Metal adsorption and desorption by lyophilized Pseudomonas aeruginosa

Biosorption of nickel (Ni2+) and copper (Cu2+) by lyophilized Pseudomonas aeruginosa cells was investigated based on Freundlich isotherm. Bacterial biomass showed significant sorption of both Ni (265 mg g(-1)) or Cu (137.6 mg g(-1)), and was also superior over the cation exchanger, IRA 400 (98 mg Ni g(-1) or 26.5 mg Cu g(-1)). Metal binding by the test organism was a fast saturating, pH-dependent process. The optimum pH for Cu adsorption was 7.0 and for Ni 8.0. X-ray diffraction studies revealed that both cations were deposited on the cell predominantly as phosphide crystals. The participation of carboxyl, carbonyl, and phosphoryl groups along with H-bonding in metal sorption was evident in IR spectra. Biomass pretreatment by agents like NaOH, NH4OH or toluene enhanced the metal loading capacity, whereas, oven heating (80 degrees C), autoclaving (120 degrees C, 15 lb (in.(2))(-1)), acid, detergent and acetone treatments were inhibitory. In bimetallic combination, Na, K or Ca increased sorption of Ni as well as Cu in contrast to Cd or Pb. Mineral acids (HCl, H2SO4 and HNO3) and NTA could recover more than 75% (on average) Ni or Cu adsorbed on the biomass. Calcium carbonate (10 mM) was efficient in Ni desorption (71%) compared to Cu (57%). Noticeably sodium carbonate remained specific for Cu remobilization (88%) than Ni (21%). The data are in favour of deployment of the test biomass as an efficient metal removal/recovery system. (C) 1999 Elsevier Science Ltd. All rights reserved.