Separation Science and Technology, Vol.48, No.7, 1049-1055, 2013
Studies on the Separation and Recovery of Palladium from Simulated High Level Liquid Waste (SHLW) Solution with Novel Extractant N,N,N',N'-tetra (2-ethylhexyl) Dithiodiglycolamide DTDGA
The extraction properties of N,N,N',N'-tetra-(2-ethylhexyl) dithiodiglycolamide (DTDGA) have been evaluated for separation and recovery of palladium from simulated high-level liquid waste (SHLW) solution. Extraction of Pd was found to increase with increase in nitric acid concentration up to 4.0M, above which the extraction remains almost constant. Acid uptake studies show 1:1 stoichiometry between DTDGA and HNO3 at nitric acid concentration above 3.0M. The acid uptake constant (KH) was found to be 0.60 which could be due to the presence of two carbonyl groups of amidic moiety. DTDGA has shown very high extractability and selectivity for Pd over other metal ions present in SHLW. The separation factor (SF) for Pd over other metal ions was found to be more than 104. Almost complete back extraction of palladium from organic phase was achieved with 0.01M thiourea in 0.1M nitric acid. Reusability studies of the extractant indicate that DPd remains almost constant even after five successive cycles of extraction and stripping. Two extraction stages will be required for complete extraction of 100mg/L Palladium in 3.0M nitric acid solution using 0.0025M DTDGA/n-dodecane solvent system.