Synthesis of Ag/ZnO-AC composite photocatalyst: spectroscopic investigation, parameter optimization, synergistic effect and performance enhancement for cost-effective photocatalytic degradation of phenols and dyes

Abstract

A ternary photocatalyst composite-Silver decorated on ZnO supported with activated carbon (Ag/ZnO-AC) was investigated for the synthesis, characterization and UV assisted photocatalytic degradation of phenols and dyes present in wastewater. XPS and TEM revealed the elemental composition and formation of ternary Ag/ZnO-AC composite. Different operational parameters including the effect of calcination temperature, catalyst dose, initial concentration of pollutant and the effect of H2O2 and ethanol were studied. The photocatalytic activity was assessed for the degradation of p-Nitrophenol (PNP), o-Nitrophenol (ONP), and dye methyl orange (MO) under UV irradiation by ZnO, Ag/ZnO and Ag/ZnO-AC catalyst. The degradation for PNP, ONP and MO in presence of UV light were found to be in the order Ag/ZnO-AC>Ag/ZnO>ZnO. Improved degradation by Ag/ZnO-AC is attributed to high charge separation and greater adsorption of pollutant because of the combination of Ag and AC leading to a synergistic effect in the catalyst. Along with the high reusability, the composite catalyst Ag/ZnO-AC was found to be non-selective and cost-effective for the degradation of phenols as well as dyes. The as synthesized ternary composite Ag/ZnO-AC can be efficiently used as a photocatalyst for the degradation of recalcitrant and other deleterious contaminants present in wastewater.

Effect of Doping ZnO on Activated Carbon Prepared from Waste Paper for Photocatalytic Applications

“…In a study conducted by Ma, et al ( 2015), this reaction occurred at a temperature of 360˚C which was indicated by the appearance of the compound Zn2OCl2.2H2O identified by the sharp peak of XRD at 2θ is 11.2˚ and detected ZnO peak at 2θ between 30˚ to 40˚ followed up to 59.7•, this indicates the decomposition of Zn2OCl2.2H2O that can occur further when the temperature is increased to 600˚C, where the evaporation of ZnCl2 occurs with the following reaction taking place on eq. ( 4) and (5).…”

“…The majority of waste paper originates from wood or cotton pulp, primarily composed of cellulose fibers (constituting 90-99%), which are rich in carbon, possess a distinctive pore structure, and feature functional groups such as carboxylic and hydroxyl groups [4]. Addressing the mitigation of pollutants carried by effluents requires effective adsorbents like zeolites, activated carbon, activated alumina, silica gel, among others [5]. Activated carbon is particularly favored due to its commendable performance.…”

“…The semiconductor that is often trusted to be used in various applications including water treatment is ZnO nanoparticles with the advantages of low price, wide band gap of 3.37 EV, high stability, environmentally friendly, and reusable [5]. However, due to the size and weak compatibility of ZnO causing aggregation and one of its lack is the low charge separation efficiency [15].…”