ABILITY OF SILICA-IMMOBILIZED MEDICAGO-SATIVA (ALFALFA) TO REMOVE COPPER IONS FROM SOLUTION

Preliminary screening laboratory batch experiments to determine the bi nding ability of seven different populations of Medicago sativa (alfal fa) showed good copper binding characteristics of the biomasses studie d. All seven populations examined had similar trends for binding coppe r as a function of pH. The copper binding by the different alfalfa pop ulations occurred within 5 min. All the alfalfa biomasses showed high copper binding, but the capacities varied according to the alfalfa sam ple studied. The pH dependence of the copper ion binding to the alfalf a biomasses suggested that it might be possible to recycle the system much like an ion-exchange resin. However, the alfalfa cells cannot be packed into a column because the cells clump together and restrict the flow. We immobilized the cells of Malone alfalfa shoots in a silica m atrix. Column experiments for copper binding by the silica immobilized alfalfa demonstrated that the alfalfa tissues were capable of removin g considerable amounts of copper ions under flow conditions. After eve ry copper binding cycle most of the copper was desorbed with a few bed volumes of 0.1 M HCl. Our work indicates that the Malone-silica prepa rations are highly durable. We subjected the biomaterial to as many as 10 cycles of binding and elution without observing any significant de crease in copper binding capacity.