Cr^(Ⅵ) adsorption on four typical soil colloids: equilibrium and kinetics

摘要

It is observed that the adsorption of chromium are greater on kaolinite minerals, red soil (R) and laterite (L) colloids than that on montmorillonite, indicotic black (IB) and yellow brown (YB) soil colloids. The adsorption process of Cr Ⅵ on these media can be further described by Langmuir or Freundlich equation quite well. The adsorption reaction of Cr Ⅵ is fast, and the adsorption equilibrium can be reached within the first two hours in moderate temperature. The adsorption quantity of Cr Ⅵ to kaolinite mineral increased with the increasing pH in the range of 2.0 to 7.0, then decreased at higher pH. But it showed some consistence among the four soil colloids. The lower the pH, the stronger the adsorption. The possible mechanisms are further discussed here. Meanwhile the influence of temperature on Cr Ⅵ adsorption on different soil colloid and clay minerals are also investigated.