Isotherm studies for the determination of Cd(II) ions removal capacity in living biomass of a microalga with high tolerance to cadmium toxicity.

Abstract

The biosorption characteristics of Cd(II) ions using the living biomass of the marine diatom Phaeodactylum tricornutum were investigated. This microalga is a highly tolerant species to cadmium toxicity, for this reason is interesting to know its potential for use in the removal of Cd(II) ions. The use of living biomass offers better possibilities than dead biomass since cadmium can also be bioaccumulated inside the cells. For this purpose, tolerant species are necessary. P. tricornutum is within this category and in the present manuscript is demonstrated that this microalga has a very good potential for bioremediation of Cd(II) ions. Cadmium removed by the cells was divided into three fractions: total, intracellular and bioadsorbed. The experiments were conducted for 96 h in a concentration range of 1-100 mg Cd(II)/L. Each fraction was characterized every 24 h by sorption isotherms. The experimental isotherm data were analysed using the Langmuir, Freundlinch, Dubinin-Radushkevich and Temkin equations. The biosorption was well described by Langmuir isotherm followed by Freundlich. The worst model was Temkin. The biosorption capacity of this microalga for Cd(II) ions was found to be 67.140 ± 3.247 mg/g after 96 h with approximately 40% of this capacity in the intracellular fraction. The bioconcentration factor determined was 2204.7 after 96 h and with an initial Cd(II) concentration of 1 mg/L.