Degradation Of Methylparaben Research Articles

Solar photocatalytic degradation of parabens using UiO-66-NH2

The photocatalytic degradation of methylparaben was investigated under simulated solar light using a synthesised metal–organic framework (UiO-66-NH2). For that purpose, the pollutant was spiked in different water matrices: distilled water, water from Lima River (Northwestern Portugal), and urban wastewater. Complete removal of the methylparaben in distilled water was achieved in 1 h reaction. In natural water matrices, the photocatalytic performance decreased to 70% removal after 3 h reaction, owing to the physical–chemical properties of the water samples. The UiO-66-NH2 photocatalyst revealed high stability under the continuous mode, reaching a steady state in 5 h, from which the removal percentage was kept constant for 25 h. The photocatalytic degradation of methylparaben gave five main reaction byproducts and four short-chain carboxylic acids, identified by LC/ESI-MS and UHPLC analyses, respectively. The mechanism of degradation was investigated by using selective scavengers. Photogenerated holes and superoxide radicals were found as the main species responsible for the degradation of methylparaben. The abatement of other parabens (as ethyl- and propylparaben) was also evaluated, being the conversion influenced by the length of the alkyl side chain. The results of this study give a comprehensive sight into the effective photocatalytic remediation of parabens using UiO-66-NH2.

RGO-induced charge transfer and hole oxidation enhanced photocatalytic degradation and disinfection performance of novel ternary nanocomposite under visible light irradiation

A novel graphene-bridged AgCl/Ag3PO4/rGO photocatalyst with admirable visible-light-driven photocatalytic performance was prepared through a combination of in-situ precipitation and anion-exchange method. The photocatalyst was revealed a well-defined heterostructure in which few-layers rGO sheets are decorated by AgCl and Ag3PO4 nanoparticles. The ternary photocatalyst exhibits excellent photocatalytic activity for the degradation of methylparaben (MPB) and the inactivation of Gram-negative Escherichia coli (E. coli) due to the synergistic effects of AgCl, Ag3PO4 and rGO. Results show that 20 mg•L−1 of MPB or 107 CFU•mL−1 of E. coli can be eliminated in AgCl/Ag3PO4/rGO system within 40 min under visible-light irradiation. Moreover, great stability and reusability were also observed for the ternary photocatalyst. Trapping experiments further confirm that h+ is the most important active specie, which indicates the importance of rGO due to its high electron transfer ability. And the possible photocatalytic mechanisms of AgCl/Ag3PO4/rGO in visible light system were finally proposed.

Application of Fenton, photo-Fenton and electro-Fenton processes for the methylparaben degradation: A comparative study

Endocrine disruptors are often reported in the literature as recalcitrant pollutants in aquatic ecosystems. For this reason, the present study focused on advanced oxidation processes, including Fenton, photo-Fenton, electro-Fenton (EF), and electrochemical oxidation (EO) as an alternative to the degradation of Methylparaben (MeP) from aqueous media. The degradation of MeP by Fenton based processes was completed in 20 min under optimal conditions (16 mg L−1 Fe2+ and 62 mg L−1 H2O2), while for the Photo-Fenton process by a reactor with a 4 W UV lamp, 4 mg L−1 Fe2+ and 52 mg L−1 H2O2, the complete degradation was attained within 16 min. Interestingly, outstanding results were achieved in the Electro-Fenton process carried out in a reactor equipped with a Ti/Ru0,3Ti0,7O2 as a cathode and a platinum anode, which, under optimized conditions (i.e. 4 mg L−1 Fe2+, j = 25 mA cm−2 and 0.05 mol L−1 Na2SO4) only 10 min was required to completely remove the contaminant from both synthetic and tap water. The MeP removal followed pseudo-first-order reaction kinetics in the following order: Electrochemical oxidation (EO) < Fenton < photo-Fenton < electro-Fenton (EF). Finally, after a comparison with the available literature concerning the oxidation of MeP, the EF system here proposed is presented as among the best in removal rate and mineralization as compared with other AOPs, performing better even in real water matrices.

Pd@PdS core shell nanocubes for photocatalytic degradation of methylparaben

We synthesized Pd@PdS core shell nanocubes (NCs) and examined their structural, optical, and electrochemical properties using various analytical techniques. We also demonstrated them as visible light photocatalysts for degrading methylparaben (MEP). The Pd@PdS core shell photocatalyst achieved almost complete removal (∼100%) in 120 min, whereas Pd nanocubes showed a lower degradation efficiency (∼80%). This is attributed mainly to enhanced light absorption and charge transfer at the core shell interface.

Electrochemical degradation of a methyl paraben and propylene glycol mixture: Interference effect of competitive oxidation and pH stability

Endocrine disrupting compounds (EDCs) are one of the many classes of harmful pollutants frequently found in water resources. Even at low concentrations, EDCs might accumulate in the organisms and interfere on numerous processes controlled by hormones. Parabens, for example, are preservatives widely used in pharmaceutical and cosmetic industries, but several studies related them to human breast cancer. It is well-known that electrochemical technologies are an efficient alternative for wastewater treatment, promoting the appropriate destruction of EDCs. However, most studies are applied to single target contaminant solutions, which may neglect the impact from co-exited inorganic/organic pollutants. Based on that, this study aimed to elucidate the interfering effects of two target organic contaminants of very different nature during electrochemical mediated process. For that, methyl paraben (MeP) and propylene glycol (PG) were selected as models of aromatic/phenolic and carboxylate compounds versus low-molecular aliphatic alcohols. These two compounds are often together used in preservative blends and cosmetic/pharmaceutical formulations. PG is not a harmful chemical, but it is present in several types of effluents in relatively high concentrations. Thus, it may interfere on the degradation of numerous pollutants of low concentrations. The electrochemical treatment of a mixture containing 100 mg L−1 MeP +1000 mg L−1 PG showed that both contaminants suffered interfering effects. The presence of MeP negatively interfered on PG degradation; the carboxylate compound is more easily oxidized even at lower molecular concentration. On the other hand, the presence of PG showed an unexpected positive effect on MeP degradation, that was not reflected on its mineralization. The results indicate that in addition to the expected effect of anodic competition, polymerization and copolymerization reactions may also occur in the studied system. The use of an acidic buffer medium increased the removal of both contaminants and favored the oxidation pathway over the polymerization. In this case, the increase in the removal was reflected in the mineralization process, which increased up to 6 times when the mixture was treated in the buffered medium.

Influence of low and high dosages of methyl and propyl parabens on membrane bioreactor (MBR) performance

ABSTRACT This study aimed to evaluate the degradation of methylparaben (MeP) and propylparaben (PrP) in synthetic wastewater in a membrane bioreactor (MBR) whose operation involved three stages: stage 1 (stabilization period), with no addition of parabens; stage 2, in which the MBR was fed with 0.5 mg L−1 of each paraben; and stage 3, in which both MeP and PrP were added, at 10 mg L−1each. The system performance was assessed by monitoring pH, temperature, effluent flow rate, transmembrane pressure, BOD, COD, suspended solids, and paraben concentration. The results confirmed that the MBR showed a good organic matter removal efficiency (> 92.2% for BOD; >91.6% for COD) and was not significantly affected by the addition of parabens at either low or high dosages. The volatile to total suspended solids ratio remained nearly constant, suggesting that the addition of parabens at a high concentration did not negatively impact the control of suspended solids. It was possible to achieve 96.0% of MeP and PrP removal in stage 2 ([parabens]0 = 0.5 mg L−1), and 86.0% of PrP removal in stage 3 ([PrP]0 = 10 mg L−1). Finally, biodegradation was found to be the main removal mechanism of parabens in the investigated MBR.

Methylparaben chlorination in the presence of bromide ions and ammonia: kinetic study and modeling.

The impacts of chlorination on methylparaben (MP) removal, as well as of bromide and ammonia on the MP elimination kinetics, were studied. Bromide and ammonia react with chlorine and are promptly transformed into bromine and chloramines, respectively. Rate constants of chlorine, bromine, and monochloramine with MP were determined under different pH conditions. At pH 8.5, the apparent second-order rate constants of MP reactions with chlorine and bromine were found to be 3.37(±0.50) × 101 and 2.37 (±0.11) × 106 M-1.s-1 for kChlorine/MP and kBromine/MP, respectively, yet there was low reactivity with monochloramine ([Formula: see text] = 0.045 M-1.s-1). Regarding chlorination and bromination, in order to gain further insight into the observed pH-dependence of the reaction, the elementary reactions were considered and the corresponding second-order rate constants were calculated. The experimental and modeled values were quite consistent under these conditions. Then, chlorination experiments with different bromide and/or ammonia concentrations were performed to assess the impact of inorganic water content on MP elimination and a kinetic model was designed to assess MP degradation. Under these conditions, MP degradation was found to be enhanced in the presence of bromide whereas it was inhibited in the presence of ammonia, and the overall impact was pH dependent.

Degradation of aqueous methylparaben by non-thermal plasma combined with ZnFe2O4-rGO nanocomposites: Performance, multi-catalytic mechanism, influencing factors and degradation pathways

Non-thermal plasma (NTP) combined with zinc ferrite-reduced graphene oxide (ZnFe2O4-rGO) nanocomposites were used for the degradation of aqueous methylparaben (MeP). ZnFe2O4-rGO nanocomposites were prepared using the hydrothermal method, with the structure and photoelectric properties of nanocomposites then characterized. The effects of discharge power, initial MeP concentration, initial pH, and air flow rate on MeP degradation efficiency were investigated, and the multi-catalytic mechanism and MeP degradation pathways were established. Results showed that ZnFe2O4-rGO nanocomposites with a 10%:90% mass ratio of GO:ZnFe2O4 had an optimal catalytic effect. The MeP degradation efficiency of NTP combined with ZnFe2O4-rGO (10 wt%), was approximately 25% higher than that of NTP alone. Conditions favorable for MeP degradation included higher discharge power, lower MeP concentration, neutral pH value, and higher air flow rate. The degradation of MeP by NTP combined with ZnFe2O4-rGO nanocomposites followed pseudo-first-order kinetics. O2•-, •OH, H2O2, and O3 were found to play important roles in the MeP degradation, as part of the multi-catalytic mechanism of NTP combined with ZnFe2O4-rGO nanocomposites. MeP degradation pathways were proposed based on the degradation intermediates detected by gas chromatography mass spectrometry, including demethylation, hydroxylation, carboxylation, ring-opening, and mineralization reactions. The prepared ZnFe2O4-rGO nanocomposites provide an approach for improved contaminant degradation efficiency, with reduced energy consumption in the NTP process.

Enhanced removal of methylparaben mediated by cobalt/carbon nanotubes (Co/CNTs) activated peroxymonosulfate in chloride-containing water: Reaction kinetics, mechanisms and pathways

Chloride ion (Cl−) widely presents in natural water and wastewater, which can significantly affect the performance of sulfate radical-based advanced oxidation processes (SR-AOPs). However, few studies are available now on the generation of chlorinated by-products in the peroxymonosulfate (PMS) based systems. Here a novel catalyst (cobalt/carbon nanotubes, Co/CNTs) was synthesized and used as a PMS activator to remove methylparaben (MeP) with and without Cl−. The morphology and chemical composition of the fresh and used Co/CNTs were characterized by TEM, SEM, XRD, BET, and XPS. Results revealed that Co/CNTs exhibited significant catalytic activity toward MeP removal, and the removal efficiency increased with the augment of reaction temperature and concentrations of Co/CNTs and PMS. In the absence of Cl−, 83.2% of 10 μM MeP was degraded within 60 min by using 2 mg/L Co/CNTs and 100 μM PMS at 25 °C with pH 7.0. However, complete removal of MeP was achieved within 20 min in the presence of 100 mM Cl−, which enhanced the apparent rate constant by a factor of 4.3. Consequently, TOC removal was enhanced from 8.1% to 19.2% within 60 min. Through the quenching experiments, both SO4− and OH were found responsible for MeP degradation without Cl−, while Cl2− was the main reactive oxygen species (ROS) with 100 mM Cl−. Based on the intermediates identified via TOF-LC-MS, four potential reaction pathways were proposed, including hydrogen abstraction coupling reaction, hydroxylation, OH attack, and Cl2− attack. The intermediates also exhibited decreased toxicity compared to the parent compound based on the ecotoxicity evaluation. In addition, Co/CNTs + PMS system achieved over 60% MeP removal from real wastewater with elevated PMS concentration, indicating the process applicability. These findings provide valuable information of SR-AOPs to facilitate organic contaminants removal in Cl−-containing water.

Enhanced visible light-driven photocatalytic activity of reduced graphene oxide/cadmium sulfide composite: Methylparaben degradation mechanism and toxicity

Reduced graphene oxide/cadmium sulfide (RGOCdS) nanocomposite synthesized through solvothermal process was used for methylparaben (MeP) degradation. The crystallinity of the nanocomposite was ascertained through X-ray diffraction. High resolution transmission electron microscope (HRTEM) results proved the absence of any free particle beyond the catalyst surface ensuring the composite nature of the prepared material. The enhancement in the activity on doping with RGO was substantiated by diffuse reflectance spectroscopy (DRS-UV). It is evident from the photocatalytic degradation experiments that RGOCdS is more efficient than pure CdS. Maximum MeP degradation (100%) was achieved after 90 min of irradiation with 750 mg/L RGOCdS dosage at an acidic pH of 3, for an initial MeP concentration of 30 mg/L. The degradation mechanism substantiated through HPLC-MS/MS analysis showed the complete degradation of MeP without any residual intermediaries. The catalyst could be sustained and reused for up to 9 cycles of usage. Phytotoxicity and mycotoxicity results evidently ascertain the environmental implications of the photocatalyst material.

Solar light‐induced photocatalytic degradation of methylparaben by g‐C3N4 in different water matrices

AbstractBACKGROUNDIn this study, graphitic carbon nitride (g‐C3N4) photocatalyst was successfully synthesized via calcination of urea under argon flow and tested for methyl paraben (MeP) degradation in aqueous media under simulated solar light for the first time. Its structural, morphological, and optical properties were investigated with the use of X‐Ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and Brunauer‐Emmett‐Teller (BET) surface area analysis method.RESULTSThe as‐synthesized g‐C3N4 exhibited high photocatalytic performance towards the degradation of MeP in ultra‐pure water (UPW), yielding a near‐complete elimination after 90 min of irradiation. Experimental results revealed that the photocatalytic reaction followed pseudo‐first‐order kinetics. Furthermore, the photocatalytic degradation of MeP was found to be strongly pH‐dependent. Experiments in real water matrices (bottled water (BW) and wastewater (WW)), as well as in UPW, spiked with inorganic and organic additives (bicarbonate ions, humic acid) affected the target compound degradation. For instance, the apparent rate constant of MeP in UPW was approximately 4 and 8 times greater than that of BW and WW, respectively. The addition of persulfate ions in the reaction mixture enhanced the performance of the present photocatalytic system. Trapping experiments revealed that photogenerated holes play a leading role in the photocatalytic degradation of MeP.CONCLUSIONOur findings demonstrate that g‐C3N4 photocatalysis can be used as an efficient technology for the removal of hazardous organic micropollutants, such as parabens. © 2020 Society of Chemical Industry (SCI)

Degradation of methylparaben by sonocatalysis using a Co-Fe magnetic carbon xerogel.

The degradation of methylparaben (MP) through 20kHz ultrasound coupled with a bimetallic Co-Fe carbon xerogel (CX/CoFe) was investigated in this work. Experiments were performed at actual power densities of 25 and 52W/L, catalyst loadings of 12.5 and 25mg/L, MP concentrations between 1 and 4.2mg/L and initial pH values between 3 and 10 in ultrapure water (UPW). Matrix effects were studied in bottled water (BW) and secondary treated wastewater (WW), as well as in UPW spiked with bicarbonate, chloride or humic acid. The pseudo-first order kinetics of MP degradation increase with power and catalyst loading and decrease with MP concentration and matrix complexity; moreover, the reaction is also favored at near-neutral conditions and in the presence of dissolved oxygen. The contribution of the catalyst is synergistic to the sonochemical degradation of MP and the extent of synergy is quantified to be >45%. This effect was ascribed to the ability of CX/CoFe to catalyze the dissociation of hydrogen peroxide, formed through water sonolysis, to hydroxyl radicals. Experiments in UPW spiked with an excess of tert-butanol (radical scavenger), sodium dodecyl sulfate or sodium acetate (surfactants) led to substantially decreased rates (i.e. by about 8 times), thus implying that the liquid bulk and the gas-liquid interface are major reaction sites. The stability of CX/CoFe was shown by performing reusability cycles employing magnetic separation of the catalyst after the treatment stage. It was found that the CX/CoFe catalyst can be reused in up to four successive cycles without noteworthy variation of the overall performance of the sonocatalytic process.

Synergistic degradation of methylparaben on CuFe2O4-rGO composite by persulfate activation

Methylparaben (MeP), as emerging contaminants widely used in pharmaceuticals and personal care products, have potential endocrine disrupting effect. In this study, the copper ferrite (CuFe2O4) nanoparticles were uniformly distributed on graphene oxide (GO), and the performance and mechanism of CuFe2O4-rGO composites in activating persulfate (PS) for MeP degradation were comprehensively investigated. Results showed that the CuFe2O4-rGO composites exhibited much better efficiency for MeP degradation than CuFe2O4, and the synergistic effect between CuFe2O4 and GO in CuFe2O4-rGO composite was also observed. The best catalytic performance of CuFe2O4-rGO composites was obtained at the mass ratio of 4:1 for CuFe2O4 to GO and at neutral pH. X-ray photoelectron spectroscopy (XPS) results suggested that graphene in the composites mainly served as an electron shuttle to mediate electron transfer reactions. Electron paramagnetic resonance (EPR) and the quenching experiments further revealed that both hydroxyl and sulfate radicals were the major reactive species, and non-radical process also occurred during the reaction. Meanwhile, the degradation pathways of MeP involving hydroxylation, decarbonylation and ring opening were rationally proposed based on computational method and intermediates identification. All these results could provide insight into persulfate activation by CuFe2O4-rGO nanocomposites in environmental control applications.

Method for Visible Light-Induced Photocatalytic Degradation of Methylparaben in Water Using Nanostructured Ag/AgBr@m-WO3.

An efficient method of photocatalytic degradation of methylparaben in water using Ag nanoparticles (NPs) loaded AgBr-mesoporous-WO3 composite photocatalyst (Ag/AgBr@m-WO3 ), under visible light is presented. In this process, quantification of methylparaben in water was carried out by high-performance liquid chromatography (HPLC) and the HPLC results showed a significant reduction of methylparaben in water due to the enhanced of photocatalytic degradation efficiency of Ag/AgBr@m-WO3 . For the material synthesis, highly ordered mesoporous-WO3 (m-WO3 ) was initially synthesized by sol-gel method and AgBr nanoparticles (NPs) were subsequently introduced in the pores of m-WO3 , and finally, the Ag nanoparticles were introduced by light irradiation. The enhanced photocatalytic degradation of methylparaben in water is attributed to the formation of surface plasmonic resonance (SPR) due to the introduction of Ag NPs on the surface of the catalyst. Also, the formation of heterojunction between AgBr and mesoporous-WO3 in Ag/AgBr@m-WO3 significantly inhibited the recombination of light-induced electron-hole pairs in the semiconductor composite. The morphological and optical characterizations of the synthesized photocatalysts (Ag/AgBr@m-WO3 ) were carried out using SEM, TEM, XDR, N2 adsorption-desorption, UV-VIS diffuse reflectance spectroscopy (DRS). Also, the photocatalytic studies using radical scavengers were carried out and the results indicated that is the main reactive species.

Optimization of methylparaben degradation by sonocatalysis.

Sonocatalytic degradation of methylparaben (MPB) in the presence of a low-cost clay mineral (sepiolite) was optimized using a multivariable center composite design protocol based on response surface methodology (RSM). Using the data generated with varying MPB concentrations, pH, frequency and catalyst dose, two semi-empirical expressions were developed to describe the relation between the apparent reaction rate constant of the parent compound and the most significant control variables. It was found that ultrasonic power, pH, sepiolite dose and its interactions with time and pH were the most significant parameters influencing the rate of MPB decay under high frequency ultrasound. The models also showed that the rate constant was a convex function of time, as it decreased during the first 35-min of sonolysis and increased thereafter, indicating the formation and depletion of competing oxidation byproducts. Finally, the models predicted that the rate of MPB decay was a maximum either at alkaline pH and a high sepiolite dose (k = 1.68 × 10-1 min-1), or at acidic pH and a considerably lower dose of the mineral (k = 1.48 × 10-1 min-1).

Nitrogen-sulfur co-doped industrial graphene as an efficient peroxymonosulfate activator: Singlet oxygen-dominated catalytic degradation of organic contaminants

This paper presents for the first time the doping of nitrogen (N) and sulfur (S) into industrial reduced graphene oxide (i-rGO) to synthesize the catalyst, named as i-rGO-NS, to activate peroxymonosulfate (PMS). Co-doping of N and S into the catalyst was investigated by many surface techniques. The i-rGO-NS catalyst had the higher content of graphitic N (˜34%) than only N-doped rGO (i.e., i-rGO-N). The i-rGO-NS showed high activation of PMS for catalyzing oxidation of target contaminant, methyl paraben (MP), an endocrine disruptor in water under various conditions (reaction temperature, catalyst loading and PMS dosage). In comparison with the conventional GO and its N-doped or N/S-co-doped composites and classical metal catalysts (e.g., Co3O4 and Fe3O4), i-rGO-NS has superior effectiveness to activate PMS to degrade contaminants even under the conditions of less dosage of the catalyst (i-rGO-NS) and oxidant (PMS). Results suggest that the N doping, and especially additional S doping were of pivotal in enhancing catalytic performance. Transformation pathways of MP in the i-rGO-NS/PMS system were tentatively proposed that agree with the identified intermediates and frontier electron density calculations. Quenching tests and electron paramagnetic resonance (EPR) studies showed that the singlet oxygen (1O2) was the main reactive oxygen species, revealing that MP degradation follows predominantly the nonradical oxidation pathway. The i-rGO-NS/PMS system not only exhibited considerable removal efficiency of MP in real waters, but also showed the rapid degradation of other pollutants (e.g., UV filter benzophenone-4 (BP-4) and phenol) in water. The newly developed nonradical i-rGO-NS/PMS process is highly effective in decontamination of water.

Heterogeneous catalytic degradation of methylparaben using persulfate activated by natural magnetite; optimization and modeling by response surface methodology

AbstractBACKGROUNDIn this study, a naturally magnetic semiconductor mineral (NM‐SCM) was used as a highly active, easily separable and green catalyst to activate persulfate (SPS) for the degradation of methylparaben (MeP) in aqueous solution by a heterogeneous catalyst system (SPS/NM‐SCM). NM‐SCM properties were characterized using field emission scanning electron microscope (FESEM), Brunauer–Emmett–Teller (BET), X‐ray diffraction (XRD), energy‐dispersive X‐ray (EDX) and vibrating sample magnetometer (VSM) analyses. The effects of contributing factors such as solution pH, NM‐SCM loading, SPS dosage and initial MeP concentration on MeP degradation were analyzed using response surface methodology (RSM) and Box–Behnken design (BBD).RESULTSThe RSM model obtained from the present study (R2 &gt; 0.99) showed a suitable correlation between the predicted values and experimental results of MeP degradation. Under optimized conditions (pH 6.5, SPS 5 mmol L−1, NM‐SCM 0.3 g L−1 and MeP 10 µmol L−1), a removal efficiency of 99.5% and a mineralization degree of 37% were achieved. The removal efficiency of MeP was reduced in the presence of inorganic ions as follows: chloride &gt; nitrate &gt; carbonate &gt; phosphate. After five successive catalyst reuses, the degradation efficiency was &gt;90%, indicating the excellent potential reusability of NM‐SCM catalyst.CONCLUSIONOwing to the generation of highly reactive oxidizing species (SO4•−) and easy separation of the catalyst, the integration of NM‐SCM and SPS has great potential for the degradation of MeP from water and wastewater matrices. © 2019 Society of Chemical Industry

Degradation of methylparaben using BiOI-hydrogel composites activated peroxymonosulfate under visible light irradiation

A novel hydrogel photocatalyst (p(HEA-APTM)-BiOI) was synthesized by irradiation polymerization and chemical precipitation method, while employed as peroxymonosulfate (PMS) activator to enhance methylparaben (MP) degradation. The structure, morphology and physicochemical properties of the prepared p(HEA-APTM)-BiOI were characterized by XRD, XPS, SEM, TEM, FTIR and BET. The experimental results revealed that the MP catalytic degradation by p(HEA-APTM)-BiOI activated PMS can achieve the best performance under the visible light irradiation. In addition, the parameters including the molar radio of [PMS]/[MP], initial pH, Cl− and HCO3− were also investigated in detail. It was worth noting that p(HEA-APTM)-BiOI also effectively eliminated MP in the absence of visible light. Based on the quenching experiment, 1O2, h+ and O2− were determined as the dominant active species contributing to the catalytic oxidation process in the p(HEA-APTM)-BiOI/PMS/Vis system, and the possible degradation mechanism was also elaborated. Eventually, the possible pathways of MP degradation were deduced from several intermediates identified by HPLC-MS.

Synthesis and Application of Fe-Doped WO3 Nanoparticles for Photocatalytic Degradation of Methylparaben Using Visible–Light Radiation and H2O2

Synthesis of WO3 and Fe-doped WO3 nanoparticles is done by use of Microwave irradiation technique. X-ray powder diffraction confirmed the formation of a monoclinic crystalline structure. The as-prepared samples are characterised by transmission electron microscope, Braunuer, Emmett and Teller, Raman spectroscopy, photoluminescence, X-ray photoelectron spectroscopy and ultraviolet diffuse reflectance spectroscopy. Confirmation of the morphology of the nanostructures showed ovoid-like form. The photocatalytic activity of WO3 and nominal percentage of Fe-doped WO3 (3, 5 and 10 wt%) are evaluated for the degradation of methylparaben (MeP) in aqueous solution after being irradiated with visible light. The results show that 5 wt% Fe–WO3 is the best dopant in the photodegradation of MeP at 50.8% with H2O2. A chemometric model analysis is applied to estimate both individual and interaction factors that included pH, contact time, hydrogen peroxide (H2O2) concentration and catalyst dosage. The optimal conditions at pH 3, 10 mg, 5 wt% Fe–WO3 and 120 min are achieved.

Aqueous methylparaben degradation by dielectric barrier discharge induced non-thermal plasma combined with ZnO-rGO nanosheets

The feasibility of methylparaben (MeP) degradation in aqueous solution by dielectric barrier discharge induced non-thermal plasma combined with zinc oxide-reduced graphene oxide (ZnO-rGO) nanosheets was investigated. The ZnO-rGO nanosheets were synthesized by hydrothermal method and characterized by X-ray diffraction, nitrogen adsorption-desorption isotherm, scanning electron microscope, transmission electron microscope, UV–vis absorption spectroscopy, photocurrent, photoluminescence spectroscopy and X-ray photoelectron spectroscopy. The effects of various factors (discharge power, initial concentration of MeP, initial pH value and air flow rate) on the degradation of MeP were evaluated and the changes of solution pH, conductivity and TOC during the degradation process were discussed. The results showed that when the discharge power was 20 W, the airflow rate was 20 L/h, the ZnO-rGO nanosheets dosage was 0.015 g/L, the initial concentration of MeP was 20 mg/L, and the initial pH value was 7.0, the degradation efficiency of MeP achieved 99% at 15 min. The adding of ZnO-rGO nanosheets to the non-thermal plasma system greatly enhanced the degradation efficiency of MeP. In addition, the role of some reactive species during the degradation process of MeP was also investigated. The degradation process of MeP was well fitted by the pseudo-first-order kinetics. Good stability of the synthetic ZnO-rGO was observed. The degradation intermediates of MeP were determined by gas chromatography-mass spectrometer and the degradation pathways were proposed. Under the attack of reactive species, conjugated structure destruction, hydroxylation, carboxylation and ring-opening reaction occurred during MeP degradation, resulting in the formation of organic acids and alcohols; furthermore, some of the degradation intermediates were mineralized to H2O and CO2.