ADSORPTION OF Cr (VI) FROM AQUEOUS SOLUTION BY SLUDGE-BASE ACTIVATED CARBONS OBTAINED FROM CHEMICAL AND PHYSICAL ACTIVATION

Activated carbons were developed from sewage sludge by chemical and physical activation. It was found that chemical activation can produce carbons with better textual structures, which is more favorable for Cr (VI) uptake compared with those produced by physical activation. The analyses of N-2/77K adsorption isotherm methods showed that chemical activation can make activated carbons with relative larger S-BET surface area and higher porosity. FTIR results revealed functional groups presented on both kinds of carbons' surface, which were responsible for Cr (VI) adsorption. The adsorption capacity was investigated on adsorbent dosage, solution pH, contact time, solution concentration and reaction temperature. The data showed that Cr (VI) removal was highly pH-dependent. The maximum adsorption of Cr (VI) for both carbons was achieved at pH 3.0. The adsorption process fitted pseudo-second-order kinetics well and the equilibrium was reached after 4 h reaction. Equilibrium data was described by the Langmuir isotherm model and the maximum adsorption capacity of Cr (VI) by ACC (chemical activated carbon) was 38.168 mg/g at 50 degrees C. It was much higher than ACP (0.079mg/g) which was produced by physical activation.