凹凸棒石粘土吸附废水中污染物机理探讨

A Discussion on the Adsorption Mechanism of Palygorskite Clay to Pollutants in Wastewater

凹凸棒石是链层状硅酸盐 ,具有 0 .38nm× 0 .6 3nm的孔道。许多研究者据此都把凹凸棒石粘土吸附废水中污染物的机理解释为凹凸棒石具有微孔道和较大的比表面积 ,并且这一解释被普遍接受。作者根据凹凸棒石矿物晶体结构和吸附选择性以及吸附实验研究认为 ,由于凹凸棒石孔道直径小于大多数分子及水合离子的直径 ,除少数简单分子和离子外 ,多数分子和离子都不能进入凹凸棒石孔道 ,而且凹凸棒石内孔道选择性优先吸附水分子 ,因而在多数水处理中 ,凹凸棒石对吸附质的吸附不是内表面吸附 ,而是外表面吸附。并且这种外表面吸附属于凹凸棒石的胶体和离子交换吸附。除了溶液的 pH值等介质条件外 ,共存胶体蒙脱石和凹凸棒石的相互作用可能对凹凸棒石粘土的吸附性能起重要作用。

Palygorskite is a chain-layered silicate, with a aperture pass of 3.8 ×6.3A.It is gene? rally regarded that because this mineral has microapertur e pass and relatively larger specific surface area, the palygorskite clay is capable o f adsorbing the pollutants in wastewater. Based on the crystal structure of paly gorskite,its adsorption selectivity and our adsorption experiments, the present author holds the following opinion: because most molecules and hydrated ions hav e the diameters larger than that for the aperture pass of palygorskite, they u sually can not get into the aperture pass of palygorskite. Moreover, the inner ape rture pass of palygorskite preferentially adsorbs the water molecules. Terefore, in most cases during wastewater disposal processing the adsorption of palygorsk ite to pollutants is not an inner-surface adsorption, but an outer-surface ad sorption. This outer-surface adsorption is a kind of colloidal and ion exchange ad s orption. Besides the acidity of the solutions, the interaction of coexisting col loidal montmorillonite and palygorskite may play an important role in adsorption ability of palygorskite clay.