Extraction and Separation of Selected Platinum-Group and Base Metal Ions from Nitric Acid Solutions Using Thiodiglycolamides (TDGA) As Novel Extractants

Extraction and Complexation Investigation of Palladium(II) by a Nitrilotriacetate-Derived Triamide Ligand

Effective and selective separation and recovery of the fission product palladium from high-level liquid waste are conducive not only to reducing its hazards to the public health and environment but also to alleviate the pressure on the increasing demand for natural palladium. Herein, the Pd²⁺ extraction in an HNO₃ solution with a nitrilotriacetate-derived triamide ligand NTAamide(n-Oct) and the complexation between them were investigated. Using n-octanol as a diluent, NTAamide(n-Oct) demonstrated an excellent selectivity, strong extractability, and high loading capacity for Pd²⁺ extraction. Combined with the results of single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, electrospray ionization-mass spectroscopy, microcalorimetric titration, and slope analysis, the extracted complexes were determined as [PdL₂](NO₃)₂ and [PdL₂][Pd(NO₃)₄] (where L denotes the NTAamide ligand) in 0.10 and 3.0 mol/L HNO₃ solutions, respectively. The extraction model closely depended on the solvation state of Pd²⁺ in the HNO₃ solution. An ion-pair extraction model was proposed and discussed.

Effect of adding dodecanol as modifier to N,N,N′,N′-tetra-n-hexyl-3,6-dithiaoctane-1,8-diamide silica-based adsorbent on the adsorption behaviors of platinum-group metals and other metals from simulated high-level liquid waste

To adsorb and separate platinum-group metals efficiently from simulated high-level liquid waste, two adsorbents, N,N,N′,N′-tetra-n-hexyl-3,6-dithiaoctane-1,8-diamide (THDTODA)/SiO2-P and (THDTODA + dodecanol)/SiO2-P, were prepared by impregnation of THDTODA with or without dodecanol into macroporous silica/styrene–divinylbenzene copolymer composite particles SiO2-P. The effect of the addition of dodecanol to THDTODA fixed silica-based adsorbents on the separation of platinum-group metals and other metals was evaluated by batch adsorption and chromatographic separation experiments. THDTODA/SiO2-P adsorbed Ru(III) and Rh(III) more than (THDTODA + dodecanol)/SiO2-P did in concentrated HNO3 solution. From the calculated thermodynamic parameters, dodecanol was considered to have little effect on the temperature dependence of the adsorptions of Ru(III), Zr(IV), Mo(VI), and Re(VII) onto the THDTODA adsorbents. Furthermore, in the results of column chromatography experiments, the effects of dodecanol addition on the separation properties were observed for Ru(III), Zr(IV), and Mo(VI), but little effect was observed for Pd(II) and Re(VII).

Adsorption and separation behavior of palladium(II) from simulated high-level liquid waste using a novel silica-based adsorbents

Aiming at selective adsorption and separation of Pd(II) in nitric acid solution, a hybrid soft N and hard O donor adsorbent (TAMIA-EH+TOA)/SiO2–P (P = Polymer) was successfully synthesized. The adsorption performances of (TAMIA-EH+TOA)/SiO2–P adsorbent towards Pd(II) were systematically investigated as a function of contact time, effect of concentration of nitric acid, effect of temperature etc. Adsorption speed of Pd(II) was fairly fast and can reach equilibrium state within only 0.5 h. The distribution coefficient of Pd(II) was more than 103 when [HNO3] = 0.1. Though it decreased gradually with an increase in the concentration of HNO3, the adsorption selectivity of (TAMIA-EH+TOA)/SiO2–P adsorbent towards Pd(II) was still significant than other co-existing metal ions in the whole HNO3 range from 0.1 to 5 M. The adsorption isotherm of Pd(II) onto (TAMIA-EH+TOA)/SiO2–P adsorbent fitted well with Langmuir adsorption model but Freundlich isotherm model. The calculated results of adsorption thermodynamic parameters indicated that the adsorption process of Pd(II) was exothermic and happened in a natural way. Furthermore, the separation chromatography experiment by utilizing (TAMIA-EH+TOA)/SiO2–P adsorbent packed column was carried out. Based on the results of plotted elution curves, it was found that the successful recovery of Pd(II) (96.27%) was achieved by eluting with thiourea solution.