Kinetics of Biosorption of Three Heavy Metals by Five Free Microorganisms

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In this paper, kinetics of biosorption of three heavy metals by five microorganisms was studied. The three heavy metals are zinc copper and manganese while the microorganisms are Bacillus circulans, Pseudomonas aeruginosa, Staphylococcus xylosus, Streptomyces rimosus and Saccharomyces cerevisiae. The investigation was carried out using non-vibrational flow-batch process. Two models were proposed to fairly accommodate all the mechanisms of biosorption at longer contact time. Also, the equation of a completely mixed flow was used to study the biosorption rate constant of the microorganisms within the detention time of 25 minutes inside the treatment units. Part of the data obtained from the laboratory was used for the calibration of the models while some parts were used for the verification. The verification was assessed using linear regression coefficient of correlation and average relative error. During the verification, the values of linear regression coefficients for the two models are 0.9978 and 0.9992 while average relative errors are 0.8768% and 4.4126% respectively. When compared with pseudo first and second order models, the values of coefficient of correlation obtained are 0.9965 and 0.9451 with corresponding average relative errors of 36.74% and 28.53% respectively. The values of biosorption rate constants for the microorganisms obtained from completely mixed equation are higher than those of concentration based models showing that the rate of biosorption is higher within the inception than towards equilibrium.