Biological preparation and application of poly-ferric sulfate flocculant

A novel inorganic polymer flocculant, poly-ferric sulfate (BPFS) was prepared by oxidation of ferrous sulfate using domestic Thiobacillus ferrooxidans (T·f) under acid condition. The optimal conditions for the preparation were pH value of 1.5, (NH4)2SO4 dosage of 0.5 g/L, initial Fe2+ concentration of 45g/L, inoculum 10%, rotating speed of 120 r/min, reaction time of 5-6 d and reaction temperature of 30 °C. Under the optimal conditions, the BPFS product with pH value of 1.5-2.2, basicity of 17.5%-22.7% and total iron content of 43.87-45.24 g/L was obtained. The application of the BPFS to three wastewaters was carried out, and the removal efficiencies of COD, decolorization and Zn2+ by BPFS can be reached 70%, 90% and 99%, respectively. The result suggests that the BPFS is an excellent flocculant for water treatment.