Study of Simultaneous Radionuclide Sorption by Mixture Design Methodology

Assessment of modified Salvadora Persica for removal of 134Cs and 152+154Eu radionuclides from aqueous solution

Biosorption is a simple and economical method utilized to remove hazardous elements from a waste solution. In this study, a low-cost agricultural waste, Salvadora Persica, was modified with iron oxyhydroxide and evaluated as an economic biosorbent to remove cesium and europium radionuclides from their aqueous solutions. The modified biosorbent was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), elemental analysis as well as thermogravmetirc analysis (TGA). The sorption of ¹³⁴Cs and ^152+154Eu radioisotopes was investigated singly in a batch mode as a function of the solution pH, contact time, and the initial concentrations of the studied ions. The kinetic of the removal process was examined and it was found that the reaction obeys a pseudo-first-order model and the intraparticle diffusion is not the sole mechanism dominating the reaction. Temkin and Sips isotherm models provide the best fit for the equilibrium data. In addition, the sorption of cesium and europium ions was a spontaneous and endothermic process as inferred from thermodynamic studies. The reusability for the sorption of cesium and europium ions reveals the feasibility and efficacy of the modified biosorbent.

Evaluation of hydroxyapatite/poly(acrylamide-acrylic acid) for sorptive removal of strontium ions from aqueous solution

A composite polymer, hydroxyapatite/poly(acrylamide-acrylic acid), was synthesized by gamma-induced polymerization. The factors affecting the sorption process were evaluated. The removal increased with time and achieved equilibrium after 1 h for all initial concentration ranges (10-50 mg/L). The highest removal of Sr(II) was achieved using 50 mg/L at pH 6. The sorption process was found to follow a pseudo-first-order mechanism. The equilibrium data are best described by the Langmuir model, with a monolayer capacity of 53.59 mg/g. The values of thermodynamic parameters indicate that the sorption process is endothermic (ΔH > 0), increases randomness (ΔS > 0) and is spontaneous (ΔG < 0). The results imply that the composite could be used as a promising low-cost material for the removal of radionuclides from radioactive waste.

Sorbent materials for rapid remediation of wash water during radiological event relief

Procedures for removing harmful radiation from interior and exterior surfaces of homes and businesses after a nuclear or radiological disaster may generate large volumes of radiologically contaminated waste water. Rather than releasing this waste water to potentially contaminate surrounding areas, it is preferable to treat it onsite. Retention barrels are a viable option because of their simplicity in preparation and availability of possible sorbent materials. This study investigated the use of aluminosilicate clay minerals as sorbent materials to retain (137)Cs, (85)Sr, and (152)Eu. Vermiculite strongly retained (137)Cs, though other radionuclides displayed diminished affinity for the surface. Montmorillonite exhibited increased affinity to sorb (85)Sr and (152)Eu in the presence of higher concentrations of (137)Cs. To simulate flow within retention barrels, vermiculite was mixed with sand and used in small-scale column experiments. The GoldSim contaminate fate module was used to model breakthrough and assess the feasibility of using clay minerals as sorbent materials in retention barrels. The modeled radionuclide breakthrough profiles suggest that vermiculite-sand and montmorillonite-sand filled barrels could be used for treatment of contaminated water generated from field operations.