Ag–AgBr/CaWO 4 composite microsphere as an efficient photocatalyst for degradation of Acid Red 18 under visible light irradiation: Affecting factors, kinetics and mechanism

Photocatalytic degradation of Acid Red 18 by synthesized AgCoFe2O4@Ch/AC: Recyclable, environmentally friendly, chemically stable, and cost-effective magnetic nano hybrid catalyst

Chitosan (Ch) is a linear biodegradable natural carbohydrate polymer and the most appealing biopolymer, such as low-cost biodegradability, biocompatibility, hydrophilicity, and non-toxicity. In this case, Ch was utilized to synthesize AgCoFe2O4@Ch/Activated Carbon (AC) by the modified microwave-assisted co-precipitation method. The physical and chemical structure of magnetic nanocomposites was analyzed and characterized by Field Emission Scanning Electron Microscope (FESEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Energy Dispersive Spectroscopy (EDS), Diffuse Reflection Spectroscopy (DRS), Value stream mapping (VSM), Fourier transform spectroscopy (FTIR) and BET. The effects of various parameters on the removal of dye (Acid Red18), including catalyst dose, dye concentration, pH, and time were studied. Results showed that the highest removal efficiencies were 96.68 % and 84 % for the synthetic sample and actual wastewater, respectively, in optimal conditions (pH: 3, the initial dye concentration: 10 mgL-1, the catalyst dose: 0.14 gL-1, time: 50 min). Mineralization, according to the COD analysis, was 89.56 %. Photocatalytic degradation kinetics of Acid Red 18 followed pseudo-first order and Langmuir-Hinshelwood with constants of kc = 0.12 mg L-1 min-1 and KL-H = 0.115 Lmg-1. Synthesized photocatalytic AgCoFe2O4@Ch/AC showed high stability and after five recycling cycles was able to remove the pollutant with an efficiency of 85.6 %. So, the synthesized heterogenous magnetic nanocatalyst AgCoFe2O4@Ch/AC was easily recycled from aqueous solutions and it can be used in the removal of dyes from industries with high efficiency.

Synthesis of CaWO4 as a Photocatalyst for Degradation of Methylene Blue and Carmine under Ultraviolet Light Irradiation

Photocatalysis is considered a promising method for wastewater treatment; however, most synthesized photocatalysts have complex structures and are costly. Thus, in this study, a novel CaWO4 sample was synthesized by a co-precipitation method in one step. The characteristic results show that CaWO4 has good dispersibility, a large specific surface area, and good photoresponse under UV light. The synthesized CaWO4 can be used to degrade methylene blue (MB) and carmine (CR) under UV light without the addition of oxidants. The effects of a water matrix, including pH value, solid–liquid ratio, light intensity, and initial concentration of pollutants on photocatalytic degradation were studied. According to the optimization of these factors, the optimal photocatalytic degradation condition was found under the catalyst concentration of 1.0 g/L and ultraviolet light intensity of 80 W. The optimal pH is 8.2 for the MB system and 6.0 for the CR system. The optimal photocatalytic degradation of MB and CR at 100 mg/L can be achieved as 100%. According to the results of scavenger experiments, holes and hydroxyl radicals dominate the degradation of MB while hydroxyl radicals and superoxide anions are mainly responsible for the degradation of CR. Further analyses showed that photogenerated electrons generated on the surface of the CaWO4 can form electron–hole pairs, thereby producing hydroxyl radicals and superoxide anions to degrade dyes. In addition, the CaWO4 has a good cycling performance in the process of degrading MB (more than 80% after five cycles). It provides a new idea for the photocatalytic degradation of dyes using mineral-like materials.

Green calcium-based photocatalyst derived from waste marble powder for environmental sustainability: A review on synthesis and application in photocatalysis

Calcium, with its excellent adsorptive property and higher permissible limits in the environment, emerges as an effective wastewater treatment earth metal. Most of the catalysts, photocatalysts, and adsorbents reported in the literature have heavy metal complex, which creates a leaching problem. Majorly, precursors used for the synthesis of heterogeneous catalysts for wastewater treatment are costly. Therefore, the use of such precursors would be not suitable and feasible approach from an economic point of view. This review work is focused on giving an overview of the utilisation of calcium-based catalysts (adsorbents and photocatalyst) for the removal/degradation of various types of dye water pollutants and summarises the reported effects of calcium as a base on the removal efficiency of dopants. In this article, an extensive literature survey is presented on the various photocatalysts developed and the different syntheses involved in their preparation. As the utilisation of marble powder is a green sustainable approach, the scope of various calcium-based photocatalysts and their application is presented. This article also aims for the elementary and inclusive determination of the effect of introducing calcium as a base for different catalysts and adsorbents.

Synthesis and antibacterial activity of silver@carbon nanocomposites

In this work, hollow multiple-Ag-nanoclustes- C-shell nanocomposites (Ag@C) were synthesized by using silane coupling agent to graft carbon dots (CDs) with silver nanoparticles (AgNPs). CDs act as coating and stabilizing agent, protecting AgNPs from aggregation and oxidation. The resulting Ag@C nanocomposites demonstrate strong bactericidal effect against both gram-negative and gram-positive bacteria in the disk diffusion test. Cellular toxicity evaluation was performed using MTT assay. Meanwhile, the as-prepared Ag@C nanocomposites show a good biocompatibility.

Sheet-on-sphere structured Ag/AgBr@InVO4 heterojunctions and enhanced visible-light photocatalytic activity

Sheet-on-sphere Ag/AgBr@InVO₄ displayed excellent photocatalytic degradation of RhB, which was attributed to enhanced visible-light absorption and anti-combination of electrons/holes through it's heterostructure.

One-pot synthesis of Ag-modified LaMnO3–graphene hybrid photocatalysts and application in the photocatalytic discoloration of an azo-dye

Ag-modified LaMnO₃–graphene nanocomposites possess excellent photocatalytic activity for Direct Green BE photodegradation and the active hole generated in Ag/LaMnO₃–graphene plays a key role.