STATISTICAL OPTIMIZATION FOR COMPETITIVE BIOSORPTION OF REACTIVE ORANGE 13 AND REACTIVE BLUE 222 BY Rhizopus arrhizus: EQUILIBRIUM ISOTHERMS AND KINETIC STUDIES

This study employed sequential statistically designed experiments for studying the competitive biosorption of Reactive Orange 13 and Reactive Blue 222 from aqueous solution by utilization of dead biomass of Rhizopus arrhizus as an economical fungal biosorbent. Plackett - Burman design was used in the first step to identify the most significant factors influencing biosorption of dyes. Response Surface Methodology was adopted in the second step to identify conditions that would generate maximum biosorption. ANNOVA for both the dyes indicated that the second-order polynomial models were highly significant with P< 0.0001 and high values of coefficient of determination. The maximum sorption (93.76% for Reactive Orange 13 and 97.83% for Reactive Blue 222) was achieved under following conditions: pH 2.5; dye concentration 100 mg L-1; biosorbent dosage 1.7 g L-1; temperature 35°C; speed of agitation 80 r min-1 and contact time 120 min. Kinetics and isotherm evaluations were conducted using the time dependent removal of color by the biosorbent. The mechanism of biosorption was revealed by FTIR, XRD and BET analysis. This work demonstrated the feasibility of employing Rhizopus arrhizus as an effective biosorbent for the removal of dyes from a binary mixture.