Radium removal from aqueous solutions by adsorption on non-treated and chemically modified biomass by-product

The adsorption efficiency of a biomass by-product (olive cake) regarding the removal of radium (²²⁶Ra) from aqueous solutions has been investigated prior and after its chemical treatment. The chemical treatment of the biomass by-product included phosphorylation and MnO₂-coating. The separation/removal efficiency has been studied as a function of pH, salinity (NaCl) and calcium ion concentration (Ca²⁺) in solution. Evaluation of the experimental data shows clearly that the phosphorylated biomass by-product presents the highest adsorption capacity and efficiency followed by the MnO₂-coated material and the non-treated biomass by-product. However, regarding the effect of salinity and the presence of competitive cations (e.g. Ca²⁺) on the adsorption/removal efficiency, the MnO₂-coated material shows the lowest decline in efficiency (only 2 % of the relative adsorption efficiency) followed by the non-treated and the phosphorylated biomass by-product. The results of the present study indicate that depending on the physicochemical characteristics of the radium-contaminated water, all three types of the biomass by-product could be effectively used for the treatment of radium-contaminated waters. Nevertheless, the MnO₂-coated material is expected to be the most effective adsorbent and an alternative to MnO₂ resins for the treatment of environmentally relevant waters.