Cadmium(II) and Lead(II) removal by Chlorella sp. Immobilized and E. coli genetically engineered with mice Metallothione
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Cadmium(II) and Lead(II) removal by Chlorella sp. Immobilized and E. coli genetically engineered with mice Metallothionein I V. Almaguer-Cantú1, L. Morales-Ramos1, K. Arevalo-Niño1, M.T. Garza-González2, I. Balderas-Rentería2 1 Intituto de Biotecnología, FCB, UANL, Ave. Barragán s/n, Cd. Universitaria, C.P. 66451 San Nicolás de los Garza, N.L., México. 2 Escuela de Posgrado, FCQ, UANL, Ave Guerrero s/n, Col Treviño, Monterrey, N.L., México.
ABSTRACT The pollution caused by heavy metals is one of the major environmental problems that is imperative to be solved. New technologies, easy to implement and to adapt to any system, deserve special attention and are a focus of this work the ability of Chlorella sp. and E. coli genetically engineered with mice metallothionein I, both immobilized in alginate of calcium to remove Cd(II) and Pb(II) from aqueous solutions was investigated in batch assays for the treatment of diluted aqueous solutions. The kinetics, sorption capacities and sorption percentage were determined. The influence of metal concentration in solution is discussed in the terms of Langmuir isotherm and constants. Sorption capacities increased with increasing metal concentration in solution. For solution containing 300 mg/L of metal, the observed uptake capacities were 94.9411.094 mgCd/gChlorella., 24.0762.292 mgCd/gE.coli and 239.172.478 mgPb/gChlorella, 37.9524.245 mgPb/gE.coli. The Langmuir constants to Chlorella sp. were qmax=285.72(mgPb/g), b=0.0276(l/mgPb), qmax=103.65(mgCd/g) and b=0.0005(l/mgCd) while to E. coli were qmax=28.141(mgPb/g), b=0.113(l/mgPb), qmax=24.272(mgCd/g) and b =0.019(l/mgCd). The biomass of the algae showed to have better capacity of metallic sorption that the biomass of the bacteria genetically engineering. The study proved that microorganisms biomass is a suitable material for the removal of the studied heavy metals ions from aqueous solutions, achieving removal efficiencies higher than 90%, and could be considered as a potential material for treating effluent polluted with Cd(II) and Pb(II) ions. INTRODUCTION The metal contamination of the environment reflects both natural sources and the contribution from industrial activity [1-2]. The heavy metals such as lead and cadmium are elements that occur naturally in the earth´s crust. It is highly toxic elements which, in humans, can cause serious damage to the kidneys and bones, and is probably best known for its association with important disease [3]. Biological materials can remove metals, compounds and particulates from solution with a process called biosorption. Both living and dead biomass can be used for metal removal. Biological materials such as bacteria [4], algae [5], and yeast [6] are known to accumulate metals from aqueous solutions. The cells walls of these microorganisms include a large number of complex organic compounds and their polymers, such as cellulose, xylans, pectin, chitin, chitosan, proteins, and lipids. Such compounds contain many functional groups, including carboxylate, hydroxide, amine, imidazole, sulfa
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