Degradation Of Ethyl Paraben Research Articles

Fighting poison with poison: Degradation of ethyl paraben by Bi2Ti2O7-TiO2 doped with ethyl paraben

In this paper, a variety of titanium-bismuth-based composite photocatalysts were prepared by molecularly imprinted sol–gel method using ethyl paraben (EP) as the target pollutant and tetra-n-butyl titanate as the precursor for the degradation of EP. The photocatalytic removal of 81.4 % of 10 mg/L EP wastewater was achieved by synthesising Bi-EP-TiO2 for 30 min at 500°C, 5 g Bi and 2 g EP. The main component of the prepared Bi-EP-TiO2 and Bi-TiO2 is Bi2Ti2O7-TiO2. In addition, the forbidden bandwidth of Bi-EP-TiO2 is 0.28 eV larger than that of Bi-TiO2 but 0.30 eV smaller than that of TiO2, which suggests that, compared with TiO2, Bi-EP-TiO2 requires a lower electron-leap energy, which is capable of generating more. This suggests that Bi-EP-TiO2 requires lower electron transition energy than TiO2, and therefore can generate more photogenerated electron holes, thus improving the catalytic efficiency. Hence, Bi2Ti2O7-TiO2 doped with ethyl paraben degrades EP with excellent performance.

Hydrothermal Synthesis of rGO-TiO2 Composites as High-Performance UV Photocatalysts for Ethylparaben Degradation

A series of reduced graphene oxide-TiO2 composites (rGO-TiO2) were prepared by hydrothermal treatment using graphite and titanium isopropoxide as raw materials. The structural, surface, electronic, and optical properties of the prepared composites were extensively characterized by N2 adsorption, FTIR, XRD, XPS, Raman spectroscopy, and DRS. GO was found to be effectively reduced and TiO2 to be in pure anatase phase in all composites obtained. Finally, experiments were performed to evaluate the effectiveness of these new materials as photocatalysts in the degradation of ethylparaben (EtP) by UV radiation. According to the band-gap energies obtained (ranging between 3.09 eV for 4% rGO-TiO2 to 2.55 eV for 30% rGO-TiO2), the rGO-TiO2 composites behave as semiconductor materials. The photocatalytic activity is highest with a rGO content of 7 wt% (7% rGO-TiO2), being higher than observed for pure TiO2 (Eg = 3.20 eV) and achieving 98.6% EtP degradation after only 40 min of treatment. However, the degradation yield decreases with higher percentages of rGO. Comparison with rGO-P25 composites showed that a better photocatalytic performance in EtP degradation is obtained with synthesized TiO2 (rGO-TiO2), probably due to the presence of the rutile phase (14.1 wt %) in commercial P25.

Photocatalytic Evaluation of Ag2CO3 for Ethylparaben Degradation in Different Water Matrices

The present study examines the photocatalytic properties of silver carbonate (Ag2CO3) for ethyl paraben (EP) degradation under simulated solar irradiation. Ag2CO3 was prepared according to a solution method and its physicochemical characteristics were studied by means of X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). Complete EP (0.5 mg/L) removal was achieved after 120 min of irradiation with the use of 750 mg/L Ag2CO3 in ultrapure water (UPW), with EP degradation following pseudo-first-order kinetics. The effect of several experimental parameters was investigated; increasing catalyst concentration from 250 mg/L to 1000 mg/L led to an increase in EP removal, while increasing EP concentration from 0.25 mg/L to 1.00 mg/L slightly lowered kapp from 0.115 min−1 to 0.085 min−1. Experiments carried out with the use of UV or visible cut-off filters showed sufficient EP degradation under visible irradiation. A series of experiments were performed in real water matrices such as bottled water (BW) and wastewater (WW), manifesting Ag2CO3’s equally high photocatalytic activity for EP degradation. To interpret these results different concentrations of inorganic anions (bicarbonate 100–500 mg/L, chloride 100–500 mg/L) present in aqueous media, as well as 10 mg/L organic matter in the form of humic acid (HA), were added sequentially in UPW. Results showed accelerating effects on EP degradation for the lowest concentrations tested in all cases.

Degradation of ethyl paraben in aqueous medium using advanced oxidation processes: Efficiency evaluation of UV-C supported oxidants

Abstract UV-C-mediated advanced oxidation processes (AOPs) for the enhanced degradation of ethyl paraben (EP) in the presence of oxidants such as persulfate (PS), hydrogen peroxide (H2O2) and peroxymonosulfate (PMS) were systematically investigated. The AOP treatments showed 98.1%, 97.0% and 81.3% degradation of EP with rates of 0.0373, 0.0339, and 0.0202 min−1 within 90 min for UV/PS, UV/H2O2 and UV/PMS, respectively. Degradation rates of EP increased with higher initial dosages of oxidant(s), while the opposite trend was observed in the case of increasing initial EP concentration. Maximum EP removal was achieved at pH 6.5 for UV/PS and UV/PMS and at pH 3 for UV/H2O2. Humic acid significantly retarded the degradation of EP. Chloride (Cl−) and carbonate (CO32−) suppressed reaction rates using UV/PS and UV/H2O2 systems, whereas they elevated the degradation rates with UV/PMS treatment. Degradation of EP in each of the UV-C based AOPs followed pseudo-first-order kinetics. The use of ethanol and t-butyl alcohol as scavengers revealed that HO and radicals were the major reactive radicals in UV/H2O2, UV/PS, and UV/PMS treatments. The efficiency (according to electrical energy per order and total cost per cubic meter) of the systems followed the order UV/PS > UV/H2O2 > UV/PMS. Thus, UV/PS process was more efficient and economical for EP degradation than the other processes examined in this study.

Degradation of ethylparaben using photo-Fenton-like oxidation over BiFeO3

The degradation of ethylparaben using photo-Fenton-like oxidation was investigated in the presence of a BiFeO 3 catalyst. Firstly, the catalyst was synthesized using the sol-gel method and then, a parametric study was carried out in order to determine the optimum reaction conditions for the degradation of ethylparaben. In this context, the effects of catalyst loading, [H 2 O 2 ] o , pH, and temperature on the degradation were investigated. According to the results, the optimum reaction conditions were determined for a 5 ppm ethylparaben solution as 0.25 g/L catalyst loading, a pH of 3, and 2 mM [H 2 O 2 ] o and a 97.7% degradation of ethylparaben was accomplished. Iron leaching at the optimum conditions was evaluated as 1.53 ppm and it is lower than the E.U. iron concentration limitation (2 ppm) in the water. The kinetic study was carried out at the optimum reaction conditions at three different temperatures (25, 35, and 45 °C). The degradation of ethylparaben using photo-Fenton-like oxidation fitted the first order reaction kinetic model. The reaction rate constants were determined as 0.041, 0.050, and 0.069 min -1 for 25, 35, and 45 °C, respectively. The activation energy was found as 20.4 kJ/mol.

Boron-doped diamond electrooxidation of ethyl paraben: The effect of electrolyte on by-products distribution and mechanisms

Ethyl paraben (EP), a representative emerging pollutant of the parabens family, was subject to electrochemical oxidation over a boron-doped diamond (BDD) anode. Experiments were carried out in a single-compartment cell at 10–70 mA cm−2 current density, 200–600 μg L−1 EP concentration, initial solution pH 3–9 and 0.1 M electrolyte concentration. The degradation rate is favored at increased current densities and in the presence of NaCl as the supporting electrolyte, while the pH effect is inconsiderable. For instance, the first order rate constant for the degradation of 200 μg L−1 EP at 30 mA cm−2 was 0.25, 0.1 and 0.07 min−1 with NaCl, Na2SO4 and HClO4, respectively. Degradation in secondary treated wastewater was faster than in pure water presumably due to the action of chloride ions present in the effluent.Liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) was employed to determine major transformation by-products (TBPs). The route of EP degradation with Na2SO4 involves hydroxylation and demethylation reactions, signifying the role of electrogenerated hydroxyl radicals in the process. Twenty one TBPs were identified with NaCl as the electrolyte, including several chlorinated and non-chlorinated dimers and trimers; these findings suggest that indirect oxidation mediated by chlorine radicals and other chlorine active species also takes place. In this view, the role of the supporting electrolyte is crucial since it can influence both reaction kinetics and pathways.

Solar photocatalytic decomposition of ethyl paraben in zinc oxide suspensions

The photocatalytic degradation of ethyl paraben (EP) in zinc oxide (ZnO) suspensions under simulated solar radiation was investigated. The effect of EP concentration (500–1500μg/L), ZnO concentration (100–500mg/L), reaction time (3–9min), initial pH (3–9), light intensity (7.3 10−7–1.1 10−6 einstein/(L.s)) and the water matrix (0–10mg/L of humic acid) on degradation was evaluated implementing a factorial design methodology. Of the six variables tested, EP concentration, ZnO concentration, reaction time and the water matrix were found to be statistically significant variables, and also important was the second order interaction of EP concentration with reaction time. With the exception of the water matrix, all other effects were positive with respect to the concentration of EP removed.Experiments at increased EP concentration (20mg/L) were performed to identify transformation products (TPs) and assess the extent of mineralization. LC-TOF-MS analysis revealed the formation of seven early-stage TPs through hydroxylation and dealkylation reactions and a plausible reaction pathway was proposed. Besides the identified TPs, other unidentified TPs were also formed as has been verified measuring the extent of mineralization and performing a carbon balance in the liquid phase. EP at 20mg/L exhibited mild estrogenic activity, which was partially removed upon oxidation. The stability of ZnO was evaluated measuring the extent of zinc leaching, which was just 1.5%; moreover, ZnO was found to be more active than reference P25 TiO2 for EP degradation and mineralization.

Solar light-induced degradation of ethyl paraben with CuOx/BiVO4: Statistical evaluation of operating factors and transformation by-products

In this work, the solar light-induced photocatalytic degradation of ethyl paraben (EP) was studied using CuOx/BiVO4 with 0.75wt.% copper loading, a relatively new photocatalyst that can exploit a large portion of the solar spectrum. The synthesized catalyst had a primary crystallite size of ca 37nm, a specific surface area of 1m2/g and a direct bandgap of 2.3eV. A factorial design methodology was implemented to evaluate the importance of EP concentration (500–1500μg/L), catalyst concentration (100–500mg/L), reaction time (10–60min), the presence of radical scavengers (pure water or 500mg/L bicarbonates) and initial solution pH (3–9) on EP removal. All individual effects were statistically significant and so was the second-order interaction of EP concentration with reaction time. Interestingly and differently from the majority of photocatalytic studies, the presence of bicarbonates promotes the photocatalytic degradation of ethyl paraben. The photocatalytic activity drops from 98% to 79% after five consecutive runs, possibly due to accumulation of oxidation by-products. Liquid chromatography-time of flight mass spectrometry (LC-TOF-MS) revealed that EP degradation occurs mainly via dealkylation followed by hydroxylation reactions and the formation of methyl paraben, 4-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid and 3,4-dihydroxybenzoic acid as primary transformation by-products.

Degradation of ethyl paraben by heat-activated persulfate oxidation: statistical evaluation of operating factors and transformation pathways.

A factorial design methodology was implemented to evaluate the importance of ethyl paraben (EP) concentration (500-1500μg/L), sodium persulfate concentration (400-500mg/L), temperature (40-60°C), reaction time (2-30min), water matrix (pure water or secondary treated wastewater), and initial solution pH (3-9) on EP removal by heat-activated persulfate oxidation. All individual effects, except the solution pH, were statistically significant and so were the second-order interactions of ethyl paraben concentration with temperature or the reaction time. The influence of the water matrix was crucial, and the efficiency of the process was lower in secondary treated wastewater due to the presence of natural organic matter and inorganic salts that compete with ethyl paraben for the reactive oxygen species. Liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) was employed to identify major transformation by-products (TBPs); 13 compounds were detected as TBPs of EP. Degradation occurred through (i) hydroxylation, (ii) dealkylation, and (iii) oligomerization reactions leading to TBPs with ether and biphenyl structures. Oligomerization reactions were found to be the dominant pathway during the first steps of the reaction. The toxicity of 500μg/L EP in secondary treated wastewater was tested against marine bacteria Vibrio fischeri; toxicity increased during the first minutes due to the production of several TBPs, but it consistently decreased thereafter.

On the capacity of ozonation to remove antimicrobial compounds, resistant bacteria and toxicity from urban wastewater effluents

The degradation of erythromycin (ERY) and ethylparaben (EtP) in urban wastewater effluents at low concentration level during ozonation was investigated under different experimental conditions. Both substrates were rapidly eliminated within 2min at low ozone dose of 0.3mgL−1 and the experimental data were well fitted in the pseudo-first-order kinetic model. The ratio of HO- and O3-exposure (Rct) at the inherent pH was found to be 1.9×10−8. The degradation of ERY and EtP was pronounced at pH 8 compared to acidic pH conditions, while the degradation rate of both substrates was found to be matrix-depended. It was also shown that both O3- and HO-mediated pathways are involved in the degradation of EtP, whereas the saturated-rich structure of ERY renders it O3-recalcitrant. Under the optimum O3 dose, the BrO3− concentration was found to be lower than 10μgL−1. Five and fifteen transformation products were elucidated during ERY and EtP oxidation, respectively. The root and shoot inhibition can be attributed to the oxidation products formed upon dissolved effluent organic matter transformation. Escherichia coli harbouring resistance to ERY survived ozonation better than EtP-resistant E. coli. However, neither ERY- nor EtP-resistant E. coli were detected after 15min of ozonation.

Kinetics of ethyl paraben degradation by simulated solar radiation in the presence of N-doped TiO2 catalysts

Ethyl paraben (EP), an emerging micro-pollutant representative of the parabens family, has been subject to photocatalytic degradation under simulated solar radiation at a photon flux of 1.3·10−4 E/(m2 s). Six nitrogen-doped titania catalysts synthesized by annealing a sol–gel derived TiO2 powder under ammonia flow and their un-doped counterparts, calcined in air at different temperatures in the range 450–800 °C, were compared under solar and visible light and the most active one (N-doped TiO2 calcined at 600 °C) was used for further tests.Experiments were performed at EP concentrations between 150 and 900 μg/L, catalyst loadings between 100 and 1000 mg/L, pH between 3 and 9, different matrices (ultrapure water, water spiked with humic acids or bicarbonates, drinking water and secondary treated wastewater) and hydrogen peroxide between 10 and 100 mg/L. For EP concentrations up to 300 μg/L, the degradation rate can be approached by first order kinetics but then shifts to lower order as the concentration increases. The rate increases linearly with catalyst loading up to 750 mg/L and hydrogen peroxide up to 100 mg/L. Near-neutral (pH = 6.5–7.5) and alkaline conditions (pH = 9) do not affect degradation, which is reduced at acidic pH. The presence of humic acids at 10–20 mg/L impedes degradation due to the competition with EP for the oxidizing species and this is more pronounced in actual wastewater matrices.UPLC-ESI-HRMS and HPLC-DAD were employed to follow EP concentration changes, as well as identify and quantify transformation by-products during the early stages of the reaction. Five such products were successfully detected and, based on their concentration–time profiles, a reaction network for the degradation of EP is proposed. Hydroxyl radical reactions appear to prevail during the initial steps as evidenced by the rapid formation of hydroxylated and dealkylated intermediates.