Activation of peroxymonosulfate by BiOCl@Fe3O4 catalyst for the degradation of atenolol: Kinetics, parameters, products and mechanism.

BiOCl@Fe3O4 photocatalyst was synthesized to activate peroxymonosulfate (PMS) for atenolol (ATL) degradation under simulated sunlight irradiation in present study. XRD, SEM, adsorbability and pore size distribution of BiOCl@Fe3O4 were analyzed. Magnetic BiOCl performed high activity in PMS activation and could be easily solid-liquid separation by applying an external magnetic field. Many parameters were inspected, including scavengers, PMS concentration, catalyst dosage, pH, anions (Cl- and CO3-). h+, SO4-, HO, O2-, SO5- were involved in ATL degradation in BiOCl@Fe3O4/PMS/sunlight system. The second-order rate constant of the reaction between ATL and SO4- (kATL, SO4-) was estimated via laser flash photolysis experiments. Moreover, ATL mineralization was followed by TOC analyzer. Twelve possible intermediate products were identified through LC-QTOF-MS analysis, and six ATL degradation pathways were concluded. This type of magnetic photocatalyst is characterized by ease of separation, high activation and good reusability. It may have application potential in refractory organic pollutants degradation.

Degradation of atenolol via heterogeneous activation of persulfate by using BiOCl@Fe3O4 catalyst under simulated solar light irradiation.

Efficient oxidative degradation of pharmaceutical pollutants in aquatic environments is of great importance. This study used magnetic BiOCl@Fe3O4 catalyst to activate persulfate (PS) under simulated solar light irradiation. This degradation system was evaluated using atenolol (ATL) as target pollutant. Four reactive species were identified in the sunlight/BiOCl@Fe3O4/PS system. The decreasing order of the contribution of each reactive species on ATL degradation was as follows: h+ ≈ HO· > O2·- > SO4·-. pH significantly influenced ATL degradation, and an acidic condition favored the reaction. High degradation efficiencies were obtained at pH 2.3-5.5. ATL degradation rate increased with increased catalyst and PS contents. Moreover, ATL mineralization was higher in the sunlight/BiOCl@Fe3O4/PS system than in the sunlight/BiOCl@Fe3O4 or sunlight/PS system. Nine possible intermediate products were identified through LC-MS analysis, and a degradation pathway for ATL was proposed. The BiOCl@Fe3O4 nanomagnetic composite catalyst was synthesized in this work. This catalyst was easily separated and recovered from a treated solution by using a magnet, and it demonstrated a high catalytic activity. Increased amount of the BiOCl@Fe3O4 catalyst obviously accelerated the efficiency of ATL degradation, and the reusability of the catalyst allowed the addition of a large dosage of BiOCl@Fe3O4 to improve the degradation efficiency.

Photodegradation of carbamazepine with BiOCl/Fe3O4 catalyst under simulated solar light irradiation.

A magnetic BiOCl/Fe3O4 catalyst with simulated solar light response was successfully prepared through a precipitation process and characterized by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance spectroscopy, VSM, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy. The photocatalytic activity of BiOCl/Fe3O4 nanocomposites was further investigated through the photodegradation efficiency of carbamazepine (CBZ). In this study, 90.3% of CBZ was removed after 60min irradiation in the presence of the BiOCl/Fe3O4 catalyst. Three reactive species were identified; the contribution of h+, HO, and O2- to CBZ degradation was approximately 94.98%, 3.25%, and 1.06%, respectively. The pH value had a significant effect on the CBZ degradation, and the best performance was achieved at pH 2.68. The presence of common anions (NO3-, Cl-, CO32-, and SO42-) also affected the CBZ degradation. The inhibiting effect followed the order of CO32->SO42->Cl-. However, NO3- weakly favored the photodegradation of CBZ. Moreover, the BiOCl/Fe3O4 photocatalyst could be easily recollected from the solution by applying an external magnetic field. This type of magnetic photocatalyst, which is characterized by ease of separation, may have application potential in wastewater treatment. The disappearance of CBZ as well as the formation of its products were determined by liquid chromatography mass spectroscopy and the possible photocatalytic degradation pathways were proposed.

Preparation and formation mechanism of BiOCl0.75I0.25 nanospheres by precipitation method in alcohol-water mixed solvents.

BiOCl0.75I0.25 crystals with irregular three-dimensional (3D) flower-like and hierarchical nanosphere-like structures were successfully synthesized in different alcohol-water mixed solvents by precipitation method. The primary formation mechanism of BiOCl0.75I0.25 nanospheres was investigated by taking water, monohydric alcohols (ethanol and isopropanol), and polyhydric alcohols (ethylene glycol, diethylene glycol, and glycerol) as solvents in the synthesis process. The obtained BiOCl0.75I0.25 samples were characterized by powder X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and nitrogen adsorption. Results showed that the alcohol solvents with different physical and chemical properties used in the synthesis process performed significant functions in directing the morphology and surface pore structure of BiOCl0.75I0.25 crystals. Meanwhile, BiOCl0.75I0.25 synthesized in various solvents exhibited morphology-dependent adsorption and photocatalytic degradation abilities in removing p-hydroxyphenylacetic acid (p-HPA), which was used as a model pollutant, in aqueous solutions under simulated solar light (λ⩾290nm). In addition, the fabrication process of the crystal products was proposed through a series of time-dependent experiments.

Aqueous photodegradation of 4-tert-butylphenol: By-products, degradation pathway and theoretical calculation assessment.

4-tert-butylphenol (4-t-BP), an endocrine disrupting chemical, is widely distributed in natural bodies of water but is difficult to biodegrade. In this study, we focused on the transformation of 4-t-BP in photo-initiated degradation processes. The steady-state photolysis and laser flash photolysis (LFP) experiments were conducted in order to elucidate its degradation mechanism. Identification of products was performed using the GC-MS, LC-MS and theoretical calculation techniques. The oxidation pathway of 4-t-BP by hydroxyl radical (HO) was also studied and H2O2 was added to produce HO. 4-tert-butylcatechol and 4-tert-butylphenol dimer were produced in 4-t-BP direct photolysis. 4-tert-butylcatechol and hydroquinone were produced by the oxidation of HO. But the formation mechanism of 4-tert-butylcatechol in the two processes was different. The benzene ring was fractured in 4-t-BP oxidation process and 29% of TOC was degraded after 16h irradiation.

Photodegradation of 4-tert-butylphenol in aqueous solution by UV-C, UV/H2O2 and UV/S2O8(2-) system.

The photolytic degradation of 4-tert-butylphenol (4-t-BP) in aqueous solution was investigated using three kinds of systems: UV-C directly photodegradation system, UV/H2O2 and UV/S2O8(2-) system. Under experimental conditions, the degradation rate of 4-t-BP was in the order: UV/S2O8(2-) > UV/H2O2 > UV-C. The reaction kinetics of UV/S2O8(2-) system were thoroughly investigated. The increase of S2O8(2-) concentration enhanced the 4-t-BP degradation rate, which was inhibited when the concentration of S2O8(2-) exceeded 4.0 mM. The highest efficacy in 4-t-BP degradation was obtained at pH 6.5. The oxidation rate of 4-t-BP could be accelerated by increasing the reaction temperature and irradiation intensity. The highest rate constant (kobs = 8.4 × 10(-2) min(-1)) was acquired when the reaction temperature was 45 °C. The irradiation intensity was measured by irradiation distance, and the optimum irradiation distance was 10 cm. Moreover, the preliminary mechanism of 4-t-BP degradation was studied. The bond scission of the 4-t-BP molecule occurred by the oxidation of SO4(•-), which dimerized and formed two main primary products. Under the conditions of room temperature (25 °C ± 1 °C) and low concentration of K2S2O8 (0.5 mM), 35.4% of total organic carbon (TOC) was removed after 8.5-h irradiation. The results showed that UV/S2O8(2-) system was effective for the degradation of 4-t-BP.