Degradation Of Triclosan Research Articles

Enhanced degradation of triclosan using UV–Fe2+synergistic activation of peracetic acid

UV/Fe2+/peracetic acid (PAA) as an efficient and novel advanced oxidation system was reported to produce reactive species (i.e., hydroxyl radicals (˙OH) and organic radicals) for triclosan (TCS) degradation.

Synergistic degradation of triclosan from aqueous solution by combination of sulfate radical and electrocoagulation process

Synergistic degradation of triclosan from aqueous solution by combination of sulfate radical and electrocoagulation process

Coatings of magnetic composites of iron oxide and carbon nitride for photocatalytic water purification.

Magnetic composites of iron oxide (α-Fe2O3 and Fe3O4) and carbon nitride materials (CN) were synthesized via a microwave assisted hydrothermal method starting from iron salts and CN, which was obtained by thermal decomposition of dicyandiamide. The as-prepared composites with iron oxide loadings of 0.5 ω%–6 ω% were characterized by powder X-ray diffraction (PXRD), diffuse reflectance UV-vis spectroscopy, magnetization measurements, nitrogen adsorption measurements and thermogravimetric analyzes (TGA). The composites were examined for the degradation rate of an aqueous rhodamine B (RhB) solution under visible light irradiation. The magnetic composite α-Fe2O3(3 ω%)/CN enables 82% degradation of RhB within 90 min. Therefore, this material was selected for an immobilization approach and deposited using a spray coating technique on a magnetic polymer substrate. Coatings with loadings from 1.1 mg to 3.6 mg were compared with regard to their activity for the photocatalytic degradation of RhB under visible light irradiation. The substrate loaded with 0.4 mg cm−2 catalyst enables a RhB degradation of 61% within 8 h. Photocatalytic degradation of triclosan and ethinyl estradiol was also successful and both compounds were degraded with up to 46% of the initial concentration within 8 h. ICP-MS measurements of the pollutant solutions after photocatalytic treatment showed that leaching does not occur.

Influence of the type of photocatalyst on photocatalytic oxidation of triclosan in the aquatic environment

A comparative assessment of triclosan removal (an antibacterial compound) in aqueous solutions at a concentration of 1.0 mg/dm3 during an advanced oxidation process in the presence of commercial titanium dioxide (TiO2) and photocatalysts modified with the powdered activated carbon and ultrasounds was studied. Photocatalytic processes were examined using a photocatalyst at the dose concentration of 100 mg/dm3. The influence of photocatalysts modification on triclosan sorption process and its decomposition was found. Triclosan was adsorbed in the range of 69% to 96%. After 20 minutes of the photocatalysis, triclosan decomposition was set to 91% in the presence of pure TiO2. For the modified photocatalysts, the removal degree exceeded 99% after 10 minutes of irradiation. The Langmuir-Hinshelwood model was used to describe the kinetics of triclosan degradation. Reaction kinetics showed a two-stage oxidation process in the presence of a photocatalyst modified with activated carbon and ultrasounds.

Flexible reusable hierarchical hybrid catalyst for rapid and complete degradation of triclosan in water

A flexible, durable, and reusable nanocatalyst system was fabricated by anchoring palladium nanoparticles on carbon nanotube (CNT) carpets covalently attached to carbon cloth. These hierarchical hybrid materials were tested for catalytic degradation of triclosan (TCS), an emerging contaminant. Materials were characterized using scanning & transmission electron microscopy techniques (SEM and TEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). The reaction kinetics was studied using HPLC and reaction pathways proposed based on LC-MS/GC-MS analyses. In the presence of hydrogen, complete step-wise chlorine removal was seen until complete dechlorination was accomplished. The pseudo-first-order rate constant was measured to be orders of magnitude higher than earlier reported values. Moreover, the same material was usable for multiple cycles in flowing water. This study demonstrates that robustness and reusability of larger structural materials can be combined with the ultra-high surface activity of nanocatalysts to provide practical and eco-friendly solutions for water sustainability.

Enhanced degradation of triclosan by gamma radiation with addition of persulfate

In this study, gamma radiation was used for triclosan (TCS) degradation with addition of persulfate (PS) to enhance the mineralization of TCS. The influence of absorbed doses, PS concentration, and initial pH value on TCS degradation and mineralization was examined. The results showed that the degradation and mineralization of TCS were remarkably enhanced in the presence of PS. With addition of 1.5 mM PS, 8 mg/L TCS could be completely degraded at 300 Gy, which was much lower than that of the control group without PS (600 Gy). Furthermore, with addition of PS, higher mineralziaiton of TCS could be observed. The intermediates produced during the decomposition of TCS were identified and the possible degradation pathway was proposed. In addition, the biodegradability of TCS solution, as well as the intermediate products, was evaluated by a Wabo micro-respiration tester for 12 h. It demonstrated that the biodegradability of TCS solution increased after gamma radiation, which could be further enhanced by persulfate, suggesting that the combination of gamma radaition with persulfate could be a promising alternative process for the degradation of antibiotics in the wastewater.

Linking Triclosan's Structural Features to Its Environmental Fate and Photoproducts.

Triclosan is a high-production volume chemical, which has become widely detected in environmental systems because of its widespread usage. Photodegradation has been identified as a major degradation pathway, but the identified photoproducts are also chemicals of concern. In this study, lower chlorinated derivatives of triclosan were synthesized to investigate the impact the chlorine substituents have on the photodegradation rate and the photoproducts produced. In addition, the photodegradation of two classes of photoproducts-dibenzo-p-dioxins (DDs) and 2,2'-dihydroxylated biphenyls-was also investigated. Degradation of triclosan in near-surface sunlit waters was relatively fast (t1/2 < 5 h). Calculated degradation rates were slower for DDs and faster for dihydroxylated biphenyls in comparison to that for triclosan. In addition, the 2'-Cl substituent was critical for the high quantum yield measured for triclosan and necessary for the photodegradation mechanism that forms DDs and dihydroxylated biphenyls. The 4-Cl substituent was responsible for higher rates of light absorption and the environmentally relevant pKa. Without either of these substituents, the environmental fate of triclosan would be markedly different.

Insights into the photocatalytic degradation of triclosan over amorphous Nb2O5 catalysts

Photocatalytic degradation of triclosan is one of the most promising way to eliminate triclosan pollution in water, yet it presents profound challenges to develop efficient photocatalysts to meet the demand of application. Herein, we demonstrate a facile hydrothermal-precipitation method to prepare amorphous Nb2O5 catalysts by using niobium(V) oxalate hydrate and ammonium carbonate. A series of amorphous Nb2O5 catalysts were obtained and analyzed by detail characterizations (XRD, XPS, BET and SEM). By optimizing synthesis conditions, it was found that 180/12-Nb2O5-(1:5) catalyst exhibited the optimal photocatalytic activity for triclosan degradation. Furthermore, the pseudo-first-order kinetic equations for triclosan degradation over 180/12-Nb2O5-(1:5) catalyst were investigated under conditions with different pH value. Among them, the triclosan degradation rate over 180/12-Nb2O5-(1:5) catalyst gave the highest reaction constant k (0.5 min−1) and shortest half-period (t1/2 = 0.17 min−1) at pH of 8. The presence of ionic state triclosan in base condition should be responsible for the improved degradation rate from acid to base reaction condition. Compared with molecular triclosan, ionic state triclosan exhibits very high reaction rate with radicals due to its strong electrophilic property. The high photocatalytic activity of 180/12-Nb2O5-(1:5) catalyst should be related to the presence of amorphous structure compared with calcined 180/12-Nb2O5-(1:5) catalyst with highly crystalline structure. The existence of N species doping and nano-sheet structure in catalyst is also thought to promote the catalytic reaction.

Ferrous-activated persulfate oxidation of triclosan in soil and groundwater: The roles of natural mineral and organic matter

Contamination of antimicrobial agents such as Triclosan (TCS) in soil and groundwater possess high risk to human health and ecological systems. Present study systematically studied the degradation of TCS in soil and groundwater by Fe2+ activated persulfate (Fe2+/PS) oxidation process and special attention was paid on revealing the influence of remediation process on soil physicochemical and microbial characteristics. Experimental results demonstrated that TCS was readily degraded in soil upon Fe2+/PS oxidation system. Higher Fe2+/PS concentration and lower pH value may promote the TCS degradation. Besides added Fe2+, the naturally present Fe (III)-O and dissolved Fe from iron containing minerals may also activate PS for TCS degradation. SO4•−, HO•, R• and 1O2 were identified to be involved in the reaction system while addition of Fe2+-chelating agents, e.g., oxalic acid and ethylene diamine tetraacetic acid (EDTA) may slightly promote the degradation. Low concentration of Cl− facilitated TCS degradation and high concentration of Cl− slowed down the degradation. The presence of HCO3− may inhibit the degradation. Fe2+/PS oxidation process may partly reduce the soil organic matter content and diversely affect the composition of various C functional groups on soil. It also induced the breakdown of large soil aggregates and reduced the soil porosity, especially at macroporosity region. Phospholipid Fatty Acid test indicated that soil microbial community structure has been altered and the actinomycetes, fungi and Gram-negative bacteria decreased largely. The feasibility of remediation of TCS using Fe2+/PS oxidation in various natural groundwater samples was evaluated. Finally, five degradation intermediates of TCS by Fe2+/PS oxidation in soil were enriched by solid phase extraction and were identified by liquid chromatography-triple quadrupole mass spectrometry for proposing detailed transformation pathways.

Insights into the electrochemical degradation of triclosan from human urine: Kinetics, mechanism and toxicity

Electrochemical degradation of triclosan in human urine was firstly studied by using Ti/SnO2–Sb/PbO2 anode doped with rare-earth elements. The results indicated that the Ti/SnO2–Sb/Gd-PbO2 anode demonstrated the best performance with the degradation rate constants being 0.095 min−1 in fresh urine and 0.045 min−1 in hydrolyzed urine at a current density of 10 mA cm−2. The electrochemical degradation was improved in the presence of phosphate and chloride, while the degradation was obviously inhibited by urea, bicarbonate and ammonia. Degradation mechanism mainly involved ether-bond cleavage, hydroxylation, cyclization, dehydrogenation and carboxylation. Quantitative structure-activity relationship model showed that ecological risks of cyclization products to fish, daphnid and green algae was higher than the parent compound, implying that the potential risks to aquatic organism should not be ignored before triclosan mineralized completely. Energy consumption for 90% triclosan degradation ranged from 4.5 to 47.8 Wh L−1, and the consumption increased along with the hydrolysis of urine. The results indicate that electrochemical oxidation is a feasible and energy-saving technique to effectively remove triclosan from human urine.

Metagenomics combined with DNA-based stable isotope probing provide comprehensive insights of active triclosan-degrading bacteria in wastewater treatment

The biotransformation of triclosan (TCS) during wastewater treatment occurred frequently, while little researches are known the identity of microorganisms involved in the biodegradation process. In this work, DNA-based stable isotope probing (DNA-SIP) was occupied to investigate the TCS assimilation microbes originated from a full-scale cyclic activated sludge system in Beijing. Results of TCS removal pathway showed that the TCS removal in nitrification process was mainly contributed by the metabolism of heterotrophic bacteria, accounting for about 18.54%. DNA-SIP assay indicated that Sphingobium dominated the degradation of TCS. Oligotyping analysis further indicated that oligotype GCTAAT and ATGTTA of Sphingobium played important roles in degrading TCS. Furthermore, the Kyoto Encyclopedia of Genes and Genomes functional abundance statistics based on PICRUSt2 showed that glutathione transferase was the most prevalent enzyme involved in TCS metabolism, and TCS might be removed through microbial carbon metabolism. Metagenomics made clear that Sphingobium might play irrelevant role on the propagation of antibiotics resistance genes (ARGs), even though, it could degrade TCS. Thauera and Dechloromonas were identified as the key hosts of most ARGs. This study revealed the potential metabolic pathway and microbial ecology of TCS biodegradation in nitrification process of wastewater treatment system.

Continuous process applied to degradation of triclosan and 2.8-dichlorodibenzene-p-dioxin.

This study describes the use of a prototype for the continuous photocatalytic reaction process using Fe/Nb2O5-immobilized catalyst for triclosan and 2.8-dichlorodibenzene-p-dioxin (2.8-DCDD)'s degradation. The experiments were carried out with different parameters and matrices in a steady state. In addition, photolysis and photocatalytic tests were performed. The results indicated that the generation of 2.8-DCDD was observed in matrices with Cl-. The Fe/Nb2O5-immobilized catalysts were efficient in the degradation of triclosan and 2.8-dichlorodibenzene-p-dioxin. However, 2.8-DCDD formation was not observed in the ultra-pure water matrix, which indicated influence of ions. The photocatalysis was more efficient than the photolysis when comparing both matrices and radiation. Even with a radiation oscillation, the solar process showed positive results.

Rapid destruction of triclosan by Iron(III)-Tetraamidomacrocyclic ligand/hydrogen peroxide system

Iron(III)-tetraamidomacrocyclic ligand (Fe(III)-TAML) activators can activate hydrogen peroxide to oxidize many kinds of organic pollutants. In this study, we investigated the degradation of triclosan, a widely used broad-spectrum bactericide, under the treatment of Fe(III)-TAML/H2O2 system at different pH conditions. We also studied the influence of natural organic matter (NOM) on the degradation process. Our results showed that complete removal of triclosan could be obtained within several minutes under the optimal conditions. The degradation of triclosan by Fe(III)-TAML/H2O2 system exhibited strong pH-dependence and the degradation rate increased with the increase in pH level from 7.0 to 10.0. When adding fulvic acid (FA) or humic acid (HA) in the reaction system, the degradation of triclosan could be suppressed slightly, and HA exhibited stronger inhibition than FA. Based on the analysis of reaction intermediates, phenoxyl radical reaction and ring open reaction were involved in the decomposition of triclosan. Significant inhibition of overall toxicity to Photobacterium phosphoreum further confirmed the high efficiency of Fe(III)-TAML/H2O2 system for the removal of antibiotic activities resulting from the parent triclosan molecule and its degradation products.

Photocatalytic degradation of triclosan by oxygen defected CuO thin film

CuO thin films with oxygen defects (oxygen vacancy and oxygen excess) were prepared by sputter deposition from stochiometric CuO target. Presence of Oxygen defects was confirmed by X-ray photoelectron spectroscopy. Effect of oxygen vacancy and excess on the photocatalytic activity (Triclosan (TS) degradation) of CuO thin films under sunlight irradiation was investigated. Generation of oxygen vacancy (lower than optimum concentration) and excess considerably improved the thin film photocatalytic activity. In original work, the photocatalytic activity of the samples with oxygen vacancy was compared to the ones with oxygen excess. Moreover, the durability of the samples (oxygen vacancy and excess) after several cycles was investigated. The samples with oxygen excess showed better photocatalytic activity; though, the durability of samples with oxygen vacancy was significantly superior to the ones with oxygen excess after 5 cycles.

Fate and impact of pharmaceuticals and personal care products during septage co-composting using an in-vessel composter

The present study aimed at understanding the impact of pharmaceutical and personal care product (PPCP) load on compost dynamics and fate of PPCPs during the composting. In addition, the compost dynamics during single PPCP degradation and multiple PPCPs degradation were investigated. Results revealed that co-composting could degrade the pharmaceutical, carbamazepine (CBZ) up to 83% during single pollutant degradation while it was 66% during multiple pollutant system, at an initial concentration (IC) of 5 mg/kg dw. In case of personal care product, namely triclosan (TCS), single pollutant degradation resulted in 86% removal whereas the removal efficiency was 83% in multiple pollutant system. Relatively high concentration of CBZ showed a negative impact on compost dynamics compared to that of TCS. Higher IC resulted in lower temperature development and relatively lower pollutant removal. The study on pollutant transfer in compost solid surface and in leachate revealed that TCS was not leached out while the leaching of CBZ was significant during composting process. The various transformation products formed during composting were identified and tentative pathways for CBZ and TCS degradation were proposed.

Tracking photodegradation products and bond-cleavage reaction pathways of triclosan using ultra-high resolution mass spectrometry and stable carbon isotope analysis

Triclosan (TCS) is an antimicrobial compound ubiquitously found in surface waters throughout the world. Although several studies have focused on the photochemical degradation of TCS, there is still limited knowledge about its environmental fate. In this study, we got molecular-level insights into the photochemical degradation of TCS. Significant stable carbon isotope fractionation was observed during photodegradation; different bond-cleavage reaction pathways under different photolytic conditions were characterized, using compound specific isotope analysis (CSIA). Photochemical modeling of TCS photodegradation showed that direct photolysis would be the main transformation pathway if pH > 7, even in presence of dissolved organic matter. Moreover, by use of ultrahigh resolution mass spectrometry, FT-ICR-MS, a broad and complex spectrum of organic by-products (some of which potentially toxic, as assessed by a quantitative structure-activity relationship approach) were identified. A detailed reaction mechanism was developed on the basis of the detected compounds. A possible sequence of steps leading to some of the detected product compounds in aqueous solution is suggested.

A comparative study of UV/H2O2 and UV/PDS for the degradation of micro-pollutants: kinetics and effect of water matrix.

Organic micro-pollutants such as pesticides and endocrine disruptors cause serious harm to human health and aquatic ecosystem. In this study, the potential degradation of atrazine (ATZ), triclosan (TCS), and 2,4,6-trichloroanisole (TCA) by UV-activated peroxydisulfate (UV/PDS) and UV-activated H2O2 (UV/H2O2) processes were evaluated under different conditions. Results showed that UV/PDS process was more effective than UV/H2O2 under the same conditions. Increasing oxidant dosage or decreasing the initial ATZ, TCS, and TCA concentrations promoted the degradation rates of these three compounds. The presence of natural organic matter (NOM) could effectively scavenge sulfate radical (SO4•-) and hydroxyl radical (HO•) and reduced the removal rates of target compounds. Degradation rates of ATZ and TCA decreased with pH increasing from 5.0 to 9.0 in UV/PDS process, while in UV/H2O2 process, the increase of solution pH had little effect on ATZ and TCA degradation. In the UV/PDS and UV/H2O2 oxidation process, when the solution pH increased from 5 to 8, the removal rates of TCS decreased by 19% and 1%, while when the solution pH increased to 9, the degradation rates of TCS increased by 23% and 17%. CO32-/HCO3- had a small inhibitory effect on ATZ and TCA degradation by UV/H2O2 and UV/PDS processes but promoted the degradation of TCS significantly (> 2mM). Cl- had little effect on the degradation of ATZ, TCA, and TCS in UV/H2O2 process. Cl- significant inhibited on the degradation of ATZ and TCS, but the influence of Cl- on the degradation of TCA was weak in UV/PDS process. Based on these experimental results, the various contributions of those secondary radicals (i.e., carbonate radical, chlorine radical) were discussed. This study can contribute to better understand the reactivities when UV/PDS and UV/H2O2 are applied for the treatment of micro-pollutant-containing waters.

Facile synthesis and photocatalytic efficacy of UiO-66/CdIn2S4 nanocomposites with flowerlike 3D-microspheres towards aqueous phase decontamination of triclosan and H2 evolution

Construction of porous heterostructure photocatalyst material with improved surface and optoelectrical properties is a practical and effective strategy for mineralization of toxic organic pollutants and water splitting reaction under visible light irradiation. Herein, we have developed a facile hydrothermal route to prepare a series of novel UiO-66/CdIn2S4 heterojunction nanocomposite materials containing finely dispersed UiO-66 spherical nanoparticles (20−40 nm) anchored over high aspect ratio CdIn2S4 nanosheets. Comprehensive characterization of the UiO-66/CdIn2S4 nanocomposites revealed a hierarchical 3D microflower structure with enhanced surface reactive sites, better channelization of charge carriers, high resistance to charge recombination and a favorable band alignment between the two semiconductor components. The optimal photocatalyst (30UiO-66/CdIn2S4) showed improved photocatalytic efficiency towards triclosan degradation with rate constant (0.0094 min−1) twelve times higher than the pure CdIn2S4 (0.0007 min−1). The 30UiO-66/CdIn2S4 photocatalyst also exhibited higher H2 evolution rate (2.95 mmolg−1 h−1) with apparent conversion efficiency of 20.8 %.

Highly efficient photocatalytic hyperbranched polyethyleneimine/bismuth vanadate membranes for the degradation of triclosan

Worldwide, pharmaceutical and personal care products are increasingly being used and produced and their presence in various water bodies has attracted significant attention amongst the public and scientists. Classified as emerging pollutants, these pharmaceutical and personal care products ultimately accumulate in and contaminate natural water bodies through several pathways. In this study, a photocatalytic membrane consisting of bismuth vanadate nanoparticles and hyperbranched polyethyleneimine, blended in polyethersulphone, was used in the degradation of triclosan. Bismuth vanadate was characterised using X-ray diffraction and Raman spectroscopy. These analyses revealed that there was successful synthesis of the monoclinic phase of bismuth vanadate, as well as a monoclinic-to-tetragonal (M → T) phase transformation upon the addition of hyperbranched polyethyleneimine to the nanoparticles. The modified membranes showed improved water flux and hydrophilicity (contact angles of between 71° and 56°) as compared to that of the bare polyethersulphone (75°) upon the addition of hyperbranched polyethylene amine and bismuth vanadate. The modified membranes were effective in the photodegradation of triclosan (up to 86%), and the generation of chloride ions was observed.

Enhanced photocatalytic degradation of antimicrobial triclosan using rGO–TiO2 composite under natural solar illumination

In the present study, the enhancement in the photocatalytic degradation of triclosan after incorporation of reduced graphene oxide (rGO) in pristine TiO2 is investigated. Triclosan is an antimicrobial compound found in commonly used personal care products. The study involved the synthesis of reduced graphene oxide–titania composite using the improved Hummer and hydrothermal methods. The optimum rGO content in the composite was found to be 10 wt% (RT10). The composite was characterized using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, Scanning electron microscopy (SEM), and Brunauer–Emmett–Teller surface area (BETSA). The experimental conditions viz. catalyst dose, initial triclosan concentration, and solution pH were studied. The surface area of the composite was substantially higher than either of TiO2 and GO. The photocatalytic reaction followed pseudo-first-order kinetics with the highest rate constant of 0.251 h−1 obtained for RT10. The scavenging experiment indicated the role of hydroxyl radical in the degradation mechanism. The composite displayed efficient degradation under natural sunlight attributed to narrowing of band gap. It also performed effectively in secondary effluent containing triclosan despite matrix effect. Thus, the composite has potential application as a promising photocatalyst in tertiary treatment of water and wastewater.