The sorption of cobalt by manganese minerals in soils

Abstract

Measurements were made of the sorption of copper, cobalt, and nickel by finely ground manganese nodules obtained from soil samples and it was found that very large amounts of these elements were sorbed by the manganese minerals in the nodules. The initial sorption of copper was greater than that of cobalt or nickel, but extraction of the sorbed elements with acetic acid showed that, once sorbed, cobalt was the most strongly held. Weight for weight, the manganese minerals sorbed, on the average, 6 times as much copper and 20 times as much cobalt as the associated soil materials. The corresponding ratios for the non-extractable fractions were 4 for copper and 160 for cobalt. The non-extractable fraction of the cobalt further increased on aging of the mineral after sorption, but little increase was observed for copper or nickel. These results explain the high concentration of cobalt found in manganiferous materials in soils.