Ternary semiconductor photocatalysts for the degradation of benzene-toluene-xylene in aqueous phase

Wastewater produced from the petroleum industry contains hazardous organic compounds such as benzene, toluene and xylene (BTX). A method based on advanced oxidation process has been applied to treat the organic compounds using semiconductor photocatalysts. Three types of ternary photocatalysts,namely ZnO/WO3/SnO2(ZWS), ZnO/WO3/Fe2O3(ZWF) andZnO/WO3/TiO2(ZWT) were prepared viamodified sol-gel method with different percentage ofatomic ratios of each metal oxide. Characterization of the catalyst was conducted using X-ray diffraction (XRD), diffuse reflectance ultra-violetspectroscopy (DR-UV), field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX) and nitrogen adsorptionanalyses. The XRD analysis revealed that all the prepared catalysts are mostlyin polycrystalline phases. The existence of binary species such as ZnWO4, SnW3O9 and Fe2WO6 were detected in the bulk matrices of the ternary oxide catalysts. The types of physisorption isotherm represented by ZWS (90:9:1), ZWS (90:3:7), ZWS (33:33:34) and ZWT (33:33:34) photocatalysts were of the Type IV isotherm and hysteresis loop assigned for the mesoporousity of the respective catalysts. The band gap energy of each photocatalyst was determined by DR-UV and it showedthat the band gap was affected by the change in ratio of the precursors. FESEM-EDX analysis for all the prepared ternary catalysts exhibited small and dispersed particles. The photocatalytic activity of the prepared ternary catalysts was tested on thesimulated BTX aqueous phase (1000 ppm)irradiated under UV-light. ZWSwith the ratio of 90:3:7, 7:3:90 and 1:90:9gave 66.97%, 59.02% and 61.01% of the BTX degradation, respectively. Meanwhile, ZWF (33:33:34), ZWS (33:33:34), and ZWT (33:33:34)photocatalysts gave43.27%,68.58%, and 70.41% of the BTX degradation, respectively. All the degradation processes were conducted using365 nm UV-light at ambient temperature and pressure. The total organic carbon (TOC) analysis revealed that the percentageof mineralization of the treated compounds were 40.58% (ZWF33:33:34), 64.91% (ZWS33:33:34), and 65.36% (ZWS33:33:34) with slightly increased in the percentage of degradation using 312 nm light source. The optimum concentration of H2O2used was 10 ppmwith72.32% of BTX degradation using ZWTphotocatalystand365 nm UV-light source. The reproducibility study usingZWTcatalyst immobilized on quartz glass showed that the photocatalyticactivity decreased gradually after the first usag

Preparation and characterization of zinc oxide and titanium oxide polyethersulfone hybrid film photocatalysts for degradation of methyl orange

Environmental issues and scarcity of water reserves have led to the development of photocatalyst technology to recycle the polluted water. The photocatalyst is usually applied in powder form but suffers several drawbacks; (i) agglomeration which led to a decrease in photoactivity and (ii) difficult and costly recovery process. These problems could be overcome by immobilizing the catalyst on a support. With the aim to provide alternative solution to the solid–liquid separation problem, polyethersulfone (PES) was chosen as the support due to its stability against radicals produced during photocatalytic reaction. This work investigated the physicochemical characteristics of TiO2/PES, ZnO/PES and reduced TiO2 (rTiO2)/PES hybrid film photocatalyst prepared via phase inversion technique and reported, for the first time, its synergistic contribution in the field of photocatalysis. The films were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and UV-vis Diffuse Reflectance Spectroscopy (UV-vis DRS) analyses. XRD, SEM and EDX analyses revealed that the TiO2, ZnO and reduced TiO2 (rTiO2) were homogeneously dispersed and embedded onto the PES film. XPS and UV-vis DRS results confirmed the existence of interstitial site of TiO2 (458.2 and 463.9 eV), ZnO (1021.0 and 1043.8 eV) and rTiO2 (456.1 and 461.8 eV) with their respective band gap energy of 3.00, 3.15 and 2.85 eV. The films exhibited higher surface roughness and enhance hydrophilicity compared to PES film alone. The photoactivity of the films was evaluated with respect to methyl orange (MO) degradation under both UV and visible light irradiation. Emphasis was placed on the effect of catalyst loading, pH, concentration, number of films and recyclability study. The best film photocatalysts displayed pseudo first-order kinetics with almost 80% and 30% for PES–TiO2 (13 wt%), 100% and 56% for PES– ZnO (17 wt%), 76% and 55% for PES–rTiO2 (13 wt%) of MO removal under original condition against UV and visible light irradiation, respectively. A complete removal of MO was achieved at pH 2.0 for both PES–TiO2 (13 wt%) and PES–rTiO2 (13 wt%) and pH 5.8 for PES–ZnO (17 wt%). The degradation percentage decreased with increasing initial concentration of MO (5–20 mg/L) but increased with increasing number of films. The major active species were found to be •O2 – for both PES–TiO2 (13 wt%) and PES– rTiO2 (13 wt%) and h+ for PES–ZnO (17 wt%). The best films can be recycled for up to five times while retaining its stability and degradation efficiency without being subjected to any regeneration process. The degradation of palm oil mill effluent (POME) was monitored through chemical oxygen demand (COD) analysis with degradation percentage of 20%, 27%, 12% and 12%, 18%, 15% under UV and visible light irradiation, respectively with some reduction in American Dye Manufacturers’ Institute (ADMI) colour values

Hybrid polymer-based photocatalytic materials for the removal of selected endocrine disrupting chemicals (EDCs) from aqueous media: a review

The progress of hybrid polymer-based photocatalytic materials has captivated massive interest from researchers to expand the works of this specially fabricated material, exclusively for removing hazardous endocrine-disrupting chemicals (EDCs) in aqueous media. Several attractive features such as enormous pore structures, tunable band gap energy, excellent mechanical, chemical, and thermal properties with outstanding photoactivity and recyclability offer a new vision against traditional photocatalysts, which are ordinarily used in suspension mode. A deterioration in the freshwater reservoir is bearing notable domestic and industrial challenges. Nonetheless, their efficacy for the photo-removal of EDCs can be boosted by conducting surface or bulk modifications utilizing appropriate inorganic fillers for better interaction within the selected polymer matrix. This review discussed the performances of several hybrid polymer-based photocatalytic materials to eliminate distinct classes of EDCs and the implicated mechanism. The introduction of hybrid polymer-based photocatalytic materials in the water recovery process implies that developing the innovative protocol is obligatory for effectively removing EDCs from the ecosystem

Metal-organic frameworks (MOFs) for the adsorptive removal of selected endocrine disrupting compounds (EDCs) from aqueous solution: A review

The progress of water-stable metal-organic frameworks (MOFs) has drawn interest from scientists to expand the research on this unique porous material, especially for the elimination of endocrine disrupting compounds (EDCs) from aqueous solutions via adsorption. Several controlling variables such as tunable porosity, hierarchical structure, immense pore volume and surface area, excellent adsorption and recyclability performances offer a new insight when compared with traditional adsorbents. The instability and toxicity of MOFs in water are a huge challenge in practical applications. Nevertheless, their capability and selectivity for the removal of EDCs can be justified by employing suitable metal ion clusters, organic linkers, and surface/bulk modifications. This review discusses the performance of several MOFs for the extermination of diverse categories of EDCs and the plausible adsorption mechanism involved. The importance of MOFs in environmental applications signifies that the development of advanced technology is required for the successful removal of EDCs from the aqueous environment

Photoactive Hybrid Film Photocatalyst of Polyethersulfone-ZnO for the Degradation of Methyl Orange Dye: Kinetic Study and Operational Parameters

A facile and effective technique to immobilize photocatalyst nanoparticles by incorporating zinc oxide (ZnO) into polyethersulfone polymeric films by means of a phase inversion technique is reported. The degradation study of methyl orange (MO) dye was performed using a series of ZnO-embedded polymer hybrid systems. The photoactivity of the films increased in parallel with increased ZnO loading up to 17 wt%. The photodegradation process followed a pseudo first-order kinetics with an achievement of almost 100% MO removal in original conditions. The PZ-17 film demonstrated an excellent and comparable degradation performance up to five cycles, signifying the reliability of the film photocatalyst against ultraviolet irradiation and degradation

Visible light-active hybrid film photocatalyst of polyethersulfone–reduced TiO2: photocatalytic response and radical trapping investigation

The present work emphasizes the facile synthesis and characterization of reduced TiO2–polyethersulfone and evaluation of its visible light photocatalytic response. Reduced TiO2 (rTiO2) was prepared by a simple thermal reduction of NaBH4 at 300 °C for 50 min before immobilized into polyethersulfone polymer film via phase inversion. X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray characterization showed the photoactive rTiO2 was still intact onto the PES with homogeneous dispersion after the preparation process. The incorporation of rTiO2 was observed to improve the hydrophilicity and film’s surface roughness up to 7.03 nm. X-ray photoelectron spectroscopy confirmed the formation of interstitial site of rTiO2 at lower binding energies of 456.1 and 461.8 eV, which extends visible light absorption by either the existence of Ti3+ species or oxygen vacancies. The low band gap (2.85 eV) of the film photocatalyst synergistically envisages the best degradation performance at 13 wt% of rTiO2 loading by degrading 100% methyl orange in acidic conditions. Based on pseudo-first-order kinetic model, the highest degradation rate constant of 1.41 × 10−3 min−1 was obtained with ·O2− acted as the main active species during the process. The reusability studies revealed that the film photocatalyst could be repeatedly used for up to five times without severe deactivation

Photoactive Hybrid Film Photocatalyst of Polyethersulfone-ZnO for the Degradation of Methyl Orange Dye: Kinetic Study and Operational Parameters

A facile and effective technique to immobilize photocatalyst nanoparticles by incorporating zinc oxide (ZnO) into polyethersulfone polymeric films by means of a phase inversion technique is reported. The degradation study of methyl orange (MO) dye was performed using a series of ZnO-embedded polymer hybrid systems. The photoactivity of the films increased in parallel with increased ZnO loading up to 17 wt%. The photodegradation process followed a pseudo first-order kinetics with an achievement of almost 100% MO removal in original conditions. The PZ-17 film demonstrated an excellent and comparable degradation performance up to five cycles, signifying the reliability of the film photocatalyst against ultraviolet irradiation and degradation

Pb(II) removal in water via adsorption onto deep eutectic solvent fabricated activated carbon

In our current work, we have established a novel approach in the synthesis of a new adsorbent by using choline chloride and urea (DES)/orthophosphoric acid (H3PO4) as our activating agent and palm kernel shell (PKS) as our precursor. The resulting activated carbon (DES/H3PO4-6002:3) was used to adsorb Pb(II) from aqueous solution. Characterization of DES-H3PO4-6002:3 by nitrogen adsorption/desorption isotherm measurements, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) demonstrated good micropores structure and high surface area that makes DES/H3PO4-600 2:3 a suitable alternative for liquid phase adsorption. The fundamental batch experiment of DES/H3PO4-600 2:3 was investigated by different parameters (such as concentration, pH, temperature and absorbent dose). The results obtained indicated that Langmuir model and pseudo-second-order equation best fit the data, indicating that the adsorption was controlled by chemical reaction and monolayer uptake. In addition, the fabrication of DES/H3PO4 AC exhibits good potential for Pb(II) ions uptake, including its high adsorption capacity (97.1 mg/g) and good recyclability. The future potential of this works lies in the identification of alternatives to environmental benign synthesis AC and reuse of Pb(II) ion–laden biosorbent after heavy metal uptake

Efficient photodegradation of paracetamol by integrated PES-ZnO photocatalyst sheets

In this study, PES-ZnO (Polyethersulphone-Zinc Oxide PZ) photocatalyst sheets were prepared via the phase inversion method and used in the oxidative degradation of paracetamol, a commonly detected pharmaceutical in water matrices. The incorporation of ZnO in the polymer matrix, confirmed by X-ray Diffraction (XRD), Scanning Electron Microscope/Energy Dispersive X-ray (SEM-EDX), and X-ray Photoelectron Spectroscopy (XPS) analyses, led to formation of porous structure with tear-like pores that subsequently increased the porosity of the polymer matrix PZ sheet. The PZ sheet containing 15 wt of ZnO, PZ-15, exhibited 92 degradation efficiency at a slightly alkaline condition when using four pieces of the PZ-15 sheet. The degradation rate constant of 4.8 — 10-3 minˆ’ 1 , based on pseudo-first-order kinetics, was obtained with hydroxyl radicals identified as the main species responsible for the degradation of paracetamol. The degradation process proceeded via hydroxyl radical attack of the C““C at the para position of the compound that yields hydroquinone as a by-product. The reusability study demonstrated the feasibility and reliability of using the PZ-15 photocatalyst sheet for up to six cycles with comparable performance in the degradation of paracetamol in an aqueous solution

Fabrication of Ag3PO4 /g-C3N4 composite: enhanced charge separation and outstanding photoactivity under very low intensity visible light irradiation

A visible light driven Ag3PO4/g-C3N4 composite photocatalyst was synthesized by a simple coprecipitaion method by changing the loadings of g-C3N4 for degradation of methyl orange (MO) dye under very low visible light intensity. The results revealed that the introduction of g-C3N4 onto Ag3PO4 surface greatly improved its stability and photocatalitic activity. It was found that Ag3PO4/g-C3N4 with mass ratio Ag3PO4:g-C3N4 of 1:0.03 exhibited 98% of degradation under 20 minutes of irradiation time. The study proved that h+ played the chief role in the degradation process and a possible heterojunction mechanism was proposed