Extraction-electrodeposition (EX-EL) process for the recovery of palladium from high-level liquid waste

Extraction-electrodeposition (EX-EL) process has been developed for the quantitative recovery of palladium from nitric acid medium and fast reactor-simulated high-level liquid waste (FR-S-HLLW). The process exploits some characteristic properties of room temperature ionic liquid, tri-n-octylmethylammonium nitrate (TOMAN), for quantitative and favorable recovery of palladium. Extraction of palladium (II) from FR-S-HLLW and nitric acid medium by a solution of 0.5 M TOMAN in chloroform has been studied in detail. More than 60% of palladium was extracted in a single contact of equal volumes of organic and aqueous phases and nearly five contacts were required for quantitative extraction. The electrochemical behavior of palladium (II) present in the organic phase was investigated at stainless steel electrode by cyclic voltammetry. A surge in cathodic current occurring at a potential of -0.5 V (vs. Pd) was due to the reduction of palladium (II) to palladium (0). The kinetics of electrodeposition was followed by the UV-VIS absorption spectrum of palladium present in organic phase and under the given conditions nearly 20 and 35 h were required for the quantitative deposition of palladium from organic phase, which was obtained after extraction of palladium from 4 M nitric acid and FR-S-HLLW, respectively. Decontamination of palladium from other fission products during extraction and electrodeposition was studied and the results are reported in this article.