Photodegradation In Water Research Articles

Application of machine learning models to improve the prediction of pesticide photodegradation in water by ZnO-based photocatalysts

Pesticide pollution has been posing a significant risk to human and ecosystems, and photocatalysis is widely applied for the degradation of pesticides. Machine learning (ML) emerges as a powerful method for modeling complex water treatment processes. For the first time, this study developed novel ML models that improved the estimation of the photocatalytic degradation of various pesticides using ZnO-based photocatalysts. The input parameters encompassed the source of light, mass proportion of dopants to Zn, initial pesticide concentration (C0), pH of the solution, catalyst dosage and irradiation time. Additionally, physicochemical properties such as the molecular weight of the dopants and pesticides, as well as the water solubility of both dopants and pesticides, were considered. Notably, the numerical data were extracted from the literature via relevant tables (directly) or graphs (indirectly) using the web-based tool WebPlotDigitizer. Four ML models including multi-layer perceptron artificial neural network (MLP-ANN), particle swarm optimization-adaptive neuro fuzzy inference system (PSO-ANFIS), radial basis function (RBF), and coupled simulated annealing-least squares support vector machine (CSA-LSSVM) were developed. In comparison, RBF showed the best accuracy of modeling among all models, with the highest determination coefficient (R2) of 0.978 and average absolute relative deviation (AARD) of 4.80%. RBF model was effective in estimating the photocatalytic degradation of pesticides except for 2-chlorophenol, triclopyr and lambda-cyhalothrin, where CSA-LSSVM model demonstrated superior performance. Dichlorvos was completely degraded by ZnO photocatalyst under visible light. The sensitivity analysis by relevancy factor exhibited that light irradiation time and initial pesticide concentration were the most important parameters influencing photocatalytic degradation of pesticides positively and negatively, respectively. The new ML models provide a powerful tool for predicting pesticide degradation in wastewater treatment, which will reduce photochemical experiments and promote sustainable development.

One-pot synthesis of BiSCl–Bi6.88S8·64Cl3.36 nanorods for rhodamine B photodegradation in water

In the domain of water treatment, photocatalytic degradation presents a compelling approach. However, the quest for photocatalysts that exhibit superior solar energy absorption and conversion remains a challenge. We explore rod-shaped bismuth-rich chalcohalide photocatalyst BiSCl–Bi6.88S8·64Cl3.36 by simple temperature control and demonstrate the proficiency in degrading organic pollution under visible light. BiSCl–Bi6.88S8.64Cl3.36 nanorods manifest a composition-tailored band gap, effectively spanning the visible spectrum. Remarkably, in the absence of cocatalysts and sacrificial agents, BiSCl–Bi6.88S8·64Cl3.36 exhibit exceptional photocatalytic degradation rate of 99.8%, which is comparable to that of BiSBr (98.6%). Moreover, the photodegradation rate of BiSCl–Bi6.88S8·64Cl3.36 (0.091 min−1) is higher than that of BiSBr (0.048 min−1). The rate position it among the most effective known photocatalysts, with the generation of superoxide anion radicals (•O2−) and photogenerated holes (h+) as the primary active species. Notably, the enhanced photocatalytic activity of BiSCl–Bi6.88S8·64Cl3.36 is attributed to the high number of Bi centers and the higher electronegativity, which induces a more polar crystal structure.

Titanium dioxide nanoparticles embedded in assembled dipeptide hydrogels for microfluidic photodegradation

Dipeptides can be self-assembled via non-covalent bonds towards functional nanostructures for diverse applications in nanotechnology. Here, we introduce a convenient microfluidics-guided dipeptide design as a platform for photodegradation of contaminants in water. Titanium dioxide (TiO2) nanoparticles (NPs) are chosen as photocatalysts due to their vastly studied properties. By using a well-defined microchannel architecture, the dipeptide N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) and TiO2 NPs are efficiently mixed leading to a self-assembled Fmoc-FF hydrogel with embedded TiO2. Owing to shear-thinning and rapid self-healing of Fmoc-FF hydrogels, we can transfer and inject Fmoc-FF/TiO2 hydrogels into any other microdevice for specific applications, where these low-molecular-weight-gelator- (LMWG-)based Fmoc-FF hydrogels fill out the microchannel volume. Different morphologies of Fmoc-FF/TiO2 hydrogels are obtained by simple concentration screening of TiO2 NPs and Fmoc-FF. Owing to the density of the three-dimensionally twined Fmoc-FF nanofibers, solutions swelling the dipeptide hydrogel can be exchanged without leaching out TiO2 NPs. By further analysis, our hydrogel-filled flow cell can be employed for continuous-flow photodegradation in water under light irradiation. Especially, compared to the TiO2 NPs suspension, Fmoc-FF/TiO2 hydrogels with relatively low concentrations of TiO2 exhibit enhanced photodegradation capabilities due to better dispersion of nanoparticles. Such strategy provides a versatile platform for embedment of small inorganic catalysts or enzymes for (bio-)chemical conversion of solutes passing through the hydrogel network.

DOM optical parameters as a tool to understand degradation of phenolic contaminants of emerging concern

Composition and source of dissolved organic matter (DOM) in water influence the rate of production of reactive intermediates (RIs), affecting the photodegradation of phenolic contaminants of emerging concern (PhCECs). However, this relationship has not been fully quantified. Here, for the first time, we propose a mechanism for photodegradation of a surrogate of PhCECs, p-cresol, in different DOM standard solutions under simulated sunlight irradiation. More importantly, the correlation of DOM optical parameters and p-cresol photodegradation kinetic parameters was determined by Pearson correlation. Results showed that indirect photodegradation was the only degradation pathway for p-cresol, mainly through reaction with excited triplet state of dissolved organic matter (3DOM*). Singlet oxygen (1O2) and hydroxyl radical (•OH) hindered degradation of p-cresol by decreasing the steady state concentration of 3DOM*. Moreover, less aromatic and smaller molecular size DOM showed higher steady-state concentration and quantum yield of 1O2, and 3DOM*, resulting in faster p-cresol photodegradation. Finally, 7 out of 8 optical parameters showed strong correlation with the p-cresol photodegradation rate constant. The mechanism and correlations found are a potential tool to predict PhCECs photodegradation in water using DOM optical parameters.

First insights into 6PPD-quinone formation from 6PPD photodegradation in water environment

p-Phenylenediamines (PPDs), an important type of rubber antioxidants, have received little study on their environmental fate, particularly for their vital photodegradation process in water environment. Accordingly, N-(1,3-dimethylbutyl)-N′-phenyl-1,4-phenylenediamine (6PPD), as a representative of PPDs, was investigated experimentally and theoretically for its photodegradation in water. Rapid photodegradation occurred when 6PPD was exposed to illumination especially UV region irradiation. Under acidic conditions, the photodegradation of 6PPD accelerated mainly due to the increased absorption of long wavelength irradiation by ionized 6PPD. Nine photodegradation products (e.g., 6PPD-quinone (6PPDQ)) of 6PPD were identified by an ultra-performance liquid chromatography QTOF mass spectrometry. Molar yields of photoproducts such as 6PPDQ, aniline, 4-aminodiphenylamine, and 4-hydroxydiphenylamine were 0.03 ± 0.00, 0.10 ± 0.01, 0.03 ± 0.02, and 0.08 ± 0.01, respectively. Mechanisms involved in 6PPD photodegradation include photoexcitation, direct photolysis, self-sensitized photodegradation, and 1O2 oxidation, as demonstrated by electron paramagnetic resonance (EPR) analysis, scavenging experiments, and the time-dependent density functional theory (TD-DFT). Notably, the toxicity of the reaction solution formed during the photodegradation of 6PPD was increased by the formation of highly toxic products (e.g., 6PPDQ). This study provides the first explanation for photodegradation mechanisms of 6PPD and confirms the pathway of 6PPDQ produced by the photoreaction in water environment.

Spinach-derived boron-doped g-C3N4/TiO2 composites for efficient photo-degradation of methylene blue dye

Green synthesis of nanoparticles can be beneficial due to their low toxicity, cost-effectiveness, and environment-friendliness. Its synthesis involves the use of eco-friendly and biodegradable materials such as plant extracts, natural products, and microorganisms to reduce the negative environmental impacts of traditional nanoparticle synthesis methods. Herein, Spinacia oleracea leaves are used as a boron source, and a visible light active photo-catalyst is produced. The effect of Co-Catalyst Boron in Graphitic carbon nitride based nanocomposites for methylene blue dye photo-degradation in water is examined. Titanium dioxide (TiO2) was activated by changing the hydrogen potential value while utilizing a typical orange dye as a sensitizer. The graphitic carbon nitride/TiO2 nanocomposites were synthesized through a hydrothermal technique. To improve their performance, Boron used as a co-catalyst and B-doped g-C3N4/TiO2nanocomposites prepared through wet chemical co-percipitate mathod. UV–visible spectroscopy, SEM and FTIR spectroscopy were used to analyze the photocatalyst and boron-doped composites in detail. The photocatalytic performance of pristine photocatalyst CNTx (x = 2%,4%,6%,8%) and B-doped CNTx composites were examined for Methylene Blue degradation in the presence of a light source. The spectroscopy analysis showed that B-doped g-C3N4/TiO2 -8% nano-composites performed better than all other synthesized pristine catalysts and composites in this research. This research has demonstrated that B-doped g-C3N4/TiO2 composites can provide an ideal solution for treating polluted water using visible light as a source to activate these photocatalysts.

ZnS-doped TiO2 photocatalysts for 4-chlorophenol photodegradation in water

ZnS-doped TiO2 photocatalysts for 4-chlorophenol photodegradation in water

Synthesis and Characterization of Poly(2-vinylpyridine) and Poly(4-vinylpyridine) with Metal Oxide (TiO2, ZnO) Films for the Photocatalytic Degradation of Methyl Orange and Benzoic Acid.

In this study, composite material films of pyridine-based polymer and metal oxides (ZnO and TiO2) were successfully deposited by spin coating method for environmental remediation. Firstly, the polymers poly(2-vinylpyridine) P(2-VP), and poly(4-vinylpyridine) P(4-VP) were synthesized via solution polymerization. The analysis by grazing incidence X-ray diffraction (GIXRD) reveals semicrystalline nature and scanning electron microscopy (SEM) indicates that the poly(vinylpyridines) clusters of particles were observed on the surface of the films. It was also shown that the morphology of composite materials is completely dependent on the chemical nature of the oxide. In the case of P(2-VP)-TiO2 and P(4-VP)-TiO2, some channels or pathways of TiO2 on the surface of films were observed. However, the surface morphology of the polymer composites formulated with ZnO shows a homogeneous distribution in P(2-VP) and P(4-VP) matrix. The effectiveness of the composite materials in the photodegradation of methyl orange (MO) was evaluated by photocatalysis. According to the results, the P(4-VP)-ZnO composite exhibited the highest photodegradation of MO, allowing the separation of photogenerated species required for the photocatalytic reaction. The P(4-VP)-ZnO composite was also tested in benzoic acid (BA) photodegradation in water. The presence of some scavengers in the reaction system reveals that hydroxyl radicals (OH•), superoxide radicals (O2-•) and holes (h+) are responsible for the BA reduction by photocatalysis.

Synergistic Effect of NiO-Ga2O2-Graphene Heterostructures on Congo Red Photodegradation in Water

We studied the effect of the mixed phase of nickel oxide–gallium oxide–graphene (NiO-Ga2O2/G) heterostructure nanocomposite on the photocatalytic degradation of Congo red dye. The effect was investigated based on NiO-Ga2O2 junction, NiO-graphene, and Ga2O2-graphene contacts. The laser-induced graphene was embedded into NiO and NiO-Ga2O2. Raman spectra confirmed the fabrication of disordered graphene and the mixed phase between the oxides and graphene. HRTEM showed that very fine nanoparticles for both NiO and Ga2O2 with a size of ~7–10 nm were synthesized. Elemental compositional expressed the formation mixed phase. The effect of graphene content was investigated at 2 and 10% wt with NiO and the heterojunction of NiO-Ga2O2. The photocurrent studies was measured of these nanocomposite film deposited on two interdigitated gold electrodes, biased by 5.0 V and irradiated by the UV source. The results of photocatalysis measurements indicated an improvement occurred upon the heterojunction between Ga2O2 and NiO, however, a dramatic improvement was observed with the addition of graphene of 10%. The results expressed that the ternary phase of p-NiO/n-Ga2O2/graphene is promising in the photocatalytic application toward Congo red decomposition.

Optical properties and visible-light-driven photocatalytic activity of Na2Mn2(MoO4)3

In this paper, Na2Mn2(MoO4)3 doubgyle molybdate was prepared by sol-gel method to investigate the structural, morphological and optical properties. X-ray diffraction analysis showed that Na2Mn2(MoO4)3 crystallizes in the triclinic system in the P1¯ group. The composition and morphology of the compound were checked by energy dispersive spectroscopy coupled with scanning electron microscope. Optical properties were analyzed by UV–Vis diffuse reflectance spectroscopy. The photocatalytic properties were evaluated by the degradation of methylene blue under natural sunlight and compared to Xe and UV lamps. The highest photodegradation efficiency (85.3%) was obtained for solar irradiation, therefore, Na2Mn2(MoO4)3 can be a potential photocatalyst for the removal of dye wastewater pollution driven by visible-light. The proposed mechanism of photodegradation in water involves creation of hydroxyl radicals and superoxide anions that attack the methylene blue molecules and decompose it to carbon dioxide and water.

Cobalt doping of titanium oxide nanoparticles for atenolol photodegradation in water.

Cobalt-doped TiO2 nanoparticles were prepared and characterized by FT-IR, TEM, SEM, and XRD. The surface morphology was sphere-shaped with ~ 26.46nm of the size of the nanoparticles. Ninety percent atenolol photodegradation was obtained with 15mg/L concentration, 40min stirring time, 2 pH, 2.0g/L dosage of nanoparticles, 200.0nm irradiation UV wavelength, and hydrogen peroxide amount 2.0mL/L at 30°C temp. Atenolol photodegradation conformed the first-order kinetics with a mechanism comprising atenolol sorption on the doped TiO2 nanoparticles and its degradation in UV irradiation. Hole (h+) and electron (e-) pairs are produced by doped TiO2 nanoparticles, creating hydroxyl free radicals and superoxide oxygen anions. These species break down atenolol.

Effects of surfactants on the morphology and properties of TiO2

TiO2 nanoparticles with controllable morphology perform well in both physical and chemical properties, which have great significance in photocatalytic degradation of wastewater and photodegradation of water. In this study, TiO2 was prepared by solvothermal method with tetrabutyl titanate as titanium source, acetic acid as solvent and surfactant as additive. The effects of single and mixed surfactants, such as cetyltrimethylammonium bromide (CTAB), polyethylene glycol (PEG) and carboxamide, on the microstructure of TiO2 were systematically studied. The results showed that the prepared TiO2 was anatase phase. It clearly demonstrated the procedure how the morphology and size of TiO2 were influenced by surfactant. In the reaction system, when carboxamide was added to TiO2, CTAB or PEG, TiO2 nanocrystals gathered to form rod, cluster or similar ellipse, respectively. When two or more different surfactants were added to the system simultaneously, the morphology of TiO2 could be cauliflower-like, spherical and three-dimensional flower-like structures formed by the directional aggregation of nanocrystals due to the coordination between the surfactants. The photocatalytic properties of methyl orange were investigated under UV irradiation. The results showed that the photocatalytic properties of cauliflower-like structures, spherical structures and three-dimensional flower-like structures formed by the directional aggregation of nanocrystals were better than those of commercial Degussa P25. TiO2 nanoparticles with three-dimensional flower-like structures exhibited good photocatalytic performance, with the degradation ratio of methyl orange 94% under simulated irradiation for 60 min.

Parameters affecting carbofuran photocatalytic degradation in water using ZnO nanoparticles

AbstractCarbofuran photodegradation in water using zinc oxide nanoparticles as a catalyst was examined as well as some parameters influencing its percentage degradation rate such as zinc oxide load, initial concentration of carbofuran, the temperature of the reaction, the initial pH of the solution, and doping of zinc oxide nanoparticles with 5% (w:w) silver. Zinc oxide and Ag‐doped zinc oxide nanoparticles were produced using solvothermal and photoreduction methods, respectively, and silver doping effects on the structural, optical, and photocatalytic properties of zinc oxide nanoparticles were investigated using XRD, UV‐VIS spectrophotometer, TEM, SEM, SEM/EDX, and FTIR. The average diameter of the synthesized samples was 26.6, 30.55 nm for undoped zinc oxide and Ag‐doped zinc oxide, respectively. Zinc oxide doping with silver did not change the shape of the zinc oxide crystal, but decreased the reflection in the visible region, as well as the energy of the bandgap, and increased the zinc oxide photocatalytic activity.

Facile Ge/GR nanocubes synthesis and application for Sudan I photodegradation in water

In this work, highly uniform cubic germanium/husk-derived graphene nanocomposites (Ge/GR nanocubes) were synthesized via facile chemical methods. The structure and composition of the prepared Ge/GR nanocubes were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) etc., confirming a homogeneous distribution of Ge nanocubes (30–90 nm in size) on few-layered graphene nanosheets. Further investigations showed that the prepared novel Ge/GR nanocubes could combine both photocatalytical advantages of Ge nanocubes and graphene nanosheets for Sudan I purification with optimal removal efficiency of 98.1% in wide concentration range (0.25–4.0 mg/mL) at mild conditions. The prepared high active photocatalyst can be used for five consecutive runs. By using husk-derived graphite microcrystalline as the starting material of graphene, the cost of the Ge/GR nanocubes was obvious decreased, which fosters it a high active, low cost and durable candidate for azo dye removal in water.

Enhanced Photodegradation of Extracellular Antibiotic Resistance Genes by Dissolved Organic Matter Photosensitization.

Extracellular antibiotic resistance genes (eARGs) contribute to antibiotic resistance, and as such, they pose a serious threat to human health. eARGs, regarded as an emerging contaminant, have been widely detected in various bodies of water. Degradation greatly weakens their distribution potential and environmental risks. Dissolved organic matter (DOM), mainly consisted of humic substances, carbohydrates, and organic acids, is ubiquitous in diverse waters and significantly affects the degradation of coexisting contaminants. However, the photodegradation of eARGs in natural water, especially regarding the roles of DOM in this process, remains unknown. Herein, we investigated the eARGs photodegradation in waters with and without DOM. Illumination has been found to effectively photodegrade eARGs, and this process was significantly enhanced by DOM. Further experiments revealed that photosensitization of DOM produced hydroxyl radicals (•OH) to enhance plasmid strand breaks and produced singlet oxygen (1O2) to accelerate the guanine oxidation, which in turn promoted the photodegradation of plasmid-carried eARGs. Transformation assays indicated that eARGs transformation efficiencies were reduced after their photodegradation. The presence of DOM accelerated the decreases of eARGs transformation efficiencies under illumination. DOM concentration and some ions (e.g., NO3-, NO2-, HCO3-, Br-, and Fe3+) affected •OH or 1O2 levels, further influencing the photodegradation of eARGs. Overall, eARGs photodegradation in aquatic environments is a crucial process both in the reduction of eARGs concentrations and in transformation efficiencies. This work facilitated us to better understand the fate of eARGs in waters.

Organotin Release from Polyvinyl Chloride Microplastics and Concurrent Photodegradation in Water: Impacts from Salinity, Dissolved Organic Matter, and Light Exposure

Photochemical weathering leads to degradation of microplastics and releases chemical additives, polymeric fragments, and/or byproducts. This study evaluated the release kinetics of organotin compounds (OTCs) from three different sized (10-300 μm) polyvinyl chloride (PVC) microplastics under UV- and visible light irradiation. Four OTCs, dimethyltin (DMT), monomethyltin (MMT), dibutyltin (DBT), and monobutyltin (MBT), were found to release from PVC particles after 24 h leaching in darkness ranging from 2 to 20 μg·g-PVC-1. Under UV/visible light irradiation, only DMT and DBT were detectable, whereas MMT and MBT were not detected due to rapid photodegradation. The total tin concentrations (including organic and inorganic tins) in the aqueous phase monotonically increased under light exposure. By contrast, they reached plateaus after 24 h in darkness, confirming the photodegradation of OTCs. A release kinetics model was established and correctly interpreted the microplastics size effect on the OTC release process. Finally, the impacts of salinity and dissolved organic matter (DOM) were investigated. The release and photodegradation of OTCs were both inhibited at high salinity conditions, probably due to the enhanced readsorption of OTCs on PVC microplastics and the formation of halogen radicals that were less reactive toward neutral OTCs. The presence of DOM, however, increased OTCs release probably because the excited state triplet DOM (3DOM*) formed and reacted with OTCs from PVC microplastics.

Transformation Products of Fluoxetine Formed by Photodegradation in Water and Biodegradation in Zebrafish Embryos ( Danio rerio).

The present study investigates the transformation of the antidepressant fluoxetine (FLX) by photo- and biodegradation and shows similarities and differences in transformation products (TPs). TPs were identified using LC-high-resolution mass spectrometry with positive and negative electrospray ionization. In a sunlight simulator, photodegradation was carried out using ultrapure water (pH 6, 8, and 10) and surface water (pH 8) to study the effect of direct and indirect photolysis, respectively. The well-known metabolite norfluoxetine (NFLX) proved to be a minor TP in photolysis (≤2% of degraded FLX). In addition, 26 TPs were detected, which were formed by cleavage of the phenolether bond ( O-dealkylation) which primarily formed 3-(methylamino)-1-phenyl-1-propanol (TP 166) and 4-(trifluoromethyl)phenol, by hydroxylation of the benzyl moiety, by CF3 substitution to benzoic aldehyde/acid, and by adduct formation at the amine group ( N-acylation with aldehydes and carboxylic acids). Higher pH favors the neutral species of FLX and the neutral/anionic species of primary TPs and, therefore, photodegradation. In zebrafish embryos, the bioconcentration factor of FLX was found to be 110, and about 1% of FLX taken up by the embryos was transformed to NFLX. Seven metabolites known from photodegradation and formed by hydrolysis, hydroxylation, and N-acylation as well as three new metabolites formed by N-hydroxylation, N-methylation, and attachment of an amine group were identified in zebrafish embryos. The study highlights the importance of considering a broad range of TPs of FLX in fresh water systems and in ecotoxicity tests and to include TP formation in both environmental processes and metabolism in organisms.

Changes in ecotoxicity of naphthalene and alkylated naphthalenes during photodegradation in water

Crude oil released into the environment contains many polycyclic aromatic hydrocarbons (PAHs). Alkylated PAHs are more abundant than unsubstituted PAHs and their toxicity is also of serious concern. Among the various physical, chemical, and biological weathering processes of crude oils, photodegradation is one of the most important for determining the environmental fate of oil residues. In this study, the photodegradation rate constants of naphthalene and alkylated naphthalenes were determined under simulated laboratory conditions at different temperature. Changes in the luminescence inhibition of Aliivibrio fischeri, as an indicator of the baseline toxicity, were observed in photodegradation mixtures. The major transformation products were also identified by gas chromatography–mass spectrometry. The photodegradation of naphthalene and the eight alkylated naphthalenes was described well by pseudo-first-order kinetics regardless of experimental temperature. The measured toxicity of the reaction mixtures obtained by photodegradative weathering slightly increased initially and then decreased with further weathering. In all cases, the observed toxicity was greater than accounted for by the parent compounds, indicating that the photodegradation products also contributed significantly to the overall toxicity of the mixtures. The identified photodegradation products were mostly oxygenated compounds such as alcohols, aldehydes, ketones, and quinones, which warrant further investigation.

Facile synthesis of zinc oxide crystal and insight into its morphological effect on organic dye photodegradation in water

Metal oxides particularly for zinc oxide (ZnO) particles are well-known to exhibit photocatalytic activities. However, the specific morphology and superstructure of nanomaterials can significantly influence this capacity. Here, it is shown that different crystalline structures of ZnO particles are provided by a facile one-step wet-chemical route. One possible formation mechanism has been elucidated for the fabrication of distinct metal oxide samples including flower-like, sphere-like and leaf-like ZnO under different synthesis conditions. It is also found that the photodegradative performance for organic dye is directly correlated to the morphological properties of these as-prepared catalysts; the higher the active surface area the better is the photocatalytic efficiency. Not only can ZnO structure with abundant mesoporous aggregated by leaf-shape arrays lead to more methylene blue immobilization, but also generate more photoinduced electrons and holes on the crystalline surface. The results also illustrate that the morphology-dependent catalytic performance can be further improved combining with other optimized photodegradative conditions (e.g. pH, illumination mode). The present study can lead to new metal oxide with high-performance important for photocatalytic and environmental applications.

Molecular iodine enhancing sulfadiazine photodegradation in water under UVA irradiation

Photodegradation of sulfadiazine (SD), a typical sulfonamide antibiotic (SA) frequently detected in the aquatic environment, under UVA irradiation enhanced by molecular iodine was investigated. Herein, molecular iodine I2 and coexisting I3− were provided by hydrogen peroxide and potassium iodide in acidic solution. During the treatment, highly reactive iodine radicals (I·, I2−), produced by UVA photolytic activation of both I2 and I3−, were verified as the dominated oxidant species against the decomposition of SD in aqueous solution. Besides, SD removal was found to be affected by the initial pH value, KI and H2O2 added concentrations.