Optimization of process variables for hexavalent chromium biosorption by psychrotrophic Pseudomonas putida SKG-1 isolate

Abstract

Hexavalent chromium, a priority pollutant, is well known for its carcinogenicity, mutagenicity, and teratogenicity in humans, animals, and plants. Biosorption is an attractive technique for the treatment of chromium pollution. This study was aimed to optimize the effect of various process parameters on biosorption of Cr⁶⁺ by Pseudomonas putida SKG-1 employing conventional one-factor-at-a-time and response surface methodology (RSM) approaches in a batch process. In conventional method, the maximum Cr⁶⁺ biosorption (97%) was achieved at 6.0 g dead cell biomass l⁻¹, pH 3.0, and 35°C during 195 min contact time with an initial Cr⁶⁺ concentration of 50 mg l⁻¹ under shaking (150 rpm). Whereas in RSM approach, a slightly enhanced Cr⁶⁺ biosorption (98%) was obtained only in 180 min by P. putida cells (8.0 g l⁻¹). The correlation coefficient (R²) of biosorption data to Cr⁶⁺ simulated by the Langmuir, Freundlich, and D–R isotherm models was 0.9953, 0.8482, and 0.8916, respectively. The best fit was obtained for Langmuir model which suggests the binding of chromium as a monolayer on the surface of the biomass.

Keywords:

• Pseudomonas putida
• Biosorption
• Chromium
• Correlation coefficient
• RSM