钙矾石对Pb,Zn,Cd的化学俘获

Research on Chemical Entrapment of Pb,Zn,Cd by Ettringite

研究了钙矾石对Pb2+,Zn2+,Cd2+化学俘获的条件以及俘获量.钙矾石人工合成的试验发现,当液相中缺乏SO42-时,PbO22-,ZnO22-不能替代SO42-并与Ca2+,A lO2-等组分结合形成钙矾石;而当合成液中有SO42-时,Ca2+,A lO2-,SO42-在结合形成钙矾石的过程中能把Pb,Zn,Cd俘获到晶格中去.X射线衍射分析显示,钙矾石在俘获了Pb(Ⅱ),Zn(Ⅱ),Cd(Ⅱ)后个别衍射峰的峰强大增.对合成物进行化学组分测定发现,钙矾石对这3种元素俘获程度的排序为:Cd>Zn>Pb,而这个顺序也是这3种离子与Ca2+相似程度的排序,因此它们进入钙矾石晶格的途径很可能是以替换钙矾石中的Ca2+得以实现的.

The research aims to discover the conditions under which Pb^2＋, Zn^2＋ , Cd^2＋ can be chemically entrapped by ettringite and the amount of entrapments. The ettringites＇synthesis experiments indicate that PbO2^2- or ZnO2^2- can＇t enter ettringites＇ lattice as the replacement of sulfate when the solution is free of sulfate. When sulfate is present, the ettringites can form and partially accommodate Pb, Zn, Cd in the crystal lattice during their formation, thus giving rise to chemical entrapment. X-ray analysis shows that the intensity of some diffraction peaks increases a lot after ettringites accomodate these heavy metals. Chemical analysis of heavy - metalcontaining ettringites indicates that the amount of Pb, Zn, Cd entrapped by ettringites is in the order of Cd 〉 Zn 〉 Pb. However, the similarity between Pb^2＋, Zn^2＋ , Cd^2＋and Ca^2＋ is in the same order, suggesting that Pb^2＋ Zn^2＋ , Cd^2＋ enter ettringite lattice probably by the replacement of Ca^2＋ in ettringite.