Metal cations adsorption by an authentic brazilian variable charge soil

摘要

Adsorption of Cd, Cu, Ni and Zn on surface and subsoil samples from a typical Brazilian variable charge soil was investigated over the pH range from 3 to 8 using two quantitative adsorption parameters: pH50 and proton coefficient (α). A sharp increase of ad sorption density was observed within a very narrow pH range, usually less than two pH units (adsorption edge). The variation in the pH50 values indicated that the identity of the adsorbing ion was a critical factor determining the pH range over which adsorption occurs. As the smaller the pH50, the more selective the adsorbent for the metal and the following affinity sequence was