场地土壤中有效态砷的稳定化处理及机理研究

分别以生石灰和亚铁盐作为辅助剂与稳定剂对2种砷污染的土壤进行稳定化处理,通过化学浸出、形态及结构研究,揭示土壤中有效砷的稳定效率和机理.结果表明,外源铁添加量与土壤砷含量(Fe/As)的物质的量比达到6:1~8:1,CaO投加比例为0.05%~0.1%(w/w)时,土壤中有效态砷的稳定效率超过85%.土壤有效砷的稳定化处理主要是将砷从非专性吸附态和专性吸附态转化为弱结晶的铁铝或铁锰水化氧化物结合态、结晶铁铝或铁锰水化氧化物结合态.稳定处理后2种污染土均有新物相羟砷铜矿(As2Cu5H4O12)生成.

Stabilization treatment of available arsenic in contaminated soils and mechanism studies

Lime and Ferrous salt was used as the auxiliary agent and stabilizing agent to treat two arsenic contaminated soils. Following chemical leaching test, the stabilizing effectiveness and mechanism of available arsenic on treated soil were shown using morphology and structure analysis. Importantly, the stabilizing efficiency of arsenic for the two types of soils were both over 85% when the ratio of exogenous Fe and soil As (mol/mol) was 6:1~8:1 and the dosing ratio of CaO was 0.05% ~ 0.1% (w/w). The stabilization of arsenic in soil was attributed mainly to two following reasons: (1) arsenic was transformed from non-specific adsorption and the specific adsorption state into the weakly crystalline Fe-Al or Fe-Mn hydrated oxides and (2) crystalline Fe-Al or Fe-Mn hydrated oxides state. The new phase of hydroxyl arsenic copper mineral (As2Cu5H4O12) was generated after the stabilization treatment of the contaminated soils.