Radiation reduction treatment and mechanism of Pb(II) ion sewage

Abstract

In this study, flame atomic absorption spectrophotometry was used to determine the change of Pb(II) ion concentration in solution before and after 60Co γ-ray irradiation; also, factors, such as the gas atmosphere, mole concentration of the initial Pb(II) ion, anion species, hydroxyl scavenger, and the effects of adding a small amount of silica sol during solid-liquid phase separation were examined to characterize their effects on the reduction treatment of wastewater containing Pb(II). The results showed that radiation-induced solvated electrons can reduce Pb(II) to Pb(0) and that the removal rate can reach 98% at an absorbed dose of 50 kGy. Nitrogen protection increased the removal rate of Pb(II) by approximately 2.5 times. The effect of the type of anion on the removal rate was negligible, but the addition of the hydroxyl radical shielding agent significantly improved the Pb(II) removal rate; the order of improvement from high to low was formic acid>isopropanol>methanol>ethanol>tertiary butanol. Additionally, due to the charge effect, the presence of low concentration (5~50 mmol/L) silica sol inhibits the reduction and removal of Pb(II). The removal rate of radiation treatment was better for higher initial concentration of Pb(II) ions. In concentrated solutions, additional pre-solvated electrons and excited state H2O** may also participate in the reduction reaction. This study provides insights for designing a feasible and optimal radiation process to treat wastewater containing lead ions.

Keywords

• wastewater treatment
• lead ion
• radiation reduction
• solvated electronics