沸石掺量对膨润土类衬垫重金属吸附特性的影响

Effect of zeolite content on the heavy metal adsorptionproperty of bentonite liners

膨润土衬垫作为垃圾填埋场防渗系统,遇重金属等有害物质时性能会下降。采用单元体试验分析Zn^(2+)对膨润土渗透特性的影响和沸石改善膨润土膨胀性能的效果。研究结果表明:沸石的掺入能改善膨润土的自由膨胀量,其中掺量为12.5%时效果最好;随着沸石掺量增加,混合土渗透性能得到提升,渗透系数从10^(-7) cm/s降至10^(-8 )cm/s;同一沸石掺量下,Zn^(2+)浓度上升,渗透性能下降;沸石掺入后膨润土膨胀量增大且紧密地附着在石屑表层,吸附渗滤液中离子,因此混合土拥有较强的吸附能力,渗滤液中Zn^(2+)浓度下降。研究成果对垃圾填埋场衬垫系统设计和应用具有较好借鉴意义。

Bentonite liners are used as a barrier system in a landfill.Their performance will degrade when exposed to heavy metals and other harmful substances.Unit cell tests are conducted to analyze the effect of Zn^(2+) on the permeability characteristics of bentonite and the improvement effect of zeolite on the swelling properties of bentonite.The research results show that the addition of zeolite can improve the free swelling index of bentonite and the best effect will be achieved for a content at 12.5%.With the increase of zeolite content,the permeability of mixed soil is improved and the permeability coefficient decreases from 10^(-7) cm/s to 10^(-8) cm/s.For a given zeolite content,the Zn^(2+) concentration increases but the permeability decreases.When zeolite is added,bentonite expands and adhere to the surface of stone filings,absorbing ions in leachate.Therefore,mixed soil has a stronger adsorption capacity and the Zn^(2+) content in leachate decreases.The research results can provide reference for the design and application of landfill liner systems.