Multimetal biosorption in a column using Sargassum biomass

Removal of Cu, Cd and Zn from multicomponent mixtures by biosorption was studied in equilibrium biosorption systems and in a flow-through column packed with Sargassum algal biosorbent pre-saturated with potassium. The elution order of Zn, Cd and Cu from the column and their concentration overshoots at the column exit, were due to the differing affinities to the biosorbent. Low-affinity Zn broke through the column faster than Cd with a sharp favorable breakthrough curve due to the pretreatment of the biomass with K which features the lowest affinity of all the ionic species examined. K-form biomass gives the most effective utilization of the column bed. An overshoot of the Zn exit concentration was observed and explained by the sequential ion exchange between Cd and Zn during the operation of the column bed. The same effect was observed for both Zn and Cd when Cu was present in the feed solution. sorbing onto K-Sargassum biomass. A sharp Zn exit concentration overshoot was followed by the one of Cd that lasted until the later breakthrough of Cu was complete. In this system, the overshoot of Zn was caused mainly by its exchange for Cd ions in the biosorbent. While the Zn and Cd exit concentrations overshoots were close together, the time interval between Zn and Cu breakthroughs was much longer. This behavior is all based on the magnitude of relative affinities of Zn, Cd and Cu for the K-biomass determined from batch equilibrium experiments. The relative affinity coefficients were: K-Zn/K= 1.96, K-Cd/K= 3.70 and K-Cu/K= 16.51.