Removal of Cr(VI) by Sewage Sludge Based Activated Carbons Impregnated with Nanoscale Zero-Valent Iron

Sewage sludge based activated carbons impregnated with nanoscale zero-valent iron (nZVI) were synthesized and used for the Cr(VI) removal from water. Pyrolysis conditions for preparing sewage sludge based activated carbon were evaluated, with optimized conditions being pyrolysis temperature of 600 degrees C, pyrolysis time of 30 min and 3 M zinc chloride. The activated carbon thus prepared had a BET surface area of 968.2 m(2)/g. A series of nZVI-impregnated activated carbons with varied Fe/C ratios were then synthesized and their capacities in removing Cr(VI) were evaluated. The synthesized sorbent having a Fe/C mass ratio of 1: 1 was found to have the best performance. Batch equilibrium tests indicate that the sorbent had a maximum capacity of 42.0 mg/g for Cr(VI) removal at pH 5, and 32.0 mg/g at pH 7. The kinetics of Cr(VI) removal at pH 5-9 was also studied, with lower pH values found favoring Cr(VI) removal. Findings of this study suggest that nZVI-impregnated activated carbon prepared from sewage sludge would be a promising sorbent material for reductive removal of Cr(VI) from water.