Removal of radionuclide Sr2+ ions from aqueous solution using synthesized magnetic chitosan beads

Treatment of radioactive wastewater using direct contact membrane distillation

Direct contact membrane distillation (DCMD) was used to treat low level radioactive wastewater (LLRW). The dusty gas model (DGM) was used to analyze the mass transfer mechanism and calculate the permeate flux. The operating parameters such as feed temperature, feed velocity and feed concentration were studied. The experimental results showed that DCMD process can separate almost all Cs(+), Sr(2+) and Co(2+) from wastewater. The permeate flux decreased linearly when NaNO3 concentration increased from 1.0 to 200 g/L. The permeate flux remained about 60% of its initial flux even when NaNO3 concentration in feed solution was as high as 200 g/L. The dusty gas model can be successfully applied to estimate the mass transfer, and the experimental permeate flux values fitted well with that calculated by DGM. DCMD is a promising separation process for low level radioactive wastewater treatment.

Kinetics and thermodynamics of Cu(II) biosorption on to a novel magnetic chitosan composite bead

Novel chitosan/Fe3O4 composite beads were prepared and used for the removal of Cu(II) ions from aqueous solution. The effect of initial pH, metal ion concentration and temperature on the sorption capacity of the composite was investigated. The kinetics and isotherms of Cu(II) sorption were analysed by the intra-particle diffusion model and the Langmuir, Freundlich and Slips models, respectively. The results showed that diffusion was the rate-limiting step during the whole sorption process. The maximum sorption capacity of the composite chitosan was 121.9 mg/g beads (192.6 mg/g chitosan) at pH 5.0, and the sorption capacity increased with increasing temperature, indicating that the sorption process was endothermic. Thermodynamic parameters such as Gibbs free energy change (deltaG0), enthalpy change (deltaH0) and entropy change (deltaS0) were also determined. Desorption of the metal ions from the composite chitosan beads was achieved by using 0.05 M EDTA.