REMOVAL OF NICKEL IONS FROM AQUEOUS-SOLUTION BY BIOMASS AND SILICA-IMMOBILIZED BIOMASS OF MEDICAGO-SATIVA (ALFALFA)

The characteristics of the roots and shoots from seven different popul ations of Medicago sativa (alfalfa) were examined for their ability to bind nickel ions from aqueous solution. Batch laboratory experiments were performed to determine the optimal pH for nickel binding to the a lfalfa plant tissues which was between pH 5 and 6. From these experime nts, pH profiles were performed to gain information about the chemical functional groups in the alfalfa plant tissues responsible for the ni ckel binding, Binding time dependency studies determined that approxim ately 80% of the nickel ions bound to the alfalfa plant tissues in les s than 5 min. Binding capacity experiments showed that nickel binding was as much as 4.1 mg of nickel per gram of alfalfa biomass. Nickel re covery experiments showed that more than 90% of the bound nickel was r emoved from the alfalfa biomass, Column experiments were conducted to examine the binding of nickel to silica immobilized alfalfa plant tiss ues under flow conditions. Results From these experiments showed that more than 90% of the retained nickel was recovered after four bed volu mes of 0.1 M HCl solution were passed through the column. After 12 cyc les on the same column, the efficiency for nickel removal and recovery from solution was stable.