Biosorption of Heavy Metals using Individual and Mixed Cultures of Pseudomonas Aeruginosa and Bacillus Subtilis

Abstract

Biosorption can be an effective technique for the treatment of heavy metal bearing waste water resulting from humuns and industrial activities. Several gram positive and gram negative bacteria have the ability to remove the heavy metals and there by making water contaminant free. It has been reported that attenuated bacterial biomass have greater biosorption capability than viable cells. In the present study, the biosorption of heavy metals using individual and mixed culture of attenuated bacteria (gram positive and gram negative) like Bacillus subtilis and Pseudomonas aeruginosa and parameters affecting the biosorption of heavy metals; such as time, pH, biomass concentration and initial metal concentration have been investigated. The batch experiments have been carried out using individual and mixed bacterial culture and the biosorption parameters were optimized using univariate procedures. The present study shows that 90.4% of biosorption of Mercury was observed for mixed cultures of Pseudomonas aeruginosa and Bacillus subtilis and 99.3% and 78.5% biosorption for individual cultures respectively.
The time taken for maximum sorption of Mercury was 60, 40 and 40 minutes for mixed cultures of Pseudomonas aeruginosa and Bacillus subtilis. The optimum biomass concentration was found to be 2, 0.5 and 2.5 mg/ml for mixed cultures, Pseudomonas aeruginosa and Bacillus subtilis. pH 5 was found to be optimum for all the three biomass (two individual cultures; one mixed culture) for Mercury biosorption. Optimum temperature was for all the three systems used in the present work. Adsorption
isotherms of all the three metals with mixed cultures were best fitted with Langmuir and Freundlich isotherm models having highest value of regression coefficients with R2 0.99 which is close to one. Two kinetic models namely pseudo first order equation and pseudo second order equation were also tested for the biosorption processes. The biosorption of Chromium (VI) shows that 77.6% for mixed cultures, 60.5 and 81.3 for Pseudomonas aeruginosa and Bacillus subtilis respectively. The optimum biomass concentration was found to be 1.5, 1.5 and 2 for mixed cultures (Pseudomonas aeruginosa and Bacillus subtilis) at and 3 pH. The equilibrium Arsenic biosorption were also conducted by using the same biomasses as mentioned above by achieving a sorption of 30%, 32% and 28% for mixed culture, Pseudomonas aeruginosa and Bacillus subtils).