Enhanced visible light photodegradation of pharmaceutical pollutant, warfarin by nano-sized SnTe, effect of supporting, catalyst dose, and scavengers

A core/shell TiO2 magnetized molecularly imprinted photocatalyst (MMIP@TiO2): synthesis and its photodegradation activity towards sulfasalazine

Although the selectivity of TiO₂ for the degradation of target molecules is not enough, it is a broadly employed photocatalyst for the degradation of many pollutants. Molecularly imprinted compounds owing to their extreme recognition specificity have become increasingly popular for preparing selective photocatalysts. In this work, based on molecularly imprinted magnetized TiO₂ (MMIP@TiO₂), a selective photocatalyst was prepared. Via the co-precipitation method, Fe₃O₄ particles were prepared and coated respectively by SiO₂, vinyl end groups, and molecularly imprinted polymers (MIP). The synthesized photocatalyst was characterized by the X-ray diffraction method (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectrometry (EDX), vibrating sample magnetometry (VSM), high-performance liquid chromatography (HPLC), and photoluminescence analysis (PL). The photocatalyst was then used to degrade the sulfasalazine pharmaceutical pollutant under UV irradiation. An average crystallite size of 9 nm was obtained for the MMIP@TiO₂ sample from the Scherrer formula and 34.5 nm by the Williamson-Hall formula. The results revealed that compared to the non-imprinted counterpart, the molecularly imprinted photocatalyst had significantly higher efficiency and selectivity for the degradation of target molecules. The process was forwarded with 90% efficiency within 10 min. Optimal conditions were 10.0 min irradiation when 25 mL SSZ solution (50 mg/L), 0.07 g/L catalyst dose, and pH 6.0 were applied. The maximum removal efficiency was calculated to be 92%. The external magnetic field quickly removed the photocatalyst from the solution and regenerated it. It was revealed that after each regeneration cycle, the efficiency dropped. Nevertheless, 63% of the preliminary effectiveness remained after four regeneration steps.

Research Progress on Graphitic Carbon Nitride/Metal Oxide Composites: Synthesis and Photocatalytic Applications

Although graphitic carbon nitride (g-C3N4) has been reported for several decades, it is still an active material at the present time owing to its amazing properties exhibited in many applications, including photocatalysis. With the rapid development of characterization techniques, in-depth exploration has been conducted to reveal and utilize the natural properties of g-C3N4 through modifications. Among these, the assembly of g-C3N4 with metal oxides is an effective strategy which can not only improve electron-hole separation efficiency by forming a polymer-inorganic heterojunction, but also compensate for the redox capabilities of g-C3N4 owing to the varied oxidation states of metal ions, enhancing its photocatalytic performance. Herein, we summarized the research progress on the synthesis of g-C3N4 and its coupling with single- or multiple-metal oxides, and its photocatalytic applications in energy production and environmental protection, including the splitting of water to hydrogen, the reduction of CO2 to valuable fuels, the degradation of organic pollutants and the disinfection of bacteria. At the end, challenges and prospects in the synthesis and photocatalytic application of g-C3N4-based composites are proposed and an outlook is given.

Photocatalytic activity of new nanostructures of an Ag(i) metal–organic framework (Ag-MOF) for the efficient degradation of MCPA and 2,4-D herbicides under sunlight irradiation

A new Ag(i) metal–organic framework (Ag-MOF) [Ag(p-OH-C₆H₄COOH)₂(NO₃)]_n [Ag(PHBA)₂(NO₃)]_n, (1) (PHBA: C₈H₆O₄ {p-hydroxybenzoic acid}) was synthesized using two different methods; the laying method (single crystal) and sonochemical irradiation (nanostructures).

Eggshell recycling for fabrication of Pd@CaO, characterization and high-performance solar photocatalytic activity

Recycling of waste materials into useful products is a promising strategy for environmental protection. Eggshell is one of the globally produced huge wastes. In this work, calcium oxide (CaO) nanoparticles were recycled via calcination of chicken eggshells at 1100 °C for 2 h. A novel nanocomposite, made of loading palladium nanoparticles on calcium oxide surface (Pd@CaO), is successfully fabricated through solid-solid interaction. The materials were characterized using different physicochemical techniques: Fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-Vis), photoluminescence (PL) analysis, ultra-high resolution field emission scanning electron microscope (FE-SEM), transmittance electron microscope (TEM), and X-ray diffraction (XRD). The study sheds light on the ability of the materials to be used for detoxification of crystal violet dye as pollutant model under solar irradiation. The effects of operational conditions, such as catalyst mass, initial dye concentration, pH, and illumination time, have been tested. The optimum conditions for crystal violet photocatalytic degradation in the presence of Pd@CaO were mild conditions. Control experiments studied the effect of sunlight in the absence of the catalyst, and the effect of the catalyst in the absence of sunlight does not provide the significant removal exhibited in the presence of catalyst under solar irradiation.

Photodegradation of ibuprofen and four other pharmaceutical pollutants on natural pigments sensitized TiO2 nanoparticles

Pharmaceuticals and personal care products (PPCPs) in water system have drawn increasing concerns in recent years. TiO₂ -based photodegradation has shown great potential as a low-cost and sustainable technology in water treatment, however, can only use the UV light range of solar radiation which makes the system less efficient. Dyes have been studied to improve the TiO₂ system light-harvesting range, but studies on environmental friendly natural dyes are rare. In this study, a screening method using UV-Vis spectra analysis was carried out on a group of 22 different tropical natural plants for the potential applications on dye-sensitized TiO₂ in PPCP treatment. As a result, Begonia "Martin's Mystery" significantly increased TiO₂ photodegradation efficiency toward ibuprofen treatments which is first time reported in literature as our best knowledge. Moreover, the promising discovery of Begonia application in ibuprofen treatment has been successfully applied to warfarin and famotidine treatment. Similar results were expanded to many other Begonia species which indicate that Begonia extracts could be excellent sensitizers for TiO₂ -based photodegradation of PPCPs. Our discovery suggested that the screening process may potentially open a brand-new way for future TiO₂ photodegradation studies before the complex and time-consuming detailed mechanism studies. PRACTITIONER POINTS.: Natural dyes were screened as sensitizers for TiO₂ photodegradation of ibuprofen. Ibuprofen photodegradation efficiency was increased twice using Begonia "Martin's Mystery." The Begonia applications were extended to warfarin, trimethoprim, and famotidine. Promising results were also observed using five other Begonia species.

Recent advances of SBA-15-based composites as the heterogeneous catalysts in water decontamination: A mini-review

As an emerging class of silica-based mesoporous materials with incorporation of active components (e.g., transition metals/metal oxides and nanocarbons), SBA-15-based composites (X@SBA-15) have been attracting increasing attention in the field of water treatment owing to their unique characteristics and excellent remediation performance. This paper reviews recent advances in catalytic applications of X@SBA-15 to remove organic contaminants from water. Emphasis is made on the use of X@SBA-15 in four advanced oxidation processes (AOPs) (i.e., photocatalysis, Fenton-like oxidation, catalytic ozonation, and sulfate radical-based oxidation). Impregnation and hydrothermal methods are two most widely used synthetic approaches to combine the active composites with SBA-15, obtaining a synergistic effect with significant improvement in their individual catalytic activity for pollution remediation. The enhanced generation of highly reactive hydroxyl radicals from the surface of X@SBA-15 was widely recognized as being responsible for water decontamination using these AOPs, while sulfate radicals were also involved during activation of persulfate or peroxymonosulfate. Especially, X@SBA-15 could significantly enhance the light harvest and reduce the recombination of photo-induced electrons and holes during photocatalytic treatment, which also played the critical role in oxidizing the organics. The superior catalytic performance of X@SBA-15 without leaching metal ions during successive runs demonstrated the excellent reusability and structural stability. Together with the reduced toxicity of the treated solutions and the cost-effective characteristics of X@SBA-15 nanohybrids reported in the published literature, their great potential as the efficient and environmentally friendly heterogeneous catalysts in a real use scenario is suggested. Finally, the future perspectives on the development and practical utilization of X@SBA-15 are addressed.

Elimination of highly consumed herbicide; 2,4-dichlorophenoxyacetic acid from aqueous solution by TiO2 impregnated clinoptilolite, study of degradation pathway

In this research, the degradation of the highly consumed herbicide, 2,4-dichlorophenoxy acetic acid, was evaluated by a nanophotocatalyst prepared by impregnation of natural zeolite clinoptilolite with TiO₂. The photodegradation process of was studied under UV and visible light irradiations. To optimize the influencing parameters on the degradation efficiency, the Design Expert software and the Response surface methodology were used. The predicted values obtained by the methods were in good agreement with the experimental data. The degradation efficiency determined by UV-Vis spectroscopy indicated that the optimized degradation efficiency (58% by UV, and 31% by visible light) was obtained at pH = 6, catalyst dose of 0.4 g L^-1, pollutant concentration of 6 mg L^-1, and irradiation time of 95 min. The reaction mechanism was studied by Gaussian 03 program and a computer simulation method (density functional theory). The results were in good agreement with the results of the HPLC method used for identification of the degradation products. The mineralization of the pollutant was evaluated by measurement of total organic carbon of the degradation solution before and after irradiations. The results indicated that the degraded pollutant was mostly mineralized and converted to of CO₂ and H₂O.