A mathematical Model for Cadmium Removal using A sulfate Reducing Bacterium: Desulfovibrio alaskensis 6SR

Abstract

In this work, an unstructured-type mathematical model was developed to simulate<br />cadmium (Cd2+) removal by Desulfovibrio alaskensis 6SR, which is a recently described sulfate<br />reducing bacterium, whose capacity for removing heavy metals are being studied. Three processes<br />are considered in the model: 1) the sulfate reduction process, 2) the consumption of lactate as<br />carbon source, and 3) the metal removal. The model was tested with different initial Cd2+ concentrations<br />(50, 100, 170, and 190 mg/L), and it accurately predicted the behavior of experimental data with<br />satisfactory correlation coefficients (R2>0.97). In addition, the model showed that the H2S production<br />rate and initial concentration of Cd2+ are key operating variables in a bioreactor. Desulfovibrio<br />alaskensis 6SR was able to remove more than 99.9% of cadmium in a batch process, where the initial<br />concentration was 170 mg/L. The model, applied to a continuous process, predicted a maximum Cd2+<br />removal of 99.1% with the same initial concentration. Also, the model predicted the inhibitory effect<br />of initial Cd2+ concentrations above 190 mg/L. The mathematical model developed can be used for<br />optimization and control purposes.