Competitive adsorption of Pb²⁺ and Cd²⁺ onto activated carbon produced from municipal organic solid waste

Competitive adsorption of cadmium (Cd²⁺) and lead (Pb²⁺) was investigated using activated carbon (AC) produced from municipal organic solid waste. The effect of pH, contact time, metal concentration and adsorbent dosage on the performance of the adsorption process was investigated using synthetic binary metal solutions. The results showed that optimum removal efficiency of both metals from binary metal solutions could be achieved at a pH value of 5 and a contact time of 120 min. Moreover, the results showed that, for both metal ions, the increase in the initial metal concentration led to an increase in adsorption capacities and decrease in removal efficiencies. At a Cd²⁺ concentration of 100 mg/L, the removal efficiency of Cd²⁺ was found to decrease from 21.42% to 6.79% (68.3% decrease), when Pb²⁺ concentration was increased from 25 to 300 mg/L, respectively. On the other hand, the increase in the AC dosage was found to result in decreasing the adsorption capacity from 19.65 to 10 mg/g and from 61 to 12 mg/g when AC dosages were increased from 25 to 400 mg, for Cd²⁺ and Pb²⁺, respectively. The experimental results of both metals were found to fit non-linear Freundlich adsorption isotherm and pseudo-second-order kinetic models.