Sorption and desorption characteristics of cobalt in clay: Effect of humic acids

Abstract

The effect of humic acid (HA) on the sorption and desorption of Co(II) on kaolin was investigated. Cobalt ions interact with carboxylic and phenolic groups in HA and form HA-cobalt complex. The solubility of HA was affected by the surrounding pH. The presence of HA reduced the equilibrium time for the Co(II) sorption on kaolin compared to the absence of HA. Solution pH, not HA concentration, was a main factor to affect sorption of Co(II) on kaolin in the presence of HA. In the kinetic sorption and desorption of CO(II) on kaolin, the presence of HA shortened the breakthrough of CO(II) sorption on kaolin compared to bare kaolin, and HA solution enhanced the displacement of Co(II) from kaolin compared with deionized water.