Removal of Cadmium from Aqueous Solution Using Dried Biomass of <i>Euglena gracilis</i> var. <i>bacillaris</i>

The aim of this work was to evaluate the possibility of applying the dried biomass of <i>E. gracilis</i> var. <i>bacillaris</i> as a biosorbent for the removal of Cd. Experiments were carried out under conditions of batch systems involving aqueous solutions labelled with ¹⁰⁹CdCl₂. From the kinetics of Cd biosorption, it can be assumed that the Cd removal was a rapid process that achieved the concentration equilibrium of [Cd]_biomass:[Cd]_solution in the first minutes of the interaction. In individual experiments, the effect of solution pH, initial biosorbent, or Cd concentration was evaluated. According to MINEQL+ speciation modelling, it was found that the biosorption of Cd decreased linearly corresponding to a decrease in the proportion of Cd²⁺ in the solution. The biosorption data were well fitted to the Langmuir model of adsorption isotherm in comparison with the Freundlich model. The maximum biosorption capacity of the dried biomass of <i>E. gracilis</i> var. <i>bacillaris</i> for the removal of Cd was predicted and reached the value <i>Q_max</i> = 0.13 mmol/g or 14.1 mg/g (d.w.), respectively.