Abstract
A novel inorganic polymer flocculant, biopolymeric ferric sulfate (BPFS), was prepared by immobilization technology of microorganisms and by oxidation of ferrous sulfate using domestic Thiobacillus ferrooxidans (T. f) under acidic condition. T. f was isolated on the agarose single-plate medium, which exhibited an unusual trait on the utilization of low concentration of the nitrogen source and phosphorus as the nutrient substance. Under the optimal conditions, the microorganism could grow and reproduce normally and maintain the strong catalytic oxidation activity to Fe2+. The immobilization of T. f on the polyurethane as the support matrix was investigated. Cycling batch operation was applied to the preparation of 40 kg/m3, 60 kg/m3, and 80 kg/m3 BPFS when the optimal conditions are pH value of 1.8, circulation flow rate of 0.28–0.30 L/h, and reaction temperature of 28 ± 1°C. When the prepared BPFS and SPFS (solid biopolymeric ferric sulfate) were used to dispose Songhua River water, the removal rate of turbidity and CODMn of BPFS was slightly better than that of SPFS. The removal efficiencies of turbidity and CODMn by BPFS could reach 93.9% and 79.7%, respectively. The result suggests that the BPFS has good flocculating activity.
Highlights
An important inorganic macromolecule flocculant, polymeric ferric sulfate (PFS) is mostly prepared by direct oxidation of ferrous sulfate using strong oxidants such as H2O2, KClO3, NaClO, and HNO3 or by catalytic oxidation of ferrous sulfate using NaNO2 or NaI as a catalyst in the acid media [1,2,3,4,5,6,7]. ese production methods are under harsh production conditions, long period, high cost, and oxidant residue resulting in serious corrosion on the dosing system [8]
Iobacillus ferrooxidans is strictly autotrophic organisms, and most of the chemoautotrophic organisms are highly sensitive to organic compounds, such as polysaccharides and other components in agar. e small molecules are produced by the agar under acidic condition
Saccharomycetes can metabolize the small molecules produced by the agar and inhibit the growth of T. f on the solid medium. erefore, the modi ed solid medium used agarose instead of agar to gel solidify the medium, and this can support the growth of most strains [19, 20]
Summary
An important inorganic macromolecule flocculant, polymeric ferric sulfate (PFS) is mostly prepared by direct oxidation of ferrous sulfate using strong oxidants such as H2O2, KClO3, NaClO, and HNO3 or by catalytic oxidation of ferrous sulfate using NaNO2 or NaI as a catalyst in the acid media [1,2,3,4,5,6,7]. ese production methods are under harsh production conditions, long period, high cost, and oxidant residue resulting in serious corrosion on the dosing system [8]. E product called biopolymeric ferric sulfate (BPFS) was prepared by catalytic oxidation of microorganisms. BPFS has good turbidity and COD removal, its preparation conditions are mild, production costs are low, the process is no pollution, and microbial secretions can play a secondary flocculation [9]. T. f has been widely utilized in the processes of bioleaching, the desulphurization of coal and environmental pollution control. T. f has been widely utilized in the processes of preparation of BPFS at normal temperatures and pressures [13]. The methods of preparation of BPFS by biocatalytic oxidation have many advantages such as wide sources of raw materials and easy operation, but the easy loss of bacteria leads to the low utilization rate of bacteria and production efficiency and the long period
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