Ion Exchangers in Radioactive Waste Management. Part VIII*: Radiotracer Studies on Adsorption of Strontium Ions on Hydrous Manganese Oxide

Abstract

Hydrous manganese oxide (HMO) is exploited as adsorbent for the decontamination study of strontium ions from aqueous radioactive waste solutions under simulated conditions using batch technique. The dependences of removal on various physicochemical conditions, such as contact time, concentration, temperature and pH of the adsorptive solution, were established using radiotracer technique. The results show that adsorption essentially reaches a plateau value in ca. 90 min, and the data thus obtained fit well into the classical Freundlich adsorption isotherm over a wide range of concentrations (IO -2 -IO -7 M). Lower desorption values, little affected by increase in temperature, show the process to be irreversible. The exposure of HMO to neutrons and "/-radiations from a 11.1 GBq neutron source up to certain periods results in a nominal change in sorption characteristics, indicating it be radiation-stable.

A Comparison of Strontium Sorption to Hydrous Aluminum, Iron, and Manganese Oxides

“…3), which is in good agreement with others (48,61). The pH pznpc of HMO is approximately 2.55 Ϯ 0.05, which lies in the range of pH 1.5 to 3.0 reported by others (14,23,62). The pH pznpc of ferrihydrite has been reported in the range 7.0 to 8.0 (11,48,60).…”

“…Adsorption edge studies were conducted at room temperature (ϳ25°C) and two ionic strengths (54). Isotherms were conducted at multiple temperatures (4°C Ն T Ն 25°C) and three pH values to evaluate enthalpy and the distribution mechanisms, respectively (23,35,(55)(56)(57). Activation energies, related to enthalpy through a proportionality constant (␣) based on the Polyani relationship (58), were used to calculate theoretical surface diffusivities.…”

“…Studies have been conducted in the past to assess the influence of important factors such as pH, ionic strength, temperature, and strontium concentration on the sorption of strontium ions to sediments (22)(23)(24)(25)(26)(27). In addition, Oscar and Humme (28) studied the effect of particle concentration and found that strontium sorption to bentonite particles decreased with increase in particle size; this effect was attributed to the particleparticle interactions or to blocking of some sorption sites.…”

“…In addition, Oscar and Humme (28) studied the effect of particle concentration and found that strontium sorption to bentonite particles decreased with increase in particle size; this effect was attributed to the particleparticle interactions or to blocking of some sorption sites. Most studies have been based on the assumption that strontium sorption reaches equilibrium very rapidly, within a few hours (22)(23)(24)(25)(26)(27)(28)(29). However, in natural systems sorption reactions can continue for days, months, or years (20, 30 -43).…”

Amorphous MnO2 –TiO2 Composites as Sorbents for Sr2+ and UO22+

“…Typical K d values for manganese oxides are ca. 100 mL/g (Kanungo, 1991;White and Labayru, 1991;Misra and Tiwary, 1995;Leontíeva, 1997). Like for other materials of high affinity to strontium, the dependence of adsorption of Sr 2+ on pH reaches a plateau in alkaline media (Misra and Tiwary, 1995).…”