Sorption of nickel on marl

Batch sorption experiments using nickel have been carried out on marl, a sedimentary, carbonaceous rock. All experiments were performed with a synthetic water of pH 7.3 and in an atmosphere of N₂/1% CO₂. Over the equilibrium nickel concentration range of 10^–11–10^–5M, sorption was linear and reversible with R_d of 819 ml g^–1. Owing to the linear sorption behavior, R_d was independent of rock/water ratio (r/w=1/5–1/100). The data suggested that at Ni] lower than 10^–7M an isotope exchange mechanism operated, whereas at higher Ni], sorption involved ion exchange. Sorption experiments on some of the components of marl indicated that nickel adsorbs mainly on the clay minerals and on the trace of iron hydroxide present; sorption on calcite and quartz was low.