REMOVAL OF LEAD FROM SOLUTION USING NONLIVING RESIDUAL BREWERY YEAST

A number of preparations of residual non-living brewery yeast were exa mined for their ability to remove lead from solution. Those preparatio ns included washed and un-washed intact yeast and washed and un-washed homogenates of the yeast cells. Using biosorption isotherm analysis i t was found that the washed and un-washed preparations of intact, non- living yeast exhibited maximum biosorption capacities for lead of 127 and 99 mg/g dry weight biomass, respectively. The washed and unwashed cell homogenates exhibited maximum biosorption capacities of 38 and 13 9 mg lead/g dry weight biomass, respectively. Since it had previously been shown that these preparations of biomass were capable of removing uranium from solution by combined biosorption and precipitation proce sses, it was decided to examine removal of lead from solution using a form of equilibrium dialysis in which the biomass was retained within a semi-permeable membrane during contact reactions. The results sugges t that precipitation plays an important role during removal of lead fr om solution, and this is partially due to membrane-permeable substance s released from the biomass into the membrane-excluded solution. The r esults demonstrate that removal of lead from solution by some of the y east preparations used in this study involves combined biosorption and precipitation.