Studies on the Removal of Cationic Dyes from Aqueous Solution by Mixed Adsorbents

Studies on the (FA) removal of cationic dyes from aqueous solution by adsorption on low cost mixed adsorbents, namely flyash, bagasse (BG) and rice husk (RH) as an adsorbent and blending (mixing) them with bentonite. The modifications and combinations of sorbents to form bentonite blended decolourizers enhanced sorption capacity of sorbents by 10 to 20%. The effect of various parameters affecting the adsorption such as initial dye concen tration, adsorbent dose and pH were determined. Adsorption decreases with rise in dye concentration but increases with increases in adsorbent dose. The maximum removal was with FA: 69.0% CV, 64.1% MB and 63.6% MG at dye concentration 10 mg/L, sorbent dose 10 g/L, at pH 7.5, temperature 25 o C, contact time 5 h and rpm 150. Under the same conditions RH.: was found to remove 62.2% CV, 53.9% MB and 49.3% MG. The order of dye removal capacities for these chemical (mixed) adsorbents was found FA > BG > RH. The order of removal/sorption of dyes was CV > MB > MG. The optimum pH was 7.5 for all the dyes under investigation. Thus, alkaline medium favours the dye removal.