溶液介质条件对重金属离子与石英表面反应的影响

Influences of aqueous medium conditions on surface reactions of heavy metal ions with quartz

实验研究表明，随着溶液pH值的升高，石英对Cu2+、Pb2+和Cd2+等重金属离子的吸附量和表面吸附覆盖率逐渐增大，而表面反应产物的结合形态相应地出现由单核化合物、多核化合物[SOCu4(OH)4+3]，直至表面沉淀[SOH…Cu（OH）2(S)]。随着温度升高，石英对Cu2+、Pb2+和Cd2+等重金属离子的吸附量逐渐减小。而随着溶液离子强度的增大，石英对Cu2+离子的吸附量和表面离子覆盖率也逐渐减小。可见，溶液pH值等介质条件对石英表面反应具有很大的影响，甚至可导致金属离子与石英表面反应机理与模式的改变，即由吸附反应向表面沉淀变化。

Sorption of divalent metal ions, including Cu2+, Pb2+ and Cd2+, onto quartz was measured at the same initial concentration of the ions and ionic strength (I= 0. 1 mol/L) under condition of pH value ranging from 2. 6 to 11. The sorption densities and surface coverage of the ions increased with increasing solution pH value. The experimental measurements can be simulated with mechanisms to form mononuclear complexes under conditions of low pH (< 6. 5 for Cu2+; < 7. 0 for Pb2+ and Cd2+), and to form multinuclear complexes versus three-dimensional precipitates under conditions of high pH (> 6. 5 for Cu2+; > 7.0 for Pb2+ and Cd2+ ). The sorption densities of the ions increased with a rise in temperature. The sorption densities of Cu2+ increased with the ionic strength that change from 0.1 to 1. 0 mol/L, while it was opposite in the case for Pb2+ and Zn2+ ions. Therefore, surface reactions of the heavy metal ions with quartz can be influenced by the factors of pH value, temperature and ionic strength.