Combined biological and chemical oxidation of ferrous sulfate using immobilised Thiobacillus ferrooxidans

Thiobacillus-ferrooxidans immobilised in biomass support particles with act ivated carbon coating were used in a packed-bed bioreactor to study the com bined effects of chemical and biological catalysis on the oxidation of ferr ous iron. The effect of ferrous iron concentration (in the range 530 kg m(- 3)) and of its volumetric loading on the kinetics of reaction were investig ated. With low concentrations of ferrous iron, 5-10 kg m(-3), the combined catalysis did not offer a significant advantage to oxidation of ferrous iro n and the kinetics of reaction were slightly faster than those achieved wit h just the biological catalyst. With ferrous iron at a concentration of 20 kg m(-3), the combination of chemical and biological catalysis resulted in a remarkable enhancement of the reaction rate. The maximum oxidation rate o f ferrous iron in the presence of combined catalysts, 21.9 kg m(-3) h(-1), was twice as high as that achieved with just the biological catalyst. (C) 1 999 Society of Chemical Industry.