Application of Klebsiella oxytoca biomass in the biosorptive treatment of PAH-bearing wastewater: Effect of PAH hydrophobicity and implications for prediction

Abstract

Biosorption has been widely recognized as a promising method to treat wastewater. However, few studies have investigated the impact of pollutants' properties on wastewater treatment, as well as the underlying mechanisms and future predictions. In this study, the effects of pollutants' hydrophobicity on the biosorptive removal of polycyclic aromatic hydrocarbons (PAHs) were evaluated. The results showed that the inactive biomass of Klebsiella oxytoca effectively removes PAHs from aqueous solutions with a high biosorption capacity, high biosorption affinity, and short equilibrium time. The biosorption of seven PAHs achieved equilibrium rapidly (less than 2 h) and fitted well to the pseudo-second-order kinetic model. Sorption occurred with a predominantly linear partition process to the biomaterial with Kd values of 363.11, 1719.5, 2515.5, 7343.3, 6353.4, 22,806, and 19,541 L·kg-1 for naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, pyrene, and fluoranthene, respectively. An increase in temperature led to a decrease in the biosorption affinity, and the bacterial biosorption of PAHs was spontaneous and exothermic. Furthermore, a positive correlation was observed between the sorption affinity and the octanol partition coefficient (Kow) (logKd = 1.011logKow - 0.7369), indicating that hydrophobicity is the main factor influencing the biosorption efficiency. These results suggest that biosorption is an efficient and predictable treatment for micropollutant-bearing wastewater.