Adsorption of zero-valent iron packed columns to polycyclic aromatic hydrocarbons in water

Abstract

Adsorption of polycyclic aromatic hydrocarbons (PAHs) in water using the packed column of zero-valent iron was investigated in this study. The effects of the ratio of iron powder and quartz sand, the filling height of the column, retention time and pH of PAHs solution in the column on PAH adsorption were evaluated. Furthermore, the competitive adsorption of PAHs, the maximum capacity for PAHs adsorption, iron dissolution, and recycled utilization of the column also was also investigated. The results show that the mass ratio of zero-valent iron and quartz sand was the best at 9:1. When the filling height increased, the capacity for adsorption of PAHs got greater, and the desorption of PAHs would be much more difficult. The adsorption rate increased with the retention time of PAHs solutions in the column, and then reduced gradually with the retention time. The capacity for PAHs adsorption was stronger under neutral or alkaline conditions, but was weaker under the acid system. When multiple PAHs were mixed together, the competitive adsorption of PAHs was obvious at high concentrations, but not evident at low concentration. The adsorption rates of the high-ring PAHs were higher than those of the low-ring PAHs. Maximum capacity for PAHs adsorption in water reached at 0.015 g·g-1. When the mass content of PAHs was 25 μg, the penetration volume of water was up to 4 L. The packed column was re-activeted with 0.1% H2O2 under the acidic system, and the variability of adsorption rate was less than 3% when it was reused. Therefore, it is an effective way of removing PAHs from water by the packed column of zero-valent iron, which may have a better prospect in large-scale application.