Comparative biosorption of lead (II) using Saccharomyces cerevisiae and nanocarbon-alginate beads

Pb (II) removal from aqueous solution was studied with two immobilized sorbents, Saccharomyces cerevisiae-alginate beads and nanocarbon-alginate beads (nanocarbon is multi-walled carbon nanotube, MWCNT). Beads containing 0.6 or 0.8 g of sorbent were contacted with Pb (II) solutions at nominal concentrations of 50, 100, 300, and 500 mg/L (AAS-measured 58.1, 102.8, 323.0, and 496.0 mg/L). Yeast-alginate beads were more effective in dilute solution, with 37.65% removal within 5 min at 50 mg/L (0.8 g loading). The 0.8 g nanocarbon beads showed the highest apparent capacity at 500 mg/L (45.76 mg/g), since uptake had not plateaued by 60 min. The pseudo-second-order model described the kinetic data better than the pseudo-first-order model in 8 of 12 nonlinear fits, consistent with but not indicative of a chemisorption-limited rate step. The 500 mg/L data were excluded from modeling because the fits were poor or physically uninterpretable. From 50 to 300 mg/L, nonlinear fitting favored the Langmuir model for 0.6 g yeast and 0.8 g carbon and the Freundlich model for 0.8 g yeast and 0.6 g carbon, so the expected shift with loading appeared for yeast only. Yeast-alginate beads suit dilute Pb (II) streams and nanocarbonalginate beads suit concentrated streams.