Biosorption of Azo Dye (Maxilon Red and Everzol Red) on to Natural and Modified Waste Sludge

A wide range of technologies has been developed for the removal of dyes from wastewaters to decrease their environmental impact. Wastewater containing dyes is generally treated using more than one process such as adsorption/biosorption. In this study, effects of initial pH (2-8), initial azo dye concentration (Co:25-200 mg/l), contact time (tc:2.5-1440 min) and amount of waste sludge (m:1-15 g/l) were studied by natural and modified dried waste aerobic sludge (WS) in a lab-scale batch study and also optimized by employing response surface methodology (RSM)-Box-Behnken Model for Maxilon Red GRL(MRGRL) and Everzol Red (ER) removal from wastewaters. The optimum experimental conditions were found to be pH=5, Co= 112.5 mg/l, tc= 180 min. and m= 15g/l for dyes and MRGRL and ER removal was determined as about 97% and 95.85%, respectively. The results clearly showed that amount of WS and contact time are the most important parameters for color removal.
FTIR and SEM (scanning electron microscope) images were used to understand morphology and structural character of WS and after biosorption process. D-R biosorption isotherm model was used in order to determine type of biosorption mechanism. The E value of D-R isotermisotherm model was found to be 7.071 for both dye. Pseudo-second order and intraparticle diffusion (Weber-Morris) models were suitable for biosorption kinetics. 0,1 M HCl and NaOH were used for desorption studies. Effect of ionic strength (NaCl) was not observed between 0,5-1 mol/L NaCl on to biosorption efficiency. WS (biowaste), Natural or modified, one of the low-cost biosorbent, can be used for removal of azo dye from wastewaters.