水悬浮体系中凹凸棒石与Cu^(2+)作用机理

Mechanism of Interaction between Palygorskite and Copper Ion in an Aqueous Suspended System

研究矿物吸附重金属性能和机理 ,对正确认识矿物吸附性质、环境矿物材料应用研究以及重金属环境化学行为具有重要理论和实际意义。凹凸棒石是重要粘土矿物之一 ,也是重要的环境矿物材料 ,其吸附净化功能潜在应用受到广泛关注。在制备凹凸棒石纯样基础上 ,进行了凹凸棒石吸附Cu2 + 单因素实验 ,吸附前后溶液pH值变化观测和吸附Cu2 + 后凹凸棒石表面结构高分辨透射电镜调查。结果表明 ,从表面来看 ,凹凸棒石对Cu2 + 的吸附性能主要受振荡速度、吸附时间、初始溶液pH值、吸附剂用量等因素影响 ,但实际上 ,凹凸棒石对Cu2 + 的吸附作用主要是凹凸棒石诱导的Cu2 + 水解沉淀作用以及凹凸棒石 (带负电荷 )与氢氧化铜 (带正电荷 )正负电荷胶体颗粒的互相作用 ,这有别于严格意义的矿物界面吸附作用。产生这种作用的机制在于凹凸棒石属于天然纳米矿物材料 ,具有较高的表面化学活性 ,凹凸棒石 -水悬浮体系中凹凸棒石表面水解呈现出碱性 ,结果导致吸附平衡水溶液pH值较初始水溶液有较大程度的升高 ,达到Cu2 + 水解基本完全的pH条件。

Investigating adsorption mechanism and ability of the heavy metal ions on minerals is important for correct understanding properties of mineral adsorption, application of environmental mineral materials, behavior of environmental chemistry of heavy metal ions. It is commonly accepted that palygorskite is an important environmental mineral material. On the basis of preparing pure palygorskite sample, experiments of copper ion adsorption on palygorskite were carried out under single effecting factor. Meanwhile, pH values of solution were tested and surface structure of palygorskite was investigated before and after adsorption experiments. The results indicate that mechanism of removing copper ion by palygorskite was mainly contributed to copper ion hydrolysis by palygorskite inducement and interaction between copper hydroxide (positive charge colloid) and palygorskite (negative charge colloid) although the removal efficients of copper ion is related to oscillating rate, adsorption time, initial pH value and amount of adsorbent. Strictly speaking, this mechanism is different from adsorption of mineral interface. Because palygorskite has nanometer crystals and is active in surface chemistry, its surface hydrolysis behaves alkaline in the aqueous suspended system of palygorskite-water. It leads the pH value of solution to be increased, at which the copper ion could be basically wholly hydrolysed.