Selection of Biosorbents for Biosorption of Three Heavy Metals in a Flow-Batch Reactor Using Removal Efficiency as Parameter
Within the last three decades, the use of low cost biosorbents like bacteria, fungi, algae and some agricultural by-products have been investigated for their biosorption capacities. In this paper, the biosorptions of three heavy metals (zinc, copper and manganese) from aqueous wastewater solution by five microorganisms (Bacillus circulans, Pseudomonas aeruginosa, Staphylococcus xylosus, Streptomyces rimosus and Saccharomyces sp.(Yeast) were investigated using a combined flow and batch processes. The biosorbents were air-dried without subjecting them to oven heat. Factors affecting biosorption capacity also known as metal uptake capacity, such as solution pH, initial ion concentration of heavy metals, mass of biosorbent and contact time were investigated. The removal efficiencies of the individual microbes were also calculated. The maximum biosorption capacities for the three heavy metals occurred at pH between 5.5 to 6.5. The biosorption of zinc ion by Staphylococcus xylosus yielded the highest removal efficiency of 94%. Also, the biosorption of copper and managense ions by Bacillus circulans produced highest removal efficiencies of 97% and 90% respectively. Initial ion concentrations of heavy metals and mass of biosorbents increase with biosorption capacity. Furthermore, Langmuir isotherm better described equilibrium biosorption of copper by Pseudomonas aeruginosa, Staphylococcus xylosus and Saccharomyces sp. (Yeast) with linear regression coefficient of correlation, R2 of 0.8646, 0.9820 and 0.9902, Freudlinch isotherm better described the biosorption of copper by Bacillus circulans and Streptomyces rimosus with linear regression coefficient of correlation of 0.7233 and 0.9290 respectively. Lastly, Langmuir isotherm better described the biosorption of manganese by Pseudomonas aeruginosa and Streptomyces rimosus with linear regression coefficient of correlation, R2 of 0.9394 and 0.9880 respectively. On the other hand, Freudlinc isotherm better described the biosorption of Manganese by Bacillus circulans, Staphylococcus xylosus and Saccharomyces sp (Yeast) with linear regression coefficient of correlation, R2 of 0.7891, 0.9753 and 0.7915 respectively.