Biosorption of Priority Pollutants of Petroleum Refinery Wastewater

Heavy metals and organic materials pollution in the aquatic system have become a serious threat today. Zinc, phenol and naphthalene are common environmental contaminants. The fate and transport of these chemicals must be sufficiently understood to predict detrimental environmental impacts and to develop technically and economically appropriate remedial action to minimize environmental degradation. In this study, microbial biomass has emerged as an option for developing economic wastewater treatment. Dead algal biomass may passively sequester metals and organic materials by the process of biosorption from dilute solutions, where biomass functions as an ion exchanger by virtue of various reactive groups available on the cell surface such as, carboxyl. This biosorption technology has advantages of low operating cost. The potential use of blank alginate beads, and immobilized dead algal cells for the removal of zinc, phenol and naphthalene from aqueous solutions was investigated. It was found that the biosorption capacities were significantly affected by solution pH. Dynamic and isotherm experiments were carried out at the optimal pH 5.0, 11.0 and 4.0 for zinc, phenol and naphthalene, respectively. The zinc removal rate was rapid and the maximum zinc uptake occurred within the first 30 min in both cases of blank alginate and immobilized algal cells. On the other hand, the equilibrium uptake was attained within the first 5 min in the case of phenol and naphthalene. The equilibrium data for the biosorption of zinc ions, phenol and naphthalene onto both sorbents could be adequately fitted by to the Langmuir, Freundlich, and Dubinin-Radushkevich (DR) isotherm equations. It was also found that the presence of other pollutants, such as citric acid, decreased the uptake of zinc, phenol, or naphthalene, and this increase was function of the other pollutant concentration. The sorption of zinc ions, phenol or naphthalene from refinery simulated wastewater was found to follow pseudo-second order kinetics