Adsorption of brilliant green dye in aqueous medium using magnetic adsorbents prepared from rice husk ash

Abstract

Large scale production and extensive application of synthetic dyes in the textile industry have caused considerable environmental pollution. The treatment of colored effluents using efficient technologies, are sought after due to this concern. This research evaluates the effectiveness of magnetic adsorbent (MRHA) prepared from rice husk ash (RHA) by a chemical processing method to remove brilliant green (BG) dye from an aqueous medium. The resulting MRHA adsorbents were tested at different initial concentration of 5–400mg/L, adsorbents amount of 0.5–2.3g, shaking rate of 50–300rpm, contact time of 15–120 min, pH of 3–11, and temperature of 27–60 C. A maximum removal of 96.65% was obtained at initial dye concentration of 200mg/L, adsorbents amount of 2g, shaking rate of 150rpm, contact time of 60min, and temperature of 50 C. The fresh and spent MRHA adsorbents were analyzed through scanning electron microscopy (SEM) and particle size distribution. The particle analysis of the fresh and spent adsorbents indicated bimodal pore size of 90 and 900 µm, respectively. The adsorption behavior of the adsorbent followed those of the Langmuir, Freundlich, and Temkin isotherm models. However, Temkin isotherm model displayed the best fit with the coefficient of determination, R2 of 0.811, suggesting a strong interaction, equivalent to that of chemical absorption between BG dye molecules and the surface of MRHA adsorbent for effective removal of BG dye from the aqueous medium. The magnetic character of the adsorbents allowed the spent sample to be isolated successfully and conveniently by using an external magnetic field.