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

Document Type: Original Research Paper

Authors

1 Department of Biotechnology & Bioengineering CINVESTAV-IPN, Instituto Politécnico Nacional 2508, San Pedro Zacatenco, 07360 México, D.F.

2 Chemical and Biochemical Engineering Division, Tecnológico de Estudios Superiores de Ecatepec, Tecnológico, 55210, Valle de Anáhuac, Ecatepec de Morelos, Estado de México

Abstract

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

Keywords