The occurrence of benzophenone-3 (BP-3) in aquatic environments constitutes a potential risk to the environment and human health due to its phytotoxicity, carcinogenicity and endocrine disrupting effects. In this work, cobalt ferrite (CoFe O ) prepared by chemical co-precipitation method was used as a catalyst for the degradation of BP-3. The catalyst was characterized by SEM, TEM, XRD, XPS, BET and FT-IR spectroscopy, and its catalytic activity on BP-3 removal by persulfate (PS) was then evaluated at different operating parameters (catalyst loading, reaction temperature, solution pH and PS dose). The removal of BP-3 (1.31 μM) in 6 h reached 91% under the condition of [BP-3] : [PS] = 1: 1000, initial pH = 7.0, T = 25 °C and catalyst load = 500 mg L . In addition to the satisfactory catalytic performance, the CoFe O also showed high stability and excellent recyclability. Electron paramagnetic resonance and radical quenching tests showed that sulfate radicals predominated in the decomposition of BP-3 by PS/CoFe O , while hydroxyl radicals also contributed to the catalytic oxidation process. Fifteen degradation products were identified by liquid chromatography-mass spectrometry (LC-MS), and two reaction pathways involving hydroxylation, demethylation, direct oxidation and benzene ring opening were proposed. This study could provide useful information for the potential application of CoFe O activated PS technology to treat water and wastewaters containing BP-3.
By using CNTs functionalized by oxygenic functional groups ( COOH or OH) as the carbon source, novel catalysts of nitrogen (N) and sulfur (S) co-doped multi-walled carbon nanotubes (CNTs) were prepared for the first time by thermal decomposition. The obtained CNTs were characterized by SEM, TEM, BET, XPS, XRD, FT-IR and Raman spectroscopy. Additionally, the new material was used as a catalyst for the activation of peroxymonosulfate (PMS) for the degradation of benzophenone-4 (BP-4). Results indicated that the COOH group plays an important role in the S doping process. Moreover, binary (N and S)-doped CNT-COOH (NS-CNT-COOH) exhibited a notably enhanced catalytic activity towards PMS for degrading BP-4. This activity level was approximately five-fold greater than that of singly (N)-doped CNT-COOH and binary (N and S)-doped CNT, and it even exceeded that of the metal catalyst CuFe O . The enhanced catalytic performance was attributed to the active sites generated by the introduced pyridinic and pyrrolic N atoms and thiophenic S atoms. The effects of various factors on the catalytic activity of NS-CNT-COOH were studied. Results revealed that the degradation efficiency of BP-4 increased with catalyst load, oxidant concentration and reaction temperature. In contrast, NS-CNT-COOH exhibited no remarkable catalytic activity towards peroxodisulfate (PDS) and H O . In the case of the NS-CNT-COOH/PMS system, a possible pathway for BP-4 degradation was proposed and based on detected intermediates. The mechanism was justified by theoretical calculations of the frontier electron densities, which have not been reported previously. Furthermore, mineralization, toxicity, stability and reusability tests suggested that the developed catalyst, NS-CNT-COOH, holds promise for practical application.
Instead of previously reported graphene oxide (GO), industrial graphene (reduced graphene oxide (IrGO)) was annealed with a nitrogen precursor. The obtained nitrogen-doped graphene (N-IrGO) was then employed as a novel catalyst for peroxymonosulfate (PMS) activation to degrade benzophenone-1 (BP-1) for the first time. The results show that N-IrGO exhibits excellent catalytic performance over conventional GO and its nitrogen-doped sample and was even better than the metal catalysts Co O and Fe O . The enhanced catalytic performance might be attributed to graphitic-like nitrogen. Moreover, the effects of various factors were studied, including catalyst load, PMS concentration and reaction temperature. Possible degradation pathways of BP-1 in the N-IrGO/PMS system were proposed based on detected intermediates and the frontier electron density calculation. Radical quenching experiments and electron paramagnetic resonance (EPR) tests indicated that nonradical oxidation (singlet oxygen ( O )) plays a dominant role in the BP-1 degradation, in contrast to the previously proposed radical process. Finally, mineralization and stability experiments confirmed that N-IrGO may be an alternative catalyst for environmental remediation. This study contributes to designing novel graphene materials with N doping and gives new insight into nonradical oxidation on benzophenone-type UV filters degradation.
Benzophenone-3 (BP-3) is a widely used organic UV filter in sunscreen which has been detected in surface and groundwater. BP-3 can affect the aquatic environment and human health. In this study, PbO/TiO and Sb O /TiO photocatalyst were synthesized for the photocatalytic degradation of Benzophenone-3 (BP-3) and various degradation parameters such as initial pH value, initial concentration, and the dose of catalysts were optimized. Two different TiO based catalysts PbO/TiO and Sb O /TiO were synthesized by hydrothermal method. Synthesized photocatalysts were characterized by X-ray diffraction pattern (XRD), scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), BET and UV–Vis DRS techniques. Molar ratio variation of PbO and Sb O with respect to TiO significantly affected the surface area, structure, and bandgap of photocatalyst and hence the variation in degradation efficiency of the photocatalyst was observed. The BP-3 can be completely degraded by using PbO/TiO within 120 min under UV-C irradiation. The highest degradation of BP-3 was obtained for the 20 µM concentration at pH 7 when the dose was adjusted to be 0.75 g/L. However, negligible degradation of BP-3 was demonstrated in the absence of a catalyst. Moreover, with the catalysts PbO/TiO and Sb O /TiO , BP-3 followed the pseudo-first-order kinetics with a rate constant of 3.58 × 10 min and 0.92 × 10 min respectively. Electron paramagnetic resonance (EPR) spectrum with three distinct peaks with an intensity of 1:1:1 showed the presence of TEMP- O adduct which suggested the generation of O (singlet oxygen) in both catalysts. The plausible mechanism of BP-3 degradation was proposed by the Gas chromatography-mass spectrometry (GC-MS) analysis which showed the formation of pentamethyl- and 5-Hydroxy-7-methoxy-2-methyl-3-phenyl-4-chromenone byproducts on BP-3 photocatalytic degradation by the synthesized catalyst.
Three new silylated 2-(2'-hydroxyphenyl)benzotriazole derivatives were prepared. Starting with the easily available simple 2-(2'-hydroxyphenyl)benzotriazole, the target compounds were synthesized by a stepwise synthetic protocol, namely alkylation, thermal rearrangement and silylation.
A laboratory-scale combined UV photodegradation and biotrickling filter (UV–BTF) system as well as a single biotrickling filter (BTF) were evaluated for removal of gaseous styrene. Empty bed residence time (EBRT) and inlet styrene concentrations were 30–70 s and 0.5–4.0 g m . A maximum elimination capacity (EC ) of 309 g m h was achieved by the combined UV–BTF at an inlet loading rate (ILR) of 476 g m h with a removal efficiency (RE) of 65%. The better performance of BTF was due to the UV photodegradation that converted styrene into compounds that were more easily degraded (benzoate, phenol, isopropyl alcohol, etc.) for subsequent biological treatment. Bacterial community analysis revealed that abundant bacteria including (α-, β-, γ- and δ-), and were responsible for styrene removal in the BTF and UV–BTF. When subjected to short (12 h) and long-term (180 h) shut-downs, the combined system still offered high EC values of 156 and 304 g m h , respectively, after resuming operation at 2 and 12 h, respectively. Intermittent shutdown (3 d) with nutrient addition and a 10 d shutdown without nutrient addition had no apparent effects on the combined biofilter. The results showed that the UV photodegradation had a positive effect on the subsequent BTF, and the combined system was stable under both steady and transient states.
Benzophenone-3 (BP-3), an organic ultraviolet (UV) filter, is reported to exhibit endocrine disruptive effects. In this study, the degradation of BP-3 by UV/H O in aqueous solution was investigated by steady-state photolysis and laser flash photolysis experiments. The photolysis of BP-3 was not observed obviously after 8 h under UV irradiation ( = 254 nm), but the degradation of BP-3 could be conducted via UV/H O due to the oxidation by hydroxyl radical (HO ). At higher initial concentrations of BP-3, the degradation percentages decreased, and the optimal pH for the degradation of BP-3 was 6.0. The reaction of BP-3 and HO adhered to the pseudo-first-order kinetics. When the BP-3 concentration was 0.01 mM, the rate constants of the apparent first-order reaction and second-order reaction between BP-3 and HO were 1.26 × 10 s and 2.97 × 10 M s , respectively. Several intermediate products were obtained and the primary reaction pathway of BP-3 and HO was proposed.
Benzophenone-4 (BP4) is UV-filter that is widely in sunscreens and cosmetics to prevent skin damage from sunlight exposure. Washing off of BP4 from the human body in swimming pools represents a direct source of BP4 in the environment. In this study, we investigated the transformation of BP4 by free chlorine, chloramine, and UV/chlorine, which can be found in swimming pool water. It was found that BP4 can be rapidly removed by both chlorine and chloramine treatment, but only chlorination led to appreciable formation of chlorinated disinfection by-products (DBPs), such as dichloroacetic acid and trichloroacetic acid. However, chloramination of BP4 resulted in higher levels of chlorinated intermediates, which were relatively recalcitrant to further chlorination. The UV/chlorine process was significantly more efficient than the chlorine treatment alone for BP4 removal and resulted in trace chlorinated intermediates and formation of DBPs. Radical scavenger tests revealed that the removal of BP4 in the UV/chlorine process was mostly ascribed to reactions with the Cl and OH generated from HClO photolysis. The presence of methanol as a radical scavenger resulted in incomplete removal of BP4 in the UV/chlorine process and enhanced the formation of DBPs. The increase in DBP formation was because the residual BP4 can be exited to a triplet state ( BP4 ) upon UV irradiation. BP4 subsequently reacted with O to form O , a reactive oxygen species that generated DBPs by reacting with chlorinated intermediates in water. All benzophenone-type UV-filters may have similar photochemical activity and thus influence the transformation of other organics in sunlit surface water environments.
Magnetic spinel cobalt ferrite nanoparticles with variable composition (Co Fe O ; x = 0.1, 0.5, 0.7 and 1.0) were synthesized. The nanoparticles were characterized by various surface techniques. Average sizes and surface areas of ferrites were determined in the ranges of 11–34 nm and 18.5–49.1 m /g, respectively. Surface analysis of the nanoparticles confirmed the spinel type structures in which Co(II) incorporated into the crystal lattice. The synthesized catalysts were used to dissociate peroxomonosulphate (PMS) into reactive sulfate radicals ( ) and further into hydroxyl radicals ( ) to degrade a target pollutant, 2-phenylbenzimidazole-5-sulfonic acid (PBSA) in absence of heat and light. As the molar ratio of cobalt (i.e., x) in the ferrite catalyst increased from 0.1 to 1.0, PBSA degradation enhanced from 24 to 75% in 240 min. The removal of PBSA increased significantly with the increase in PMS concentration up to 0.1 mM, followed by a decrease at PMS levels of >0.1 mM. Nitrogen content in PBSA was mineralized by the cobalt ferrite-PMS system mostly into NO and NH ions with minor formation of NO . Only 32% TOC removal was observed over a 240 min reaction time, indicating carbon content in PBSA was not completely mineralized. A chemical probe method, based on free radical scavenging, revealed the contribution of both and species in PBSA degradation. Fifteen reaction intermediates were identified using LC/Q-TOF-ESI–MS analysis. Hydroxylation, elimination of sulfonate moiety, and ring cleavage processes were involved in the major degradation pathways. Catalyst reuse experiments demonstrated PBSA degradation efficiency either retained or increased with each subsequent reuse. The magnetic spinel Co-ferrite nanoparticles can be applied effectively to activate PMS without energy aiding for degrading harmful emerging organic contaminants in water.