Sequential Precipitation of Heavy Metals Using Sulfide-Laden Bioreactor Effluent in a pH Controlled System

Sulfide produced in an ethanol fed anaerobic baffled reactor, was utilized to precipitate metals separately in a pH controlled system. Sulfide produced in the reactor (780 +/- 27 mg/L S2-) was transported with N-2 gas to the metal precipitation chamber at pH 2.5 to precipitate Cu2+ separately from Fe2+. Cu precipitation was completed at 98% efficiency within 5 min. The remaining Fe2+ was then precipitated at elevated pHs by mixing the reactor effluent. XRD patterns of the precipitates showed that copper was precipitated in the form of CuS with a particle size of 14-22 nm whereas iron was precipitated as FeS with 32-85 nm particle size.