COBALT, COPPER, AND MANGANESE ADSORPTION BY ALUMINUM AND IRON-OXIDES AND HUMIC-ACID

Adsorption of cobalt (Co), copper (Cu), and manganese (Mn) by synthetic aluminium oxide, ferrihydrite, goethite, extracted humic acid, and a sandy soil sample were determined as a function of metals concentration (0-1.2 mM) and pH (3.8-8.2). For each pH and adsorbent, the Langmuir adsorption maximum (adsorption capacity) was calculated. The position of the adsorption curves for Co, Cu, and Mn as a function of pH has been shown to be related to the first hydrolysis constant of the cations in solution (pK1). The sequence of preference of the three metals to the studied adsorbents decreased in order Cu >> Co > Mn. The results obtained from this study showed that the Co, Cu, and Mn adsorption characteristics of soils are probably controlled to large extent by their organic matter and oxides contents.