposed.

Fate of triclosan, triclocarban, and their transformation products in wastewater under nitrifying conditions

The nitrification process was simulated using benchtop bioreactors to gain insight into the fate of the antimicrobials triclosan (TCS) and triclocarban (TCC), as well their transformation products, during wastewater treatment. Currently, little information exists on the impact of nitrification treatment on concentrations of TCC, TCC degradation products, and TCS degradation products. Reactors were run using samples collected from a large municipal wastewater treatment plant at two pH ranges (6.5–7.5 and 8.5–9.5) for 171 h to simulate an extended hydraulic retention time (HRT). TCS was degraded under both pH conditions, with a 28.5% overall reduction in solids samples when the pH range was 6.5–7.5 and an overall reduction of 83.2% in solids samples when the pH ranged 8.5–9.5. Methyltriclosan (MeTCS) was formed in solids samples during both treatment conditions. MeTCS formed the most rapidly during the first 25 h of treatment at pH 8.5–9.5. Levels of 2,4-dichlorophenol, a TCS photolysis product, and TCC did not change over the 171 h treatment period, indicating that nitrification is not an effective treatment for reduction of these compounds. Three TCC dechlorination products and triclosan-O-sulfate were not observed at or above the limit of quantitation in any bioreactor samples.

Simultaneous adsorption and degradation of triclosan by Ginkgo biloba L. stabilized Fe/Co bimetallic nanoparticles

Triclosan (TCS), an antimicrobial agent added in many pharmaceutical and personal care products, can cause some environmental problems due to its bioaccumulation, toxicity and potential antibiotic cross-resistance. In this study, Ginkgo biloba L. leaf extract was used as the green stabilizing agent to synthesize Fe/Co bimetallic nanoparticles (G-Fe/Co NPs), which were applied to remove TCS from aqueous solution. G-Fe/Co NPs were characterized by TEM, EDS, SEM, BET, FTIR, XRD and XPS. G. biloba L. leaf extract improved the dispersion and reduced the passivation of NPs. The TCS removal efficiency followed the order of G-Fe/Co NPs > G-Fe NPs > Co NPs > Fe/Co NPs > Fe NPs. G-Fe/Co NPs can be reused at least eight times. The Co leaching under different initial pH values was negligible. The factors affecting the TCS removal were investigated. The results indicated that the removal of TCS followed pseudo-second-order kinetics, and the removal rate constant decreased with increasing the initial pH value and the initial TCS concentration, and decreasing the Co loading of G-Fe/Co NPs and NPs dosage. The mass balance of TCS removal by G-Fe/Co NPs indicated that adsorption was dominant process and TCS degradation was an accumulative process.

An efficient graphene supported copper salen catalyst for the activation of persulfate to remove chlorophenols in aqueous solution

Schiff base metal complexes are effective homogeneous catalysts used in oxidation reactions in organic synthesis. However, application of these catalysts in aqueous solution is limited by their effectiveness and stability. In this study, a novel graphene based Schiff base copper complex (Cu(salen)) was developed to effectively activate persulfate (PS) for the removal of organic pollutants in aqueous solution. Aminated reduced graphene oxide (ArGO) was used as a carrier of the heterogeneous catalyst, DArGO-Cu, which was synthesized by the condensation reaction of 3, 5-dibromosalicylaldehyde with ArGO followed by the complexing reaction with copper acetate monohydrate. The surface structure and morphology as well as elemental composition of DArGO-Cu were characterized by SEM, TEM, XPS, FTIR, Raman and elemental analysis. The catalytic performance of DArGO-Cu to activate PS was evaluated with the degradation of triclosan (TCS) in water at room temperature. The mechanism for DArGO-Cu to activate PS was the generation of SO4− which was immediately converted to OH to degrade TCS. The role of graphene played in catalysis was not only as a carrier for Cu(salen) but also to build hydrophobic microdomains for the stabilization of the catalytic active sites in the reaction.

Bioconversion of toxic micropollutant triclosan to 2,4-dichlorophenol using a wastewater isolate Pseudomonas aeruginosa KS2002

Triclosan, a commonly available pesticide, has emerged as a ubiquitous pollutant posing a major threat to the environment. Here we have isolated a wastewater microorganism, Pseudomonas aeruginosa KS2002, capable of converting triclosan to 2,4-dichlorophenol within 96 h of incubation. The confirmation of the end product was done using Fourier transform infrared spectroscopy and mass spectroscopy. Different minimal media were investigated to establish a suitable media supporting maximum triclosan degradation. Spectral analysis showed that this bacterial isolate degraded 99.89% ± 0.3 of 2 g/L of triclosan spiked in an M9 minimal salt medium. This isolate utilized fructose and glycerol as a co-substrate to enhance degradation process. The cell-free extract of Pseudomonas aeruginosa KS2002 showed the activity of catechol 2,3-dioxygenase enzyme (specific enzyme activity = 0.161 U/mg). In the presence of 3-fluorocatechol, a meta-cleavage enzyme inhibitor, triclosan degradation was ceased suggesting a meta-cleavage pathway for triclosan degradation. Keeping in view the observations recorded, we proposed a pathway for partial triclosan degradation using this isolate.

Experiments and numerical simulation on the degradation processes of carbamazepine and triclosan in surface water: A case study for the Shahe Stream, South China

We examined the occurrence and fate of pharmaceuticals and personal care products in surface water by combining laboratory experiments with numerical simulations. The degradation processes of two typical PPCPs (triclosan and carbamazepine) collected from the Shahe Stream were studied. Hydrolysis, biodegradation, and photolysis were the three major routes of triclosan (TCS) and carbamazepine (CBZ) degradation. A central composite design method was used to investigate the effects of related natural parameters (including pH, dissolved oxygen, salinity, temperature, light intensity, and humic acid) on the TCS and CBZ degradation processes in the laboratory. Our results showed that the main degradation pathway of CBZ and TCS was direct photolysis during the daytime and that the maximal biodegradation rates of CBZ and TCS occurred at 22 °C when the optimum temperature function was used. Based on our experimental results, the observed degradation of CBZ and TCS followed pseudo-first-order kinetics, and the degradation kinetic equations under the influence of multiple natural parameters were established with estimated average degradation rate constants of 1.2452E−7 s−1 and 3.1260E−5 s−1 for CBZ and TCS, respectively. The degradation rate constants were incorporated into a one-dimensional, simply integrated hydrodynamic and water quality model. The proposed numerical model was applied to depict the transportation and transformation of CBZ and TCS in surface water and was validated by observational data from the Shahe Stream. The results showed that our model reproduced the observed patterns of CBZ and TCS concentrations reasonably, with slight overestimations compared to the observed data; the relative errors between the simulated and the observed concentrations were 5.85%–6.82% for CBZ and −156.85%–−7.18% for TCS. According to our simulation, the spatial distribution of TCS in surface water was determined by biochemical degradation processes that were most affected by temperature under natural conditions; in contrast, the distribution of CBZ was largely controlled by diffusion.

Degradation of Triclosan and Carbamazepine in Two Agricultural and Garden Soils with Different Textures Amended with Composted Sewage Sludge.

Composted sewage sludge (CSS) has been extensively used in agriculture and landscaping, offering a practical solution for waste disposal. However, some pharmaceutical and personal care products (PPCPs) like triclosan (TCS) and carbamazepine (CBZ) have restricted its land application. In this study, CSS was added to agricultural soil and garden soil at 0%, 5%, 10%, and 25% (w/w soil), and 4 mL of TCS and CBZ stock solution (1000 mg/L in methanol) was spiked into soil amended with CSS of each bottle to arrive at the concentration of 10 mg/kg. Samples were then collected after incubation for 120 days and analyzed for concentrations and half-life (t1/2) of TCS and CBZ, and soil physicochemical properties, together with enzyme activities. The results showed that TCS was degraded completely during the incubation period. In contrast, only about 5.82–21.43% CBZ was degraded. CSS amendment inhibited TCS and CBZ degradation and prolonged t1/2 compared to the control, and the t1/2 of TCS and CBZ increased with CSS addition amount in all treatments except for CBZ in the garden soil amended with 10% CSS. Correlation studies showed a significantly positive relationship between t1/2 of TCS and CBZ and total organic carbon (TOC), while a significantly negative relationship between t1/2 of the two PPCPs and pH was observed. Alkaline phosphatase showed a significantly negative relationship with the Ct/C0 of TCS in garden soil amended with 25% CSS and CBZ in the control. The urease activity was negatively correlated with the Ct/C0 of TCS in 10% and 25% CSS treatments and CBZ in 10% CSS treatment for garden soil.

Photo-catalytic degradation of triclosan with UV/iodide/ZnO process: Performance, kinetic, degradation pathway, energy consumption and toxicology

This study develops UV/Iodide/ZnO (UIZ) photo reactor to employs it for degradation, dechlorination and mineralization of triclosan (TCS) content of wastewaters. Degradation efficiency of the UV-only, UV/ZnO, UV/Iodide and UIZ processes were determined as 12.3%, 37.3%, 50.43% and 89.83% respectively, at 20 min reaction time, 10 mg L−1 TCS concentration and pH of 7. Findings indicated that the TCS completely degraded within 20 min treatment time. According to Weight ratio evaluations, the 1.26:2:10 ration is the optimal Weight ratio of Iodide /ZnO/TCS in the UIZ process. Analyzing effluents of the UIZ reactor by liquid chromatography/mass spectroscopy after 5, 10, 15 and 20 min reaction time revealed that TCS decomposes to ring-shaped compounds in less than 10 min and all TCS and its metabolites convert to linear compounds within 15 min reaction time. Investigating kinetic of the process through a pseudo first-order model using 1 to 10 mg L−1 TCS over 1 to 15 min reaction time demonstrated that the observed rate constant (kobs) decreases from 0.3405 to 0.0687 min−1 and the observed TCS degradation rate (robs) increases from 3.405 to 13.74 mg L−1 min−1 with increasing the TCS concentration. Furthermore, electrical energy consumption (EEO) of the UIZ process was calculated with kinetic model 2.48 to 12.29 and with merit-figure model 2.87 (2.87–8.95) to 14.88 (14.88–33.02) kW h m−3 from 1 to 10 mg L−1, respectively. In addition, the effect of co-existing water anions on degradation of 10 mg L−1 TCS was explored during 20 min processing. While 100% degradation was achieved in the absence of any anion, adding nitrate, as the most effective anion, decreased the TCS degradation to 72.88%. The highest dechlorination was observed at Iodide/ZnO weight ratio 1.26:1 and pH 9. Mineralization of TCS by UIZ process was achieved 38.6% after 15 min reaction time. In presence of the effluents extracted after 10 min TCS degradation (even after long incubation periods), no growth inhibition was observed using Analysis of the effluent dilution effect and toxicity assessment on Escherichia coli. Finally, feeding effluents of the UIZ photoreactor to cyclic rotating-bed biological reactor (CRBR) helped to reduce COD nearly completely after 1.5 h aeration, respectively. Therefore, the proposed UIZ/CRBR process is a promising technology for efficient treatment of the wastewaters containing TCS.

Enhanced photocatalytic performance of zinc oxide nanostructures via photoirradiation hybridisation with graphene oxide for the degradation of triclosan under visible light: Synthesis, characterisation and mechanistic study

Modification of ZnO nanoparticles with graphene oxide (GO) was carried out, and the obtained hybrid photocatalyst was used for the photodegradation of triclosan (TCS), which is an endocrine disrupting compound. Three different concentrations of GO were used to modify ZnO catalyst using the photoirradiation method and the resultant materials were characterised by SEM, TEM, Zeta Potential, FTIR, Raman, N2 Physisorption, HPLC, XRD and UV–vis spectrophotometry in order to determine their physico-chemical and photocatalytic properties. Regarding the photocatalytic evaluation, the results of the photodegradation process for TCS showed that GO acts as a trap of electrons improving the performance of ZnO even at low TCS concentration (8 mg.L−1) under visible light radiation. The GO-modified composite that contains the highest GO concentration (0.5% w/w) was the material that showed the best photocatalytic performance under visible light degrading up to 45% of the initial concentration of TCS and showed a reaction rate constant two times higher than pristine zinc oxide. This study allowed us to propose the photocatalytic mechanism of ZnO/GO hybrid photocatalysts to degrade TCS. In addition, this research contributes to the understanding of the enhancement of the efficiency of ZnO/GO hybrids and contributes to obtaining a photoactive material with promising use under natural light radiation in an Advance Oxidation Process to eliminate endocrine-disrupting compounds such as triclosan.

Activation of peroxymonosulfate by sludge-derived biochar for the degradation of triclosan in water and wastewater

In this study, a sludge-derived biochar (SBC) was prepared, characterized and applied to activate peroxymonosulfate (PMS) for the degradation of triclosan (TCS) in water and wastewater. The results showed that SBC had porous structure with specific surface area of 157.4 m2 g−1. The optimal conditions for TCS degradation were examined as follows: pH 7.2, biochar dosage of 1.0 g/L and PMS concentration of 0.8 mM at 25 °C. The removal efficiency of total organic carbon (TOC) reached 32.5% within 240 min under optimal conditions. Hydroxyl radicals, sulfate radicals and singlet oxygen contributed to TCS degradation. Dechlorination and hydroxylation were the main pathway of TCS degradation. Based on the intermediate products detected during the TCS degradation, the degradation pathway of TCS was tentatively proposed. This study demonstrated that SBC could be an effective activator of PMS for the degradation of toxic organic pollutants in water and wastewater.

Dechlorination of triclosan by enhanced atomic hydrogen-mediated electrochemical reduction: Kinetics, mechanism, and toxicity assessment

Environmental-friendly and efficient technologies for the removal of halogenated organic compounds in water are highly desired. Triclosan (TCS) is a potential threat to the environment and human health, and is resistant to biodegradation. Here, a Pd/N-GR/Cu foam exhibits a much enhanced activity as the cathode for TCS degradation by electrochemical reduction. The dechlorination rate of Pd/N-GR/Cu foam is 5.50, 6.49, and 14.68 times higher than Pd/Cu, N-GR/Cu, and Cu foam, respectively. The leaching of Pd and Cu is inhibited due to the protection by cathodic currents and alkaline conditions. 2- and 1-chlorinated isomers are the main intermediates, and the final products are completely dechlorinated 2-phenoxyphenol with a small amount of further H radical addition product 6-phenoxycyclohex-3-enol. ESR spin trapping results indicate the coupling of Pd and N-GR promotes the production and utilization of atomic H*, and the contribution of atomic H* obeys the order of Pd/N-GR/Cu (68.5%) > Pd/Cu (56.6%) > N-GR/Cu (24.3%) > Cu (5.7%). The bacterial cytotoxicity and AhR activity of TCS solution after 60 min are decreased by 83.2% and 90.3%, respectively. The electrochemical reduction can be a promising option for supplementing the current technologies for TCS abatement in wastewater.

Biochar does not attenuate triclosan's impact on soil bacterial communities

Triclosan, a broad-spectrum antimicrobial, has been widely used in pharmaceutical and personal care products. It undergoes limited degradation during wastewater treatment and is present in biosolids, most of which are land applied in the United States. This study assessed the impact of triclosan (0–100 mg kg−1) with and without biochar on soil bacterial communities. Very little 14C-triclosan was mineralized to 14CO2 (<7%) over the course of the study (42 days). While biochar (1%) significantly lowered mineralization of triclosan, analysis of 16S rRNA gene sequences revealed that biochar impacted very few OTUs and did not alter the overall structure of the community. Triclosan, on the other hand, significantly affected bacterial diversity and community structure (alpha diversity, ANOVA, p < 0.001; beta diversity, AMOVA, p < 0.01). Dirichlet multinomial mixtures (DMM) modeling and complete linkage clustering (CLC) revealed a dose-dependent impact of triclosan. Non-Parametric Metastats (NPM) analysis showed that 150 of 734 OTUs from seven main phyla were significantly impacted by triclosan (adjusted p < 0.05). Genera harboring opportunistic pathogens such as Flavobacterium were enriched in the presence of triclosan, as was Stenotrophomonas. The latter has previously been implicated in triclosan degradation via stable isotope probing. Surprisingly, Sphingomonads, which include well-characterized triclosan degraders were negatively impacted by even low doses of triclosan. Analyses of published genomes showed that triclosan resistance determinants were rare in Sphingomonads which may explain why they were negatively impacted by triclosan in our soil.

Occurrence, degradation and potential ecological risks of triclosan in environment.

Triclosan (TCS) is widely used in many kinds of personal care products due to its good antibacterial properties. However, TCS can enter environment in many ways through the consumption of those personal care products, and result in a series of environmental problem. TCS and its metabolites have their own characteristics such as environmental persistence, bioaccumulation and ecological toxicity, which may bring some potential risks to the ecosystem and human health. We summarized the occurrence and distribution characteristics of TCS in the environment, as well as the possible degradation pathways and products. Furthermore, we systemically introduced the bioavai-lability and the ecotoxicological effects of TCS and its metabolites on the reproduction and genetics of organism, and their potential risks to the ecosystem and human health. Finally, we proposed brief suggestions for further studies of TCS.

Accumulation and sublethal effects of triclosan and its transformation product methyl-triclosan in the earthworm Eisenia andrei exposed to environmental concentrations in an artificial soil.

Municipal biosolids are increasingly used as a low-cost fertilizer in agricultural soil. Biosolids are contaminated by low concentrations (nanograms per gram dry wt range) of a large variety of organic contaminants, such as triclosan. The effect of exposure to low concentrations of organic contaminants on soil biota remains largely undocumented. We evaluated the sublethal effects of triclosan on the earthworm Eisenia andrei using an artificial soil amended with a nominal concentration of triclosan of 50 ng g-1 dry weight soil. Using a 56-d reproduction test, we monitored the effect of triclosan exposure on adult earthworm survival, growth, and reproduction. The bioaccumulation of triclosan in earthworm tissue (adults and juveniles) and degradation of triclosan were monitored. The genotoxicity of triclosan was evaluated using a comet assay (DNA damage) on adult earthworm coelomocytes. Exposure to a low concentration of triclosan had no significant effects on adult earthworm survival and DNA damage but significantly stimulated growth (p < 0.05) by 2-fold compared with controls. It also significantly affected E. andrei reproduction parameters (p < 0.05), as evidenced by an increase in the number of cocoons and juveniles and a decrease in the mean dry weight of juveniles. The bioaccumulation of triclosan in earthworms was moderate (bioaccumulation factor ∼2). In biosolid-borne trials, the bioaccumulation of methyl-triclosan in earthworm tissues was higher than that of the parent compound triclosan. We conclude that exposure to low concentrations of triclosan in artificial soil can significantly affect the growth and reproductive performance of earthworms (i.e., E. andrei). More research is required with natural soils to assess triclosan bioavailability for earthworms. Environ Toxicol Chem 2018;37:1940-1948. © 2018 SETAC.

Degradation of triclosan by chlorine dioxide: Reaction mechanism,2,4-dichlorophenol accumulation and toxicity evaluation

The mechanism and toxicity of TCS degradation by ClO2 was investigated. Intermediate products during the oxidation process were identified by GC/MS and LC/MS. A microtox bioassay and a SOS/umu assay were employed to evaluate the acute toxicity and genotoxicity of the resulting solutions during the chlorination process. The results showed that the reaction between TCS and ClO2 was of second-order overall. The pseudo first-order rate constants (kobs) exhibited significant dependence on solution pH and chlorine dioxide concentration, with the apparent second-order rate constant, kapp, being 7.07 × 104 M−1s−1 in the pH range of 6.80–7.02. TCS decomposition was accompanied by the accumulation of 2,4-dichlorophenol (2,4-DCP), and the maximum molar yield ratios of 2,4-DCP/TCS were in the range of 31.71%–35.43%. The major intermediates identified were 2,7/2,8-dichlorodibenzop-dioxin (2,7/2.8-Cl2DD), 2,4-DCP, 2,4,6-trichlorophenol (2,4,6-TCP), tetraclosan and pentaclosan. The proposed mechanism for TCS oxidation involved the cleavage of the ether link in TCS, chlorination of the phenolic ring and ring closure of a single TCS molecule. The transformation and degradation of TCS led to reduction of the acute toxicity and genotoxicity. However, irregular fluctuations in the toxicity changes indicated that the oxidation of TCS was not a simultaneous detoxification process.

Nanocomposite Au NP/TiO2 thin film in the efficient remediation of aqueous solutions contaminated with emerging micro-pollutants.

The present communication specifically aims to synthesize novel nanocomposite material Au NPs/TiO2 in a simple template process using the polyethylene glycol as filler media. The thin film of the nanocomposite material was characterized by the advanced analytical tools. The surface morphology was obtained by the scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images of solids. Similarly, the surface topography and roughness of solid were obtained by the atomic force microscopic (AFM) image of thin film. X-ray diffraction (XRD) data enabled to confirm that the TiO2 was predominantly present with its anatase phase. The specific surface area and pore size of the solid were obtained using the N2 adsorption/desorption data. Nanocomposite Au NP/TiO2 thin film was employed in the photocatalytic removal of sulfamethoxazole and triclosan from aqueous solutions using less harmful UV-A light (λmax = 330nm). Various physicochemical parametric studies enabled to deduce the mechanism involved in the degradation process. The degradation kinetics as a function of pH (pH 4.0-10.0) and micro-pollutant concentrations (0.5-15.0mg/L) was extensively studied. The mineralization of these pollutants was obtained using the non-purgeable organic carbon (NPOC) data. The stability of thin film was assessed by the repeated operations, and presence of several co-existing ions simulates the studies to real matrix treatment. Further, the presence of scavengers enabled to pin point the radical-induced degradation of sulfamethoxazole and triclosan from aqueous solutions.

Degradation of triclosan by environmental microbial consortia and by axenic cultures of microorganisms with concerns to wastewater treatment.

Triclosan is an antimicrobial agent, which is widely used in personal care products including toothpaste, soaps, deodorants, plastics, and cosmetics. Widespread use of triclosan has resulted in its release into wastewater, surface water, and soils and has received considerable attention in the recent years. It has been reported that triclosan is detected in various environmental compartments. Toxicity studies have suggested its potential environmental impacts, especially to aquatic ecosystems. To date, removal of triclosan has attracted rising attention and biodegradation of triclosan in different systems, such as axenic cultures of microorganisms, full-scale WWTPs, activated sludge, sludge treatment systems, sludge-amended soils, and sediments has been described. In this study, an extensive literature survey was undertaken, to present the current knowledge of the biodegradation behavior of triclosan and highlights the removal and transformation processes to help understand and predict the environmental fate of triclosan. Experiments at from lab-scale to full-scale field studies are shown and discussed.

Degradation of Triclosan by Heat Activated Persulfate Oxidation

Sulfate radical (SO4·-)-based advanced oxidation technologies (SR-AOPs) are widely used for remediation of contaminated groundwater and soils. This study investigated the reaction kinetics, products, and transformation pathways of triclosan, a widely used antimicrobial agent, during its degradation by heat activated persulfate oxidation. Experimental results revealed that increasing temperature or initial persulfate concentration significantly enhanced the degradation of triclosan. The reaction could be fitted in the pseudo-first-order kinetic model and the activation energy (Ea) was determined to be 142 kJ·mol-1. The presence of humic acid markedly inhibited triclosan degradation, whereas chloride (Cl-) showed a more complicated effect. Triclosan degradation was slightly accelerated in the presence of 5 μmol·L-1 Cl-, however, a higher concentration of Cl- (e.g., 10 μmol·L-1) showed an inhibitory effect. Using liquid chromatography-mass spectrometry, a total of six transformation products, including 4-chlorocatechol, 2,4-dichlorophenol, and 2-chloro-5-(2,4-dichloro-6-hydroxyphenoxy)-1,4-benzoquinone, were identified. Accordingly, the cleavage of the ether bond and hydroxylation of the phenol ring were proposed as the principal pathways of triclosan degradation upon reaction with SO4·-. The findings of this study can be used to evaluate the feasibility of decontamination of triclosan by SR-AOPs.