Sorption and desorption of Co(II) on alumina: mechanisms and effect of humic substances

The effects of pH. ionic strength and humic substances on the sorption and desorption of Co(II) on alumina and silica were, respectively investigated by using radiotracer Co-60. The distribution coefficients, the breakthrough curves and the displacement curves were experimentally determined in the batch and the column experiments. The pH and the humic substances influenced the sorption of Co(II) on alumina greatly as compared with the sorption of Co(II) on silica. It was found that the sorption characteristics of Co(II) onto alumina and silica are distinctly different, that the strong chemical bonds are formed between the bare alumina surface and Co(II) and between the coated alumina surface and Co(II), and that a transition from the adsorption to the surface-induced precipitation of Co(II) on the bare alumina surface takes place. (C) 2002 Elsevier Science Ltd. All rights reserved.