Biosorption Column Performance with a Metal Mixture

Abstract

The biosorption of Cu, Cd, and Zn from multicomponent mixtures was studied in equilibrium systems and in a flow-through column packed with potassium-saturated Sargassum algal biosorbent. Pretreatment of the biomass with calcium-, sodium-, magnesium-, and potassium-hydroxides was examined. KOH washing resulted in a stable biosorbent with an improved affinity for Zinc. Two-metal sorption resulted in Zn breaking through the column faster than Cd due to its low affinity. The sharp favorable Zn breakthrough curve can be explained by its affinity toward the biomass which is higher than that of K. An overshoot of the Zn exit concentration was observed and explained by the ion exchange between Cd and Zn, whereby the higher-affinity Cd from the solution displaces Zn already bound to the biosorbent. The same effect was observed for Zn, and to a lesser extent Cd, in three-metal sorption (Zn, Cd, Cu). The Cd exit concentration also exceeded its feed level as Cu displaced it on the binding sites of the biomass in the ...