Valorization of secondary resources into silica-based adsorbents: Preparation, characterization and application in dye removal from wastewater

Abstract

Low-cost silica, magnetite, and magnetic silica were prepared using corn cob and spent pickle liquor. To enhance the adsorption characteristics, the extracted silica was heat-treated and the ratio of silica:magnetite was optimized. A detailed characterization of the prepared materials was conducted and the adsorption characteristics were also inclusively assessed.The characterization study disclosed that the prepared materials were nanosized, nonporous, and forms large aggregates with inter-particles voids. The prepared silica was amorphous and heat treatment of extracted silica increased the specific surface area greatly. The superparamagnetism and consequent magnetic separability is an advantage of magnetic silica. The adsorption study showed that the optimum silica:magnetite ratio, solution initial pH, and adsorbent dosage were 1:10, 3 and 2 g/L, respectively. The adsorption kinetics obeyed the pseudo-second-order equation while the adsorption isotherm was best described by Langmuir model. Magnetic silica provides a balance between the adsorption capacity (19 mg/g) and magnetic separation possibility after wastewater treatment. Amongst the different prepared materials, heat-treated silica achieved the highest adsorption capacity (44 mg/g) toward RhB and was better than many other adsorbents reported in the literature.