Modeling of PAHs adsorption on Thai clay minerals under seawater solution conditions

PAHs adsorption in the aquatic environment is strongly influenced by sediment properties and water conditions. To determine how these factors are responsible for PAHs adsorption kinetics, we evaluated the influence of clay mineral type, and varied pH, temperature, and salinity of the solution on PAHs adsorption by using benzo[a]pyrene, B[a]P, as the representative PAHs. Overall, we found that B[a]P adsorption on montmorillonite was about 2 times higher than on kaolinite. This may be caused by the higher surface area of montmorillonite. For the influence of water conditions, the results clearly indicated that B[a]P adsorption increases with a decrease in solution pH and an increase in salinity, due to increased protonation of acidic groups. As B[a]P water solubility decreases with water temperature, B[a]P adsorption on clay particles increases. The equation should be written as a classical distribution ratio definition. All of these influencing factors can be summarized in the following equation: C-s/C-w = 1/3 * ( Kp(pH) + Kp(t) + Kp(S)) * S-a where C-s and C-w are the B[a]P concentrations in the clay mineral and solution, S-a is the surface area of clay mineral, and Kp(pH), Kp(t), Kp(S) are the Kp values for different solution pH, water temperature, and water salinity, respectively. (C) 2013 The Authors. Published by Elsevier B.V.