Adsorption Behaviors of Platinum Group Metals in Simulated High Level Liquid Waste Using Macroporous (MOTDGA-TOA)/SiO₂-P Silica-based Absorbent

Abstract

As fundamental research for separation of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO 2 -P adsorbent was prepared by impregnation of N,N 0 -dimethyl-N,N 0 -di-noctyl-thiodiglycolamide (MOTDGA) and Tri-n-octylamine (TOA) into silica/polymer composite support (SiO 2 -P). The adsorption behavior of Ru(III), Rh(III), and Pd(II) in simulated HLLW onto the adsorbent were investigated by the batch method to obtain their corresponding equilibrium and kinetic data. The adsorbent showed strong adsorption for Pd(II) and the adsorption reached equilibrium within 2 hr. High distribution coefficient (K d ) values for Pd(II) were obtained in 0.1-1 M HNO 3 concentration. In addition, the use of both MOTDGA and TOA improved adsorption of Ru(III) and Rh(III) better than individual use of them. Especially, the K d value for Ru(III) towards (MOTDGA-TOA)/SiO 2 -P adsorbent was three times larger than that in the adsorption using only with MOTDGA or TOA as extractant. The adsorptions of Ru(III), Rh(III), and Pd(II) followed the Langmuir adsorption model, and were found to be controlled by the chemisorption mechanism.Keywords adsorption; high level liquid waste (HLLW); macroporous silica-based adsorbent; platinum group metals (PGMS)

A Review of Opportunities and Methods for Recovery of Rhodium from Spent Nuclear Fuel during Reprocessing

“…Figure 11 shows the chemical structures of extractants impregnated into silica-polymer supports used for Rh adsorption within this section. In particular, the use of functionalised thiodiglycolamide (TDGA) extractants combined with amine-type extractants in solvent extraction systems has been shown to have a synergistic effect, with extraction of PGMs using both extractants together being higher than the sum of using each extractant separately [111]. To avoid some of the drawbacks associated with solvent extraction, combinations of these extractants have been immobilised into macroporous SiO2-P support materials and deployed in an extraction chromatography process as solid adsorbents.…”

“…Other combinations of ligands (N,N -dimethyl-N,N -di-n-octyl-thiodiglycolamide (MOTDGA), TOA, and dodecanol) impregnated into a microporous silica absorbent have been tested [111]. The adsorbent (MOTDGA+TOA)/SiO 2 -P was compared against (MOTDGA+Dodecanol)/SiO 2 -P and (TOA+Dodecanol)/SiO 2 -P. The latter two adsorbents consisted of single extractants (MOTDGA or TOA) impregnated into the SiO 2 -P support with dodecanol, which was used as a "modifier".…”

“…The uptake of Rh from the same 11-component HLLW simulant was compared using an alternate extractant-impregnated SiO 2 -P material, (DOTDGAA+Dodecanol)/ SiO 2 -P [111]. Adsorption of Rh was slower and less efficient than for TDGAA-Si, but adsorption again increased with increasing HNO 3 concentration.…”

Microanalysis of silica-based adsorbent for effective recovery of radioactive elements

“…Some reprocessing plants have already been commercialized for recovering U and Pu from spent nuclear fuel, and numerous studies on partitioning and transmutation of long-lived radioactive nuclides have been conducted globally [1]. In these studies, several researchers have reported the recovery process of long-lived radioactive nuclides by silica-based adsorbents [2][3][4][5][6][7][8][9][10][11][12][13]. Wei et al developed silica-based adsorbents by impregnating an organic extractant into a styrenedivinylbenzene (SDB) copolymer, which is immobilized in porous silica particles [2].…”

“…In some studies [4][5][6][7][8], SiO 2 -P particles impregnated with N,N,N ,Ntetraoctyl-3-oxapentane-1,5-diamide (TODGA) and 2, 6-bis(5, 6-dialkyl-1, 2, 4-triazine-3-yl)-pyridine (R-BTP) were prepared and applied for group separation MA(III) and trivalent lanthanide (Ln(III)) and for selective recovery of MA(III), respectively, from simulated HLLW. Ito et al impregnated two types of molecules simultaneously into SiO 2 -P particles and studied the application of these adsorbents on the recovery of Cs or platinum group metals (PGM) (N,N -dimethyl-N,N -di-n-octyl-thiodiglycolamide and tri-n-octylamine for Cs recovery [9], and 1,3-[(2,4-Diethylheptylethoxy)oxy]-2,4-crown-6-calix [4]arene (Calix [4]) and 1-dodecanol for PGM recovery [10]). Koma et al assessed the adsorption/elution ability, durability, and after-treatment of several SiO 2 -P adsorbents with different extractants, and the combination of TODGA/SiO 2 -P and R-BTP/SiO 2 -P adsorbents was evaluated as the primary candidate for MA(III) recovery from HLLW [11].…”