It is challenging to extract Th (IV) and U (VI) from rare earth elements (REEs) in concentrated acidic solution. Herein, a nanoporous polymer adsorbent P (DVB-VPA) bearing phosphonic acid groups has been synthesized by solvothermal copolymerization of divinylbenzene (DVB) and vinylphosphonic acid (VPA). The maximum adsorption capacity (q max ) for Th (IV) and U (VI) onto P (DVB-VPA) was estimated to be 354.6 and 216.5 mg g −1 at 298 K in 4 mol L −1 of hydrogen nitrate media, which were much larger than most of the adsorbents reported previously. Besides, P (DVB-VPA) exhibited a good selectivity for Th (IV) and U (VI) from REEs in concentrated nitric acid solution, since the values of the selectivity for Th (IV) and U (VI) over La (III), Ce (III), Eu (III), Nd (III) and Sm (III) were 82.2% and 72.5%, respectively. XPS analysis revealed that the adsorption mechanism was achieved through the complexation of P O ligands anchored onto the polymer skeleton of P (DVB-VPA) with thorium and uranium. Due to P (DVB-VPA) showed a larger binding force toward Th (IV) than U (VI), both q max and selectivity for Th (IV) in concentrated hydrogen nitrate media was larger than those for U (VI) on P (DVB-VPA), which has been confirmed by DFT calculations.
Yang Ting,Chen Liping,Chen Wanghua,Zhou Yishan,Gao Haisu,Zhong Tingting
2-Ethylhexyl nitrate (EHN) is an important material, which is produced by concentrated HNO 3 –H 2 SO 4 nitration process. But EHN is not a stable material, especially mixed with acids. To analyze the stability of EHN with concentrated acid under serious condition, four samples (pure EHN, concentrated sulfuric acid with EHN, concentrated nitric acid with EHN, and mixed acid with EHN) and three acids (sulfuric acid, nitric acid, and mixed acid) were measured by differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC) in this paper. The results indicated that concentrated sulfuric acid, concentrated nitric acid, and mixed acid all could decrease the onset decomposition temperature of EHN, especially concentrated sulfuric acid. DSC results also showed that the heat of EHN decomposition with nitric acid is larger than other samples. Based on ARC data, the kinetic parameters and T
D24 (temperature at which TMR
ad is 24 h) were calculated. The activation energy and T
D24 of the EHN with acids, especially with concentrate sulfuric acid, were much lower than the pure EHN. It can be concluded that acids could decrease the stability of EHN and that is an important reason for frequent accidents.
Due to the unique lamellar structures , physicochemical and biological properties, electronegative two-dimensional (2D) materials have been explored for surface modification of carbon fibers reinforced polyetheretherketone (CFR-PEEK) composite. Deposition of electronegative 2D materials based on a porous surface created by concentrated H 2 SO 4 has been studied to promote osteogenesis of CFR-PEEK. Generally, a porous layer will be pre-built on CFR-PEEK through severe corrosion of concentrated sulfuric acid to help the loading of 2D materials . However, the severe corrosion will greatly reduce surface mechanical strength , especially wear resistance and hardness, which increases the risk of collapse or even peeling of the bioactive coating by external force. Herein, instead of the severe corrosion, a mild corrosion by concentrated HNO 3 was applied to modify the surface of CFR-PEEK to pre-create a dense transition layer for the further surface decoration of electronegative 2D materials (graphene oxide (GO) and black phosphorus (BP), representatively). The results indicated that hardness and wear resistance of the dense transition layer were markedly higher than those of the porous layer. Although GO and BP can be both loaded on these two transition layers, –SO 3 H on the porous transition layer showed moderate cytotoxicity, while –NO 2 on the dense transition layer showed good cytocompatibility. The dense transition layer displayed higher mineralized deposition in vitro and new bone formation rate in vivo than the porous transition layer, moreover, GO and BP coatings improved osteogenesis. This work offers inspirations for the construction of electronegative 2D material coating on CFR-PEEK based on chemical transition layers.
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