Comparative study of cationic and anionic dye removal from aqueous solutions using sawdust-based adsorbent

The treated sawdust was examined to discover its ability in adsorption of Basic Red 46 (BR46) and Reactive Red 196 (RR196). Response surface methodology was employed to evaluate the effects of initial dye concentration, solution pH, adsorbent dosage, and contact time on the process. The experimental results showed the maximum removal of 99.72 and 98.82% for BR46 and RR196, respectively. The percentage of dye removal decreased with increasing initial dye concentration. The alkaline pH for BR46 cationic dye and the acidic pH for RR196 favored the dye adsorption. The maximum removal rate was attained at the adsorbent dosage of 4 g L-1 for BR46 and 4.5 g L-1 for RR196 within the equilibrium time of 40 and 55 min, respectively. The Langmuir model best described the data with predicting the maximum adsorption capacity of 13.94 and 13.39 mgg(-1) for BR46 and RR196, respectively. Kinetic studies revealed the pseudo-second order kinetic model best fitted the experimental results, suggesting that the chemisorption controlled adsorption of both dyes onto treated sawdust. The findings revealed that the sawdust as a recycled waste could be used for efficient removal of cationic and anionic dyes from aqueous solutions. (c) 2016 American Institute of Chemical Engineers Environ Prog, 35: 1078-1090, 2016