还原条件下氧化石墨烯对铅离子的吸附/解吸附性能

Adsorption and desorption of lead on graphene oxide surface under reduction condition

针对地下水还原条件下附着Pb离子氧化石墨烯(GO)纳米颗粒的环境稳定性,实验研究了厌氧条件下Na_2S还原对GO吸附Pb^(2+)以及解吸附过程的影响.采用X射线光电子能谱、傅里叶变换红外光谱、X射线衍射以及表面增强拉曼技术对吸附与解吸附的过程机理进行分析比较.结果表明,GO及Na2S还原生成r GO对Pb^(2+)的吸附过程符合Langmuir吸附模型,最大吸附容量分别为937.65、92.99 mg·g^(-1),GO还原后Pb^(2+)吸附容量减小;厌氧条件下Na2S还原引起GO表面吸附的Pb释放,实验条件下有19.9%—35.3%被吸附的Pb以离子形态释放出来.光谱分析表明,吸附Pb的GO在厌氧条件下被Na2S还原致使GO表面含氧官能团减少,造成Pb解吸附,解吸附释放出的部分Pb与反应体系中的硫化物结合生成PbS沉淀.附着Pb的GO进入还原环境后,以Pb^(2+)离子形式解吸附释放的Pb会引起水体的再污染.

Lead removal using high adsorption capacity graphene oxide （GO） has attracted increasing attention recently, whereas the potential release of Pb was GO into groundwater under the reduction environments is presently underappreciated. This research investigated the fate of Pb adsorption on GO surface in the presence of S2-, a typical metabolic product of sulfate reducing bacteria （SRB） in anaerobic environments, with batch experiments and XPS, FTIR, SERS and XRD speetroscopic analysis. The experiment results demonstrated the adsorption of Pb2＋ on GO before and after reduction by Na2 S can be fitted well by Langmuir model and the maximum adsorption capacity was 937.65 and 92.99 mg·g-1 respectively. 19.9%--35.3% of Pb was released from GO as Pb2＋ in the presence of N%S under anaerobic condition, and the PbS precipitates were confirmed by XRD. The main mechanism of Pb2＋ released from GO was the loss of carbonyl group on GO surface induced by N% S reduction. The mobilization of adsorbed Pb2＋ on GO surface will increase environmental risk especially in anoxic environment, such as groundwater, sediment-water interface and stratified water column.