Adsorption of copper and zinc by oil shale

Oil shale is able to remove appreciable amounts of copper and zinc ions from aqueous solutions. It was noted that an increase in the adsorbent concentration with constant copper or zinc concentration resulted in greater metal removal from solution. An increase in the copper or zinc concentration with a constant sorbent concentration resulted in higher metal loading per unit weight of sorbent. For both metals, copper and zinc, equilibrium was attained after 24-h contact time. Increase in the initial pH or temperature of the metal solution resulted in an increase in the metal uptake per unit weight of the sorbent. Freundlich isotherm model was found to be applicable for the experimental data of Cu²⁺ and Zn²⁺. The results showed that oil shale could be used for the adsorption of the Cu²⁺ and Zn²⁺ with higher affinity toward Zn²⁺ ions. Addition of sodium salt to the metal solution influenced copper removal positively, but inhibited zinc removal.