Recovery of palladium by silica/polymer-based 2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine adsorbents from high level liquid waste

Precise recognition and efficient recovery of Pd(II) from high-level liquid waste by a novel aminothiazole-functionalized silica-based adsorbent

Efficient recognition, separation and recovery of palladium from high-level liquid waste (HLLW) not only helps the safe, green and environmentally friendly disposal of nuclear waste, but also is an essential important supplement to overcome the growing shortage of natural palladium resources. Herein, a novel silica-based functional adsorbent named 2AT-SiAaC was prepared by a two-step method, i.e., grafting of 2-aminothiazole (2AT) via the amidated reaction after in-situ polymerization of acrylic monomers on porous silica. SEM, EDS, TG-DSC, BET and PXRD all proved the successful preparation of 2AT-SiAaC, and it exhibited ultrahigh adsorption selectivity for Pd(II) (Kd (distribution coefficient) ≥ 10,344.2 mL/g, SFPd/M (separation factor) ≥ 613.7), fast adsorption kinetics with short equilibrium time (t ≤ 1 h) and good adsorption capacity (Q ≥ 62.1 mg Pd/g). The dynamic column experiments shows that 2AT-SiAaC achieved efficiently separation of Pd(II) from simulated HLLW, and the enrichment coefficients (C/C0) of Pd(II) was as high as about 14 with the recovery rate nearly 99.9% and basically kept the same performance in three adsorption-desorption column cycle experiments. The adsorption mechanism was analyzed by FT-IR, XPS and DFT calculations, and the ultrahigh selectivity of 2AT-SiAaC was attributed to the preferred affinity of the soft N-donor atoms in 2AT for Pd(II). NO3- ions participated in the adsorption reaction to keep charge balance, and the frontier orbital electron density distribution diagram shows the charge transfer in the process of material preparation and adsorption. To sum up, 2AT-SiAaC adsorbent provided a new insight for precise recognition and efficient separation of Pd(II) from HLLW.

Direct separation of minor actinides from high level liquid waste by Me 2 -CA-BTP/SiO2-P adsorbent

Directly separating minor actinides (MA: Am, Cm, etc.) from high level liquid waste (HLLW) containing lanthanides and other fission products is of great significance for the whole nuclear fuel cycle, especially in the aspects of reducing long-term radioactivity and simplifying the post-processing separation process. Herein, a novel silica-based adsorbent Me₂-CA-BTP/SiO₂-P was prepared by impregnating Me₂-CA-BTP (2,6-bis(5,6,7,8-tetrahydro-5,8,9,9-tetramethyl-5,8-methano-1,2,4-benzotriazin-3-yl)pyridine) into porous silica/polymer support particles (SiO₂-P) under reduced pressure. It was found Me₂-CA-BTP/SiO₂-P exhibited good adsorption selectivity towards ²⁴¹Am(III) over ¹⁵²Eu(III) in a wide nitric acid range, acceptable adsorption kinetic, adequate stability against γ irradiation in 1 and 3 M HNO₃ solutions, and successfully separated ²⁴¹Am(III) from simulated 3 M HNO₃ HLLW. In sum, considering the good overall performance of Me₂-CA-BTP/SiO₂-P adsorbent, it has great application potential for directly separating MA from HLLW, and is expected to establish an advanced simplified MA separation process, which is very meaningful for the development of nuclear energy.

Isopentyl-Sulfide-Impregnated Nano-MnO₂ for the Selective Sorption of Pd(II) from the Leaching Liquor of Ores

Conventional separation methods are not suitable for recovering palladium present in low concentrations in ore leaching solutions. In this study, a novel isopentyl sulfide (S₂₀₁)-impregnated α-MnO₂ nanorod adsorbent (BISIN) was prepared, characterized, and applied for the selective adsorption and separation of palladium from the leaching liquor of ores. Batch studies were carried out, and the main adsorption parameters were systematically investigated, in addition to the relevant thermodynamic parameters, isotherms, and kinetic models. The thermodynamic parameters reflected the endothermic and spontaneous nature of the adsorption. Moreover, the experimental results indicated that the Langmuir isotherm model fits the palladium adsorption data well and the adsorption was well described by the pseudo-second-order kinetic model. The main adsorption mechanisms of palladium were elucidated at the molecular level by X-ray crystal structure analysis. Thiourea was found to be an excellent desorption agent, and the palladium-thiourea complex was also confirmed by X-ray crystal structure analysis. The results indicated that almost all of the Pd(II) (>99.0%) is adsorbed on BISIN, whereas less than 2% of the adsorbed Pt(IV), Fe³⁺, Cu²⁺, Ni²⁺, and Co²⁺ is observed under the optimum conditions. The proposed method can be used for the efficient adsorption and separation of palladium from the leaching liquor of ores.