Biosorption of nickel (Ni2+) and copper (Cu2+) by lyophilized Pseudomonas a
eruginosa cells was investigated based on Freundlich isotherm. Bacterial bi
omass 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 d
eposited 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 Na
OH, NH4OH or toluene enhanced the metal loading capacity, whereas, oven hea
ting (80 degrees C), autoclaving (120 degrees C, 15 lb (in.(2))(-1)), acid,
detergent and acetone treatments were inhibitory. In bimetallic combinatio
n, 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) w
as 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 reserve
d.