含Pb(Ⅱ)废水的辐射还原处理及其机制

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

通过火焰原子吸收分光光度法测定60Coγ射线辐照前后溶液中Pb(Ⅱ)离子浓度变化,研究不同因素(如气体氛围、初始Pb(Ⅱ)离子的物质的量浓度、阴离子种类、羟基清除剂、固-液分相中少量硅溶胶添加等)对含Pb(Ⅱ)废水的还原处理效果。结果表明:辐射诱导的溶剂化电子能够将Pb(Ⅱ)还原成Pb(0),去除率在吸收剂量为50 k Gy时可达98%,吸收剂量为20 k Gy时,氮气的保护可提升Pb(Ⅱ)去除率最大约2.5倍;阴离子的种类对去除率的影响可忽略,但羟基自由基屏蔽剂的加入显著提升了Pb(Ⅱ)的去除率,且提升效果顺序由高到低为甲酸>异丙醇>甲醇>乙醇>叔丁醇;此外,由于电荷效应的影响,低浓度(5~50 mmol/L)硅溶胶的存在抑制了Pb(Ⅱ)的还原去除;初始Pb(Ⅱ)离子浓度越高越有利于提高辐射处理的去除率,在浓溶液中,额外的预溶剂化电子和激发态H2O**也有可能参与了还原反应。本研究为采用辐射技术处理含Pb(Ⅱ)废水的可行性与工艺优化提供了数据和理论支撑。

In this study, flame atomic absorption spectrophotometry was used to determine the change of Pb(Ⅱ)ion concentration in solution before and after60 Co 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.