Studies on the Separation and Recovery of Palladium from Simulated High Level Liquid Waste (SHLW) Solution with Novel ExtractantN,N,N′,N′-tetra (2-ethylhexyl) Dithiodiglycolamide DTDGA

Abstract

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 4.0 M, above which the extraction remains almost constant. Acid uptake studies show 1:1 stoichiometry between DTDGA and HNO 3 at nitric acid concentration above 3.0 M. The acid uptake constant (K H ) 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 10 4 . Almost complete back extraction of palladium from organic phase was achieved with 0.01 M thiourea in 0.1 M nitric acid. Reusability studies of the extractant indicate that D Pd remains almost constant even after five successive cycles of extraction and stripping. Two extraction stages will be required for complete extraction of 100 mg/L Palladium in 3.0 M nitric acid solution using 0.0025 M DTDGA/n-dodecane solvent system.

Extraction of palladium(II) from nitric acid solutions with diglycolthioamide

“…In previous work, thiodiglycolamide was synthesized by introducing a sulfur atom into diglycolamide to substitute the oxygen atom in the ether linkage for extraction of Pd(II) (Narita et al, 2004;Ruhela et al, 2010Ruhela et al, , 2013. The oxygen atoms in the amido linkages in diglycolamides have not been synthesized and their extraction behaviors also have not been studied before.…”

Efficient and Selective Removal of Palladium from Simulated High-Level Liquid Waste Using a Silica-Based Adsorbent NTAamide(C8)/SiO2-P

“…High-level liquid waste (HLLW) generated from fuel treatment contains more than 40 elements, such as Ru, Rh, Pd, Tb, Tc, Cs, Sr, Mo, I, etc. [ 1 , 2 ] Palladium is a platinum-group metal with a silver luster. The palladium in the HLLW includes stable isotopes 104 Pd (17 wt.%), 105 Pd (29 wt.%), 106 Pd (21 wt.%), 108 Pd (12 wt.%), and 110 Pd (4 wt.%), and radioactive isotope 107 Pd (17 wt.%).…”

“…Solvent extraction is a widely used method for recovering palladium from HLLW [ 1 , 2 , 18 , 19 ]. It is well known that Pd(II) belongs to a soft Lewis acid, and can easily complex with the ligand containing a soft-donor N or S atom [ 20 ].…”