Effect of method of treatment of rice husk on adsorption of textile dyes from aqueous solutions

Abstract

Adsorption of textile dyes onto rice husk based adsorbents was studied. Batch experiments were conducted to determine the effect of method of treatment of rice' husk on adsorption of Basic Green 4 and Acid Blue 80 from aqueous solutions. Rice husk (RH) obtained from ten varieties of paddy were tested. Raw rice husk, chemically or thermally treated rice husk were tested for adsorption. The maximum adsorption was observed at solution pH values above 6 for Basic Green 4 and below 3 for Acid blue 80. .The adsorbent to solution ratio, solution dye concentration and adsorbent particle size affect the degree of dye removal. Carbonizing at 700°C for I hr was observed as the optimum condition for thermal activation. Sodium hydroxide treated RH and carbonized RH showed high adsorption capacities compared to acid treated RH, oxidized RH and raw RH. Basic green 4 dye showed high adsorption compared to acid blue 80 for all the varieties of RH based adsorbents tested. RH based adsorbents were compared with the commercial activated carbon. Adsorption capacities for Raw RH, NaOH treated RH, Thermally treated RH and Granular Activated Carbon were 5.8, 7.5, 7.5 and 7.4 for Basic green 4 and 3.4, 6.1,6.5 and 6.5 mg of dye/g of adsorbent for Acid Blue 80 respectively. Kinetic data were fitted to the Pseudo second order model and initial adsorption rates and rate constants were determined.