226Ra, 238U and Cd adsorption kinetics and binding capacity of two cyanobacterial strains isolated from highly radioactive springs and optimal conditions for maximal removal effects in contaminated water

Biomass-based decontamination methods are among the most interesting water treatment techniques. In this study, 2 cyanobacterial strains, Nostoc punctiforme A.S/S4 and Chroococcidiopsis thermalis S.M/S9, isolated from hot springs containing high concentrations of radium (Ra-226), were studied to be associated with removal of radionuclides (U-238 and Ra-226) and heavy metal cadmium (Cd) from aqueous solutions. The adsorption equilibrium data was described by Langmuir and Freundlich isotherm models. Kinetic studies indicated that the sorption of 3 metals followed pseudo-second-order kinetics. Effects of biomass concentration, pH, contact time, and initial metal concentration on adsorption were also investigated. Fourier-transform infrared spectroscopy revealed active binding sites on the cyanobacterial biomass. The obtained maximum biosorption capacities were 630 mg g(-1) and 37 kBq g(-1) for U-238 and Ra-226 for N. punctiforme and 730 mg g(-1) and 55 kBq g(-1) for C. thermalis. These 2 strains showed maximum binding capacity 160 and 225 mg g(-1), respectively for Cd adsorption. These results suggest that radioactivity resistant cyanobacteria could be employed as an efficient adsorbent for decontamination of multi-component, radioactive and industrial wastewater.