Silver halide-based composite photocatalysts: an updated account

Graphene oxide-incorporated silver-based photocatalysts for enhanced degradation of organic toxins: a review

Environmental contamination and scarcity of energy have been deepening over the last few decades. Heterogeneous photocatalysis plays a prominent role in environmental remediation. The failure of earlier metal oxide systems like pure TiO₂ and ZnO as stable visible-light photocatalysts demanded more stable catalysts with high photodegradation efficiency. Silver-based semiconductor materials gained popularity as visible-light-responsive photocatalysts with a narrow bandgap. But their large-scale usage in natural water bodies for organic contaminant removal is minimal. The factors like self-photocorrosion and their slight solubility in water have prevented the commercial use. Various efforts have been made to improve their photocatalytic activity. This review focuses on those studies in which silver-based semiconductor materials are integrated with carbonaceous graphene oxide (GO) and reduced graphene oxide (RGO). The decoration of Ag-based semiconductor components on graphene oxide having high-surface area results in binary composites with enhanced visible-light photocatalytic activity and stability. It is found that the introduction of new efficient materials further increases the effectiveness of the system. So binary and ternary composites of GO and Ag-based materials are reviewed in this paper.

Synthesis of the S/AgBr nano/micropowder in DMSO-water system

A new synthesis method of S/AgBr nano/micropowder based on sulfur and silver halide was developed. The nano/micropowder was obtained in the DMSO-water system, in two stages. Initially, sulfur was dissolved in DMSO at 120°C. The resulting solution was cooled to room temperature and separated from sulfur by filtration. Then, pre-prepared water solutions of AgNO3 and NaBr were introduced drop by drop into a sulfur solution in DMSO, at room temperature. The phase composition and structure of the precipitated powdery sediment were studied by X-ray diffraction analysis (XRD) and Raman spectroscopy. Scanning electron microscopy (SEM) was used to study the morphology and particle size. XRD showed the presence of the crystalline phase of AgBr, while the Raman spectra were characterized by the presence of sulfur and AgBr peaks. The SEM results showed that the S/AgBr is represented by oval, spherical and triangular particles of a homogeneous structure; the particle size was in the range from 300 to 800 nm.

Treatment of Wastewaters with Zirconium Phosphate Based Materials: A Review on Efficient Systems for the Removal of Heavy Metal and Dye Water Pollutants

Layered zirconium phosphate (ZrP) is a versatile material with phosphate (POH ) groups able to exchange inorganic and organic cations or to intercalate basic molecules. The present review deals with the use of this material as a sorbent for heavy metal cations or dye molecules in wastewater treatments. The possibility to combine ZrP with polymers or other inorganic materials, in order to have suitable systems for real and large scale applications, was investigated, as well as the combination with photocatalytic materials to obtain hetrogeneous photocatalysts for the capture and photodegradation of organic dye molecules.

Rapid sunlight-driven mineralisation of dyes and fungicide in water by novel sulphur-doped graphene oxide/Ag3VO4 nanocomposite

A semiconductor photocatalyst was prepared in facile, standard conditions by integrating 1% metal-free, sulphur-doped graphene oxide (sGO) as cocatalyst and Ag₃VO₄ as photocatalyst and characterised via spectroscopic, microscopic and voltammetric techniques. The catalytic activity was performed on notable water pollutants like textile dyes and fungicide employing various techniques. Cationic dyes such as methylene blue and rhodamine B were degraded > 99% with above 90% organic carbon content removal indicating total mineralisation while anionic dyes were degraded 75-80% in 1 h. For the first time, a dithiocarbamate fungicide thiram is degraded to give thiourea as a product in 1 h. Photocatalysis follows pseudo-first order kinetics with rate 3.67, 49.50 and 3.19 times higher than Ag₃VO₄, sGO and GO-Ag₃VO₄ respectively with excellent stability and recyclability. One percent sGO aided excellent carrier separation boosted by electrons and surface defects from sGO, morphology and n-n heterojunction formation. The catalyst efficiently removed 82.8% of the total organic carbon content of a real water sample from the textile mill under 2-h sunlight irradiation.