ADSORPTION OF HEAVY-METALS BY GREEN-ALGAE AND GROUND RICE HULLS

This research demonstrates the applicability of low cost, readily available alternate adsorbents to remove and recover toxic heavy metals from water, Heavy metal ion adsorption has been investigated using two different adsorbing biomasses, algae and rice hulls. Algal biomass adsorption studies were conducted with : As, Cd, Co, Cr, Pb, Ni and Zn, and rice hull biomass adsorption studies were conducted with: As, Cd, Cr, Pb and Sr. Both biomasses were dried and pulverized to maximize surface area. The green alga, Chlorella minutissima, adsorbed greater than 90% of the initial Pb, and greater than 98% of the initial Co concentrations. Rice hulls (Mars and Rico Varieties) exhibited similar adsorption percentages: 94% for Sr, and greater than 99% for Pb. The rate of adsorption was fast; the solution metal concentration reached equilibrium within minutes. The cell wall metal complex was found to be stable; the bound metal did not desorb over time under static conditions. Most cationic metal ions could be recovered from the biomass through desorption by lowering the pH of the medium.