Polymer modified biomass of baker's yeast for treating simulated wastewater containing nickel and lead

Baker's yeast was cross-linked by glutaraldehyde and then modified by grafting with poly(amic acid), which was prepared via reaction of pyromellitic dianhydride (PMDA) and arginine at 50 degrees C. The morphology of the pristine, cross-linked, and modified biomass was observed by microscope. The presence of poly(amic acid) on the biomass surface was verified by X-ray photoelectron spectroscopy (XPS) analyses. Due to the high density of the functional groups on the modified biomass surface, the metal adsorption capacity for nickel and lead increased significantly, especially when the carboxylic acid groups were converted into carboxylate ions using NaOH. The adsorption process for nickel and lead adsorption followed the pseudo-second-order kinetics. The metal adsorption data were fitted with the Langmuir and Freundlich isotherms with the former having a better fit. Using the Langmuir adsorption isotherm, the maximum uptakes for nickel and lead were found to be 0.848 and 0.980 mmol g(-1) respectively which were about 15 and 11 times higher than the prisitine biomass. In the simulated wastewater containing 0.400 mmol l(-1) of Ni2+ and Pb2+, the metal adsorption capacity of Ni2+ and Pb2+ reached 0.365 mmol l(-1) and 0.390 mmol l(-1). respectively. The metal ions loaded biomass was regenerated using Ethylene Diamine Tetraacetic Acid (EDTA) solution and used repeatedly over four cycles with little loss of uptake capacity. Copyright (c) 2007 John Wiley & Sons, Ltd.