RSM Optimization of Direct Orange 26 Adsorption on Low-Cost Silica Fume Adsorbent

Abstract

Today, dye pollutants enter resources of water through various industries. Due to the stability and carcinogenicity of dye pollutants, it is necessary to treat colored wastewater before entering the aqueous cycle. One of the important methods for wastewater treatment is adsorption. In this study, the effect of industrial waste of silica fume adsorbent on azo dye Direct Orange 26 (DO26) was investigated. Design of experiment was carried out with CCD method by using Design Expert software version 7 to model and investigate the effects of parameters pH, concentration, amount of adsorbent, and time. The model proposed by the software is a second-order model. According to the findings, important and effective parameters for the quadratic model of experimental design were obtained from ANOVA (analysis of variance). The optimum conditions for the maximum removal of DO26 (95.26%) were obtained to be at pH 2.01, contact time of 55.15 minutes, adsorbent amount of 0.2 g, and initial concentration of 44 ppm. The experimental kinetic data were analyzed through the conventional kinetic models, and the results demonstrate that the sorption kinetics can be accurately described by the pseudo-second order model. Also, based on FESEM image, silica fume has a spherical and porous structure, therefore, silica fume can remove dye pollutants from water as a cheap adsorbent.