ZnO nanoparticles immobilized on the surface of stones to study the removal efficiency of 4-nitroaniline by the hybrid advanced oxidation process (UV/ZnO/O3)

4-Nitroaniline (4-NA) is one of the common pollutants in wastewater. Because of the toxicity, carcinogenicity and mutagenicity, it has been reported as priority pollutants. The purpose of this study was to synthesize ZnO nanoparticles and its immobilization on the surface of stones to study the removal efficiency of 4-NA by the hybrid advanced oxidation process (UV/ZnO/O-3). The SEM, TEM and XRD analyzes were used to investigate the physiochemical properties of nanoparticles. The effective parameters on the process including the initial pH of the solution, contact time, dose of immobilized nanoparticles, the initial concentration of 4-NA, were investigated. The kinetics of the degradation reactions were determined. Data analysis was performed using SPSS-16 software. By increasing the catalyst dose from 1 to 3 g/L, the removal efficiency increased from 75% to 92%. The highest 4-NA removal efficiency of 96% was achieved by hybrid advanced oxidation process (UV/ZnO/O-3) in optimal conditions including pH: 5-7, the dose of immobilized ZnO: 3 g/L, the initial concentration of 4-NA: 10 mg/L and contact time: 60 min. Therefore, this process is recommended for the removal of resistant and toxic pollutants from aqueous solutions with a relatively high efficiency. (C) 2018 Elsevier B.V. All rights reserved.