Sorption of Chromium (VI) Using Excess Municipal Sludge

Removing or decreasing hexavalent Chromium from wastewater to the permitted levels is important due to its non-biodegradation، bioaccumulation، cancer-causing and toxic effects. In this study، biosorption of Cr (VI) from aqueous solutions by Excess Active Municipal Sludge was investigated as a function of initial Chromium (VI) concentration (in the range of 5-90 mg/l)، initial pH (in the range of 2-8)، agitation speed (in the range of 50-200 rpm)، adsorbent dosage (in the range of 2-10 g/l) and agitation time (in the range of 5-480 min) in a batch system. The optimum conditions were found by full factorial design approach. The results showed that the equilibrium time for adsorbent is 120 minutes. Also، sorption data have a good fitness by Freundlich isotherm model and adsorption kinetic is adopted with pseudo-second order model. In batch studies، at optimum condition (90 mg/l initial concentration، pH 2، agitation speed 200 rpm and adsorbent dosage 4 g/l)، the adsorption performance was about 96%; the maximum adsorption capacity was calculated about 41. 69 mg of Cr/g of adsorbent. Overall، it can be concluded that Excess Active Municipal Sludge، has a good performance as a biological، biodegradable، abundant and low-cost adsorbent for the removal of Cr (VI) from aqueous solutions.