Abstract

The adsorption‐desorption of copper ions and a mixture of five metal ions (cadmium, copper, nickel, lead and zinc) in aqueous solutions by a spruce sawdust column was reported. Different studies about the copper binding mechanism, the efficiency of some regenerating solutions for the copper desorption, the use of column for copper adsorption‐desorption by successive cycles as well as the adsorption‐desorption of a multi‐component solution were investigated. An ion exchange mechanism seemed to explain the removal of copper by the natural components of sawdust, i.e., calcium, magnesium and manganese accounting for 71, 13 and 5.5% respectively of the copper binding on sawdust. But, there was evidence variation in the contribution of these ions during the copper adsorption in the continuous flow process. Regeneration of the sawdust column was described by the efficiency sequence: H∗ > Ca²⁺ ≫ Na⁺, where protons were the most promising regenerating agents. Adsorption‐desorption cycles showed that copper binding capacity of sawdust, after a decrease of 23% between cycles 1 and 2, was stabilized at 3.1×10⁻² meq g⁻¹ for the following cycles. Adsorption of a mixture of five metal ions indicated that nickel broke through first when saturation of sawdust was reached, followed by the other metal ions in the order: zinc, cadmium, copper and lead. The effects of competitive ion exchange, because of affinity differences between the metal ions for sawdust, resulting in the metals having the lower affinity being displaced by those having a higher one and to overshoot the 0.2 meq l⁻¹ feed solution