Hollow fiber supported liquid membrane studies using a process compatible solvent containing calix[4]arene-mono-crown-6 for the recovery of radio-cesium from nuclear waste

• A calix[4]arene-mono-crown-6 (CMC) ligand was used for Cs recovery.
• The solvent contained CMC in 60% dodecane + 40% iso-decanol.
• Solvent extraction, flat sheet and hollow fiber SLM studies carried out.
• Possibility of extraction of Cs(I) from HLW was explored.
• Diffusional parameters were also calculated.

Bis-octyloxy-calix[4]arene-mono-crown-6 (CMC) was evaluated for radio-cesium separation from acidic feed solutions using hollow fiber supported liquid membrane (HFSLM) technique. Solvent extraction and flat sheet supported liquid membrane (FSSLM) studies were pursued to optimize the conditions required for the subsequent HFSLM studies. The permeation rate of cesium in HFSLM increased steadily with nitric acid concentration from 1 M HNO3 to 6 M HNO3. At a moderate acidity of 4 M HNO3, which is the acid concentration of the high level waste, near quantitative (>99%) transport of cesium was possible within 2 h of operation at 300 mL scale. Transport was suppressed under simulated high level waste conditions due to the presence of large concentrations of cesium (0.32 g/L), but >90% transport was observed in 6 h. Stability of the membrane was excellent as monitored from 12 days of continuous operation. The permeability coefficient, mass transfer coefficient and various diffusional parameters of the diffusing metal/ligand species were calculated to understand the permeation behvaiour of cesium. The present work explored the possible use of CMC in hollow fiber contactor for radioactive waste treatment where the ligand inventory is very low.

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