Solar photocatalitycal treatment of carbofuran at lab and pilot scale: effect of classical parameters, evaluation of the toxicity and analysis of organic by-products

Photocatalytic Degradation of Carbofuran in Water Using Laser-Treated TiO2: Parameters Influence Study, Cyto- and Phytotoxicity Assessment

This study investigates the impact of changing parameters on the photocatalytic degradation of carbofuran (CBF) using laser-treated TiO2 nanotube arrays on a Ti mesh under simulated sunlight irradiation and assessing toxicity during photocatalytic degradation. Various parameters, including the stirring effect, light intensity, initial CBF concentration, and variation in the active surface area of laser-treated TiO2 photocatalysts, were examined to determine their impact on degradation efficiency. The photodegradation kinetics were monitored using ultra-performance liquid chromatography with a PDA detector (UPLC-PDA) and UV-Vis spectrophotometry, while mineralization was assessed by a total organic carbon (TOC) analyzer. The photocatalytic degradation of CBF is enhanced by an increase in the active surface area of the TiO2 photocatalyst, light intensity, and the introduction of stirring, but it decreases with an increase in the initial concentration of CBF. The toxicity assessments revealed that the cytotoxicity of CBF initially increased during the degradation process but decreased after further treatment, indicating the formation and subsequent breakdown of toxic intermediates. The phytotoxicity test showed that longer degradation times resulted in higher toxicity to plant growth. This study provides new insights into the photocatalytic degradation of CBF with TiO2, the importance of parameter optimization for more efficient treatment, and the use of toxicity tests to confirm the success of the photocatalytic process.

Photocatalytic degradation of parabens: A comprehensive meta-analysis investigating the environmental remediation potential of emerging pollutant

The increasing prevalence of paraben compounds in the environment has given rise to concerns regarding their detrimental impacts on both ecosystems and human health. Over the past few decades, photocatalytic reactions have drawn significant attention as a method to accelerate the otherwise slow degradation of these pollutants. The current study aims to evaluate the current efficacy of the photocatalytic method for degrading parabens in aqueous solutions. An extensive literature review and bibliometric analysis were conducted to identify key research trends and influential areas in the field of photocatalytic paraben degradation. Studies were screened based on the predetermined inclusion and exclusion criteria, which led to 13 studies that were identified as being appropriate for the meta-analysis using the random effects model. Furthermore, experimental parameters such as pH, paraben initial concentration, catalyst dosage, light intensity, and contact time have been reported to have key impacts on the performance of the photocatalytic degradation process. A comprehensive quantitative assessment of these parameters was carried out in this work. Overall, photocatalytic techniques could eliminate parabens with an average degradation efficiency of >80 %. The findings of the Egger's test and the Begg's test were statistically not significant suggesting potential publication bias was not observed. This review provides a holistic understanding of the photocatalytic degradation of parabens and is anticipated to encourage more widespread adoption of photocatalytic procedures as a suitable method for the elimination of parabens from aqueous solutions, opening new avenues for future research in this direction.

Degradation of carbofuran and acetamiprid in wolfberry by dielectric barrier discharge plasma: Kinetics, pathways, toxicity and molecular dynamics simulation

Carbofuran and acetamiprid pose the highest residual risk among pesticides found in wolfberries. This study aimed to degrade these pesticides in wolfberries using a multi-array dielectric barrier discharge plasma (DBD), evaluate the impact on safety and quality and explore their degradation mechanism. The results showed that DBD treatment achieved 90.6% and 80.9% degradation rates for carbofuran and acetamiprid, respectively, following a first-order kinetic reaction. The 120 s treatment successfully reduced pesticide contamination to levels below maximum residue limits. Treatment up to 180 s did not adversely affect the quality of wolfberries. QTOF/MS identification and degradation pathway analysis revealed that DBD broke down the furan ring and carbamate group of carbofuran, while replacing the chlorine atom and oxidizing the side chain of acetamiprid, leading to degradation. The toxicological evaluation showed that the degradation products were less toxic than undegraded pesticides. Molecular dynamics simulations revealed the reactive oxygen species (ROS) facilitated the degradation of pesticides through dehydrogenation and radical addition reactions. ROS type and dosage significantly affected the breakage of chemical bonds associated with toxicity (C4-O5 and C2-Cl1). These findings deepen insights into the plasma chemical degradation of pesticides.

Multivariate effect of inorganic wastewater matrix on the removal of pesticides by solar photo-Fenton

An amount of works has reported the effect of wastewater matrix composition on pollutants removal by different AOPs. The biggest challenge is that each wastewater source has a challenging composition (organic and inorganic compounds, pollutants, etc.) and not only the concentration of all these species but also the interaction between them may affect the effectiveness of the studied process. This work has been carried out to evaluate the photo-degradation kinetics of six different pesticides (flutriafol, imidacloprid, myclobutanil, pirimicarb, thiamethoxam and triadimenol) by solar photo-Fenton (SPF) process at acidic pH. First, oxidant concentration (H2O2) was optimized with an actual WWTP effluent. Then, the process was validated with two different secondary and tertiary WWTP effluents, in which main intermediate transformation by-products were identified. Finally, the effect of the inorganic water matrix components (bicarbonate, chloride, sulphate, nitrate and phosphate) was evaluated by a multivariate analysis. Once H2O2 has been optimized at 30 mg L-1, the photo-degradation efficiency of pesticides in real wastewater samples was compared. DOC content of both secondary and tertiary WWTP effluents was dropped by 67%. The identification of the main intermediate transformation by-products (such as 1H-1,2,4-triazole, desmethyl-formamido pirimicarb, thiamethoxam urea, chloronicotinic acid and imidacloprid urea) was reviewed. Following, the multivariate analysis on pesticides photo-degradation, generally, predicted four significant effects in common for the studied pesticides: a positive effect (interaction bicarbonate/nitrate) and three negative ones (chloride, phosphate and the interaction chloride/sulphate); among others. In addition, optimum values of inorganic ion concentrations, to obtain an optimum desirability on studied pesticides removal by SPF at acidic pH, were also evaluated.

Cefotaxime removal enhancement via bio-nanophotocatalyst α-Fe2O3 using photocatalytic degradation technique and its echo-biomedical applications

The present paper evaluates the photocatalytic degradation (PCD) performance of the biofabricated hematite nanoparticles (α-HNPs) for the degradation approach of the Cefotaxime (Cfm). The optimum pH of the solution to achieve the best PCD was found to be 10.5. The kinetics study for the PCD of the Cfm via α-HNPs has been investigated and the reaction was found to be fellow pseudo-first-order at R2 = 0.992. The mass loading impact of α-HNPs was investigated and estimated for the maximum degradation of Cfm 0.4 mg/mL. UV-Vis confirmed that α-HNPs had a direct transition bandgap at 3.78 eV at a maximum absorption wavelength of 362 nm with suspension stability for 7 days. The probable mechanism of the Cfm PCD via α-HNPs and the degradation pathway was conducted. The validation of the suspension stability of the α-HNPs (-68.6 ± 11.8 mV) was determined using the zeta potential investigation test. XRD investigation was conducted after Cfm PCD showing an average crystallite size of 27.0 nm. XRD, TEM, SEM, EDX, and FT-IR analyses have been conducted for the α-HNPs before and after Cfm PCD confirming the high efficiency for the reusability of the current biocatalyst α-HNPs for further use. TEM results of the particle sizes of α-HNPs were found at 19.2 ± 4.4 and 20.6 ± 7.4 nm respectively before and after Cfm PCD. The efficiency of the Cfm PCD was found to be 99.1% after 6 h. High potent as an antibacterial agent of α-HNPs was investigated either α-HNPs alone or after its PCD activity against Cfm. The antibacterial activity revealed high sensitivity, especially toward Gram-positive species indicating its promising ability against pathogenic issues. Interestingly, Cfm@α-HNPs showed superior anti-proliferative activity as tested by MTT assay and were able to induce apoptosis in MCF7 and HepG2 cell lines using the flow cytometry technique at 20.7% and 17% respectively. Also, The IC50 of hydrogen peroxide scavenging was estimated and it was manifested that 635.8 and 665.6 μg/mL of α-HNPs before and after the PCD process of Cfm respectively.

Bioremediation and decontamination potentials of metallic nanoparticles loaded nanohybrid matrices - A review

The current nanotechnological advancements provide an astonishing insight to fabricate nanomaterials for nano-bioremediation purposes. Exciting characteristics possessed by hybrid matrices at the nanoscale knock endless opportunities to nano-remediate environmentally-related pollunanomaterials tants of emerging concern. Nanometals are considered among the oldest generation of the world has ever noticed. These tiny nanometals and nanometal oxides showed enormous potential in almost every extent of industrial and biotechnological domains, including their potential multipurpose approach to deal with water impurities. In this manuscript, we discussed their role in the diversity of water treatment technologies used to remove bacteria, viruses, heavy metals, pesticides, and organic impurities, providing an ample perspective on their recent advances in terms of their characteristics, attachment strategies, performance, and their scale-up challenges. Finally, we tried to explore their futuristic contribution to nano-remediate environmentally-related pollutants of emerging concern aiming to collect treated yet safe water that can be reused for multipurpose.

Evaluation of the UV/H2O2 system for treating natural water with a mixture of anthracene and benzo[a]pyrene at ultra-trace levels

The presence of polycyclic aromatic hydrocarbons, such as anthracene (AN) and benzo[a]pyrene (BaP), in water has become a problem of great concern due to the detrimental health effects caused to humans and living beings. In this work, the efficiency of the UV/H₂O₂ system for degrading the target compounds at ultra-trace levels in surface water has been evaluated. For this purpose, a previous optimization step using a face-centered central composite experimental design has been conducted, considering the effect of the UV-C irradiance and the initial concentration of H₂O₂. It was evidenced that under optimal operating conditions (11 mg L^-1 H₂O₂ and 0.63 mW cm^-2 irradiance), AN and BaP removal percentages were higher than 99.8%. Additionally, 69.3% of the organic matter, in terms of total organic carbon, was mineralized without the production of transformation by-products more harmful than the parent compounds. These findings demonstrate the oxidation capacity of the examined system in a natural matrix for degrading micropollutants that cannot be converted through conventional treatment processes. Consequently, new horizons are opened for the effective use of the UV/H₂O₂ system for drinking water production, providing the accomplishment of other regulated parameters related to water quality.

Photodegradation of naphthalene over Fe3O4 under visible light irradiation

Using FeCl3 and FeSO4 as precursors, Fe3O4 were prepared by co-precipitation method via FeCl3 and FeSO4 aqueous solutions successively added to NaOH solution. The sample was proved by X-ray powder diffraction, transmission electron microscope, ultraviolet-visible spectrophotometry and magnetic measurement. The results showed that the prepared Fe3O4 material was composed of an average diameter of about 15 nm particles and nano rods with well-crystallized magnetite and stronger superparamagnetic, getting a saturation magnetization of 49.5 emu g-1. This Fe3O4 material was found to be an effective catalyst for photodegradation of naphthalene with or without H2O2 under visible light irradiation, getting 81.1% and 74.3% degradation rate in these two cases, respectively. The degradation pathway in the absence and presence of H2O2 was analysed via measurement of the distribution of degradation products by GC-MS and adsorption of reactants on the surface of the catalyst by in situ DRIFTS spectra.

Degradation of UV-filter Benzophenon-3 in aqueous solution using TiO2 coated on quartz tubes

BACKGROUND

Benzophenone-3 (BP-3), one of the emerging pollutants, is commercially synthesized as UV filter used in cosmetics and other personal care products and its occurrence in the aquatic environment has widely been reported. The goal of this study was to enhance an AOP method for degradation of UV filter Benzophenone-3 in aqueous solutions.

METHOD

In this study, sol-gel method was applied to synthesis TiO₂ nanoparticles. Subsequently, the nanoparticles were successfully coated on quartz tubes. The synthesized catalyst was characterized using XRD, FE-SEM and EDX analysis. Then, the efficiency of photocatalytic process using TiO₂ coated quartz tubes for BP-3 degradation from synthetic and real aqueous solution was assessed.

RESULT

The optimum contact time and solution pH for the highest BP-3 degradation in the synthetic solution were found at 15 min and 10, respectively. The maximum degradation (98%) of BP-3 by photocatalytic process was observed at 1 mg/L initial BP-3 concentration using 225 cm² of catalyst surface area. Among the three applied kinetic models, the experimental data were found to follow the first-order equation more closely with the rate constant of 0.2, 0.048 and 0.035 1/min for 1, 3 and 5 mg/L of initial BP-3 concentration, respectively. In order to investigate the potential of this process for real effluent, the treatment of swimming pool water and wastewater treatment plant was examined and BP-3 degradation close to 88% and 32.1 was achieved, respectively.

CONCLUSION

Based on the obtained data, the photocatalytic process could successfully be applied for water treatment in swimming pools and other effluent containing BP-3 with low turbidity. The advantage of this study is that the synthesized catalyst can be used repeatedly needless to remove catalyst from the treated solution. In addition, AOP_s can effectively eliminate organic compounds in aqueous phase, rather than transferring pollutants into another phase. The limitation of this study is that in solution with high turbidity photocatalytic degradation can be hampered and pre- treatment is needed to reduce turbidity.

Bismuth vanadate-based semiconductor photocatalysts: a short critical review on the efficiency and the mechanism of photodegradation of organic pollutants

The number of publications on photocatalytic bismuth vanadate-based materials is constantly increasing. Indeed, bismuth vanadate is gaining stronger interest in the photochemical community since it is a solar-driven photocatalyst. However, the efficiency of BiVO₄-based photocatalyst under sunlight is questionable: in most of the studies investigating the photodegradation of organic pollutants, only few works identify the by-products and evaluate the real efficiency of BiVO₄-based materials. This short review aims to (i) present briefly the principles of photocatalysis and define the photocatalytic efficiency and (ii) discuss the formation of reactive species involved in the photocatalytic degradation process of pollutants and thus the corresponding photodegradation mechanism could be determined. All these points are developed in a comprehensive discussion by focusing especially on pure, doped, and composite BiVO₄. Therefore, this review exhibits a critical overview on different BiVO₄-based photocatalytic systems with their real efficiency. This is a necessary knowledge for potential implementation of BiVO₄ materials in environmental applications at larger scale than laboratory conditions.

Carbofuran degraded by iron-doped anatase: Weakening the cholinesterase inhibitory activity in the photoproducts mixture

Carbofuran is a toxic carbamate pesticide, and its use has increased in recent years. While marketing information indicates stability in different chemical media, carbofuran exhibits relative photolability. The aim of this research was to decompose carbofuran and to identify the photoproducts achieved when two different doped titania photocatalysts were employed under UV irradiation. The iron-doped TiO₂ materials were obtained (a) via a hydrothermal method and (b) by an ultrasound-assisted sol-gel method. The precursors were TiOSO₄⋅xH₂O and Fe₃(NO₃)·9H₂O. X-ray studies confirmed that the anatase phase of the iron-doped TiO₂ resulted from the two preparation methods. The photocatalytic performance of the prepared materials was monitored by LC/ESI-QTOF-MS, enabling the identification of photoproducts: oxo-carbamates, hydroxylated benzofuranes, a carboxamide, and one amine. By using the iron-doped TiO₂ materials, 2,2-dimethyl-2,3-dihydrobenzofuran-3,7-diol was the most abundant photoproduct, and N,2,2-trimethyl-2,3-dihydrobenzofuran-7-amine was the only compound that had not been previously reported in the photolysis and photocatalysis of carbofuran. The product 3-hydroxy carbofuran, a cholinesterase inhibitor, was quantified and was found to be transformed into compounds that lack this inhibitive property.

Carbofuran removal in continuous-photocatalytic reactor: Reactor optimization, rate-constant determination and carbofuran degradation pathway analysis

Carbofuran (CBF) removal in a continuous-flow photocatalytic reactor with granular activated carbon supported titanium dioxide (GAC-TiO₂) catalyst was investigated. The effects of feed flow rate, TiO₂ concentration and addition of supplementary oxidants on CBF removal were investigated. The central composite design (CCD) was used to design the experiments and to estimate the effects of feed flow rate and TiO₂ concentration on CBF removal. The outcome of CCD experiments demonstrated that reactor performance was influenced mainly by feed flow rate compared to TiO₂ concentration. A second-order polynomial model developed based on CCD experiments fitted the experimental data with good correlation (R² ∼ 0.964). The addition of 1 mL min^-1 hydrogen peroxide has shown complete CBF degradation and 76% chemical oxygen demand removal under the following operating conditions of CBF ∼50 mg L^-1, TiO₂ ∼5 mg L^-1 and feed flow rate ∼82.5 mL min^-1. Rate constant of the photodegradation process was also calculated by applying the kinetic data in pseudo-first-order kinetics. Four major degradation intermediates of CBF were identified using GC-MS analysis. As a whole, the reactor system and GAC-TiO₂ catalyst used could be constructive in cost-effective CBF removal with no impact to receiving environment through getaway of photocatalyst.

The photocatalytic degradation of carbofuran and Furadan 35-ST: the influence of inert ingredients

A comparative study on photocatalytic degradation of the pesticide carbofuran and its commercial product Furadan 35-ST in an aqueous suspension of ZnO, irradiated by long-wave light (315-400 nm), is presented in this study. In order to assess the effects of inert ingredients present in the commercial product Furadan 35-ST, non-competitive and competitive adsorption and kinetic studies of carbofuran degradation processes were conducted. A higher photochemical degradation rate was found for pure carbofuran in comparison to a two-component system, carbofuran and single addition of ingredients at appropriate concentrations, and the commercial product Furadan 35-ST. The overall effect of inert ingredients was evaluated from a competitive study using the model system of Furadan 35-ST. The results of a mineralization study, obtained by ion chromatography (IC) and total organic carbon (TOC) analyses, revealed the formation of acetate, oxalate, and formate ions. Photodegradation products of carbofuran, three of them detected for the first time, were identified based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) results, and their photodegradation pathways were proposed.

Selecting the best AOP for isoxazolyl penicillins degradation as a function of water characteristics: Effects of pH, chemical nature of additives and pollutant concentration

To provide new insights toward the selection of the most suitable AOP for isoxazolyl penicillins elimination, the degradation of dicloxacillin, a isoxazolyl penicillin model, was studied using different advanced oxidation processes (AOPs): ultrasound (US), photo-Fenton (UV/H₂O₂/Fe²⁺) and TiO₂ photocatalysis (UV/TiO₂). Although all processes achieved total removal of the antibiotic and antimicrobial activity, and increased the biodegradability level of the solutions, significant differences concerning the mineralization extend, the pH of the solution, the pollutant concentration and the chemical nature of additives were found. UV/TiO₂ reached almost complete mineralization; while ∼10% mineralization was obtained for UV/H₂O₂/Fe²⁺ and practically zero for US. Effect of initial pH, mineral natural water and the presence of organic (glucose, 2-propanol and oxalic acid) were then investigated. UV/H₂O₂/Fe²⁺ and US processes were improved in acidic media, while natural pH favored UV/TiO₂ system. According to both the nature of the added organic compound and the process, inhibition, no effect or enhancement of the degradation rate was observed. The degradation in natural mineral water showed contrasting results according to the antibiotic concentration: US process was enhanced at low concentration of dicloxacillin followed by detrimental effects at high substrate concentrations. A contrary effect was observed during photo-Fenton, while UV/TiO₂ was inhibited in all of cases. Finally, a schema illustrating the enhancement or inhibiting effects of water matrix is proposed as a tool for selecting the best process for isoxazolyl penicillins degradation.

Methylparaben removal using heterogeneous photocatalysis: effect of operational parameters and mineralization/biodegradability studies

Methylparaben (MePB) is an organic compound employed mainly in the manufacture of different personal care products. However, it has been recently listed as a potential endocrine disrupter chemical. Therefore, the main objective of this work was to evaluate the degradation of MePB in aqueous solutions using heterogeneous photocatalysis with TiO₂ and hydrogen peroxide. In this way, effects of pH and the initial concentrations of catalyst, H₂O₂, and pollutant on treatment were analyzed. A face centered, central composite design was used for determination of the influence of each parameter in the process and the conditions under which the pollutant suffers the highest rates of degradation were selected. In general, results indicate that combination TiO₂/H₂O₂/light irradiation leads to ∼90 % of substrate removal after 30 min of reaction and that hydroxyl free radicals are the main specie responsible for organic matter elimination. Finally, in terms of mineralization and biodegradability, experimental results indicated that part of the organic matter was transformed into CO₂ and water and the photo-treatment promoted an increase in samples biodegradability.

Photocatalytic degradation of carbofuran by TiO2-coated activated carbon: Model for kinetic, electrical energy per order and economic analysis

The photocatalytic removal of carbofuran (CBF) from aqueous solution in the presence of granular activated carbon supported TiO2 (GAC-TiO2) catalyst was investigated under batch-mode experiments. The presence of GAC enhanced the photocatalytic efficiency of the TiO2 catalyst. Experiments were conducted at different concentrations of CBF to clarify the dependence of apparent rate constant (kapp) in the pseudo first-order kinetics on CBF photodegradation. The general relationship between the adsorption equilibrium constant (K) and reaction rate constant (kr) were explained by using the modified Langmuir-Hinshelwood (L-H) model. From the observed kinetics, it was observed that the surface reaction was the rate limiting step in the GAC-TiO2 catalyzed photodegradation of CBF. The values of K and kr for this pseudo first-order reaction were found to be 0.1942 L  mg(-1) and 1.51 mg L(-1) min(-1), respectively. In addition, the dependence of kapp on the half-life time was determined by calculating the electrical energy per order experimentally (EEO experimental) and also by modeling (EEO model). The batch-mode experimental outcomes revealed the possibility of 100% CBF removal (under optimized conditions and at an initial concentration of 50 mg L(-1) and 100 mg L(-1)) at a contact time of 90 min and 120 min, respectively. Both L-H kinetic model and EEO model fitted well with the batch-mode experimental data and also elucidated successfully the phenomena of photocatalytic degradation in the presence of GAC-TiO2 catalyst.

Heterogeneous photocatalytic degradation of the endocrine-disrupting chemical Benzophenone-3: Parameters optimization and by-products identification

Benzophenone-3 (BP3) is one of the most used UV filters. Its disruptive effect on the endocrine system of different living beings has been demonstrated by several research groups. Present work addresses on a photocatalytic degradation of BP3 using particles of titanium dioxide in aqueous solutions considering the effect of operating parameters such as pH, catalyst and pollutant initial concentrations, and the presence of hydrogen peroxide, acetonitrile and isopropanol in the solution. In this way, a face centered, central composite design was carried out for the identification of significant factors or interactions that allow the determination of the conditions under which the pollutant suffers the highest rates of degradation. A solution initial pH of 9.0, a TiO2 concentration of 1.184 g L(-1) and an H2O2 concentration of 128.069 mg L(-1) were established as the optimal conditions for the substrate removal. In aqueous solutions and low concentrations of the pollutant (<2 mg L(-1)) photocatalytic degradation followed a pseudo-first order kinetics. After 300 min of treatment, ∼67% of the dissolved organic carbon was removed, which together with a reduction in toxicity and an increase in biodegradability confirmed that photocatalysis with TiO2 is a potential method to remove BP3 from water. Additionally, tests using acetonitrile as solvent and isopropanol as hydroxyl radical (OH(.)) scavenger suggested that, OH(.) was the main agent responsible of substrate degradation. Finally, ten process by-products were identified and a degradation route was proposed.

Improved WO3 photocatalytic efficiency using ZrO2 and Ru for the degradation of carbofuran and ampicillin

The photocatalytic degradation of carbofuran (pesticide) and ampicillin (pharmaceutical) using synthesized WO3/ZrO2 nanoparticles under simulated solar light was investigated. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectra analyses were used to characterize the prepared catalysts. The optimum ratio of WO3 to ZrO2 was determined to be 1:1 for the degradation of both contaminants. The degradation of carbofuran and ampicillin by WO3/ZrO2 after 240 min of irradiation was 100% and 96%, respectively. Ruthenium (Ru) was employed as an additive to WO3/ZrO2 to enhance the photocatalytic degradation rate. Ru/WO3/ZrO2 exhibited faster degradation rates than WO3/ZrO2. Furthermore, 100% and 97% degradation of carbofuran and ampicillin, respectively, was achieved using Ru/WO3/ZrO2 after 180 min of irradiation. The durability of the catalyst was investigated by reusing the same suspended catalyst, which achieved 92% of its initial efficiency. The photocatalytic degradation of ampicillin and carbofuran followed pseudo-first order kinetics according to the Langmuir-Hinshelwood model.

Simple Response Surface Methodology: Investigation on Advance Photocatalytic Oxidation of 4-Chlorophenoxyacetic Acid Using UV-Active ZnO Photocatalyst

The performance of advance photocatalytic degradation of 4-chlorophenoxyacetic acid (4-CPA) strongly depends on photocatalyst dosage, initial concentration and initial pH. In the present study, a simple response surface methodology (RSM) was applied to investigate the interaction between these three independent factors. Thus, the photocatalytic degradation of 4-CPA in aqueous medium assisted by ultraviolet-active ZnO photocatalyst was systematically investigated. This study aims to determine the optimum processing parameters to maximize 4-CPA degradation. Based on the results obtained, it was found that a maximum of 91% of 4-CPA was successfully degraded under optimal conditions (0.02 g ZnO dosage, 20.00 mg/L of 4-CPA and pH 7.71). All the experimental data showed good agreement with the predicted results obtained from statistical analysis.

Evaluation of water matrix effects, experimental parameters, and the degradation pathway during the TiO2 photocatalytical treatment of the antibiotic dicloxacillin

The photocalytic degradation of dicloxacillin (DXC) using TiO2 was studied in synthetic and natural waters. The degradation route and the effect of different experimental variables such as pH, applied power, and the initial concentrations of DXC and the catalyst were investigated. The best performances were achieved at a natural pH 5.8 and using 2.0 g L(-1) of TiO2 with 150 W of applied power. The photodegradation process followed Langmuir-Hinshelwood kinetics. The water matrix effect was evaluated in terms of degradation efficiency in the presence of organic compounds (oxalic acid, glucose), Fe(2+) ion and natural water. An increase in degradation was observed when ferrous ion was part of the solution, but the process was inhibited with all evaluated organic compounds. Similarly, inhibition was observed when natural water was used instead of distilled water. The extent of degradation of the process was evaluated following the evolution of chemical oxygen demand (COD), antimicrobial activity (AA), total organic carbon (TOC) and biochemical oxygen demand (BOD5). Total removal of DXC was achieved after 120 min of treatment and 95% mineralization was observed after 480 min of treatment. Additionally, the total removal of antimicrobial activity and a high level of biodegradability were observed after the photocalytical system had been operating for 240 min.

The investigation of the LED-activated FeFNS-TiO2 nanocatalyst for photocatalytic degradation and mineralization of organophosphate pesticides in water

This study evaluated the preparation and characterization of an efficient doped TiO2 as a novel catalyst for degradation of diazinon model pesticide using LED-activated photocatalysis. TiO2 was doped using N, NS, FeNS, and FeFNS. The FeFNS-doped TiO2 showed the highest catalytic activity in LED/photocatalysis. FeFNS-doped TiO2 is a mesoporous nanocrystal powder with a mean pore diameter of 10.2 nm, a specific surface area of 104.4 m(2)/g and a crystallite size of 6.7 nm. LED/photocatalysis using FeFNS-doped TiO2 improved diazinon degradation by 52.3% over that of as-made plain TiO2 at an optimum solution pH of 7. The diazinon degradation in LED/photocatalysis using FeFNS-doped TiO2 increased from 44.8% to 96.3% when the catalyst concentration increased from 25% to 300%at a reaction time of 100 min. The degradation and mineralization of diazinon during LED/photocatalysis with FeFNS-doped TiO2 catalyst followed the pseudo-first-order reaction model with the rate constants of 0.973 h(-1) and 0.541 h(-1), respectively. The FeFNS-doped TiO2 was found to be an efficient catalyst that was photoactivated using UV-LED lamps. LED/photocatalysis with FeFNS-doped TiO2 catalyst is a promising alternative to conventional UV/TiO2photocatalysis for producing free OH radicals for use in the degradation and mineralization of water toxic contaminants.

Removal of polycyclic aromatic hydrocarbons in aqueous environment by chemical treatments: a review

Due to their carcinogenic, mutagenic and teratogenic potential, the removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous environment using physical, biological and chemical processes has been studied by several researchers. This paper reviews the current state of knowledge concerning PAHs including their physico-chemical properties, input sources, occurrence, adverse effects and conventional and alternative chemical processes applied for their removal from water. The mechanisms and reactions involved in each treatment method are reported, and the effects of various variables on the PAH degradation rate as well as the extent of degradation are also discussed. Extensive literature analysis has shown that an effective way to perform the conversion and mineralization of this type of substances is the application of advanced oxidation processes (AOPs). Furthermore, combined processes, particularly AOPs coupled with biological treatments, seem to be one of the best solutions for the treatment of effluents containing PAHs.

Degradation of the pesticide carbofuran on clay and soil surfaces upon sunlight exposure

In the present study, the photolysis of carbofuran has been undertaken under sunlight conditions and at the surface of model supports such as clay films and different soils collected from two different sites in Morocco (Tirs and Dahs). In all conditions, an efficient degradation occurred owing to direct light absorption and also to photoinduced processes involving either clays or natural organic matter moities. On kaolin films, the photodegradation kinetics appears to follow a first-order process that clearly depends on the film thickness. The diffusion of carbofuran from the lower part to the illuminated surface was found to be negligible when compared to the photolysis process within the range of 20-70 μm. Thus, the photolysis rate constant at the surface of the solid support, k (0), was evaluated to be 7.0 × 10(-3) min(-1). Under these experimental conditions, the quantum yield was found equal to 2.1 × 10(-4). On soil surfaces, the disappearance rate constant was mainly attributed to photoinduced processes arising from natural organic matter. From the analytical point of view, the products were formed through (1) hydroxylation on the aromatic ring, (2) homolytic scission of the carbamate C-O bond leading to radical species formation, and (3) photohydrolysis of the carbamate C-O bond.

Photocatalytic degradation of carbofuran in TiO2 aqueous solution: kinetics using design of experiments and mechanism by HPLC/MS/MS

The photocatalytic degradation kinetics of carbofuran was optimized by central composite design based on response surface methodology for the first time. Three variables, TiO2 concentration, initial pH value and the concentration of carbofuran, were selected to determine the dependence of degradation efficiencies on independent variables. Response surface methodology modeling results indicated that the degradation efficiency of carbofuran was highly affected by the initial pH value and the concentration of carbofuran. Then nine degradation intermediates were detected by HPLC/MS/MS. The Frontier Electron Densities of carbofuran were calculated to predict the active sites on carbofuran attacked by hydroxyl radicals and photoholes. Point charges were used to elucidate the chemisorption pattern on TiO2 catalysts during the photocatalytic process. By combining the experimental results and calculation data, the photocatalytic degradation pathways of carbofuran were proposed, including the addition of hydroxyl radicals and the cleavage of the carbamate side chain.

Solar photo-Fenton treatment of carbofuran: analysis of mineralization, toxicity, and organic by-products

The degradation of the pesticide carbofuran (CBF) using solar photo-Fenton treatment, at both the laboratory and the pilot scale, was evaluated. At the laboratory scale, in a suntest reactor, the Fe(2+) concentration and H(2)O(2) concentration were evaluated and optimized using the surface response methodology and the Pareto diagram. Under optimal conditions experiments were performed to evaluate the evolution of the substrate removal, oxidation, subsequent mineralization, toxicity and the formation of chloride ions during the treatment. The analysis and evolution of five CBF by-products as well as several control and reactivity tests at the density functional theory level were used to depict a general scheme of the main degradation pathway of CBF via the photo-Fenton system. Finally, at the pilot scale, a sample of the commercial CBF product Furadan was eliminated after 420 min by the photo-Fenton system using direct sunlight. Under these conditions, after 900 min 89% of toxicity (1/E(50) on Vibrio fischeri bacteria), 97% of chemical oxygen demand, and 90% of dissolved organic carbon were removed.