Mingyang Zhao,Xiao Chen,Huiping Zhu,Songqin Xia,Yan Ma,Kyle S. Brinkman,Zhenfeng Tong
This study systematically explored the crystal chemistry of Fe-substituted hollandite (Fe-hollandite) solid solutions (Ba x Cs y )(Fe 2 x + y Ti 8−2 x − y )O 16 ( x + y = 1.33) yielding reliable results through meticulous Rietveld analysis of XRD data. Continuous Cs substitution triggered a monoclinic-tetragonal (M-T) phase transition, enhancing structural stability, as evidenced by increased tolerance factor ( t H ). The transition boundary, controlled by t H = .985, determines the symmetry of the hollandite phase. Unit cell parameters and the local bonding environment were refined, indicating enlarged tunnel sizes/cavities with higher Cs content, attributed to a larger ionic radius (Cs + vs. Ba 2+ ). Comparison between Cs/Ba-O bond distances and tunnel cross-section sizes confirmed effective A-site cation immobilization, hindered by oxygen bottlenecks. Additionally, a refined model was proposed and validated to predict lattice constants of Fe-hollandite precisely. Beyond crystal chemistry evolution with Cs substitution, leaching resistance in the same sample suites was assessed. As Cs content increased, normalized elemental release of A-site cations initially decreased until reaching a minimum at intermediate Cs substitution, then rose again. Ba 0.33 Cs 1.0 Fe 1.66 Ti 6.34 O 16 (i.e., HF5) displayed optimal leaching resistance. Variations in leaching resistance might be influenced by the distortion in [BO 6 ] octahedra and the bonding environment of tunnel cations. This comprehensive analysis highlights intricate correlations between crystal chemistry and leaching resistance, offering insights to guide the design of advanced crystalline nuclear waste forms with enhanced corrosion resistance.
Ma Yao,Shen Yajing,Liu Mingjie,Lin Yuemin,Bao Zongbi,Yang Qiwei,Ren Qilong,Zhang Zhiguo
Pioglitazone has been developed as an effective insulin-sensitizing agent for the treatment of type II diabetes mellitus. Selective hydrogenation of the benzylidenethiazolidinedione exocyclic alkene is a committed step in the industrial manufacturing of pioglitazone. However, the strong coordination between metallic sites of commercial hydrogenation catalysts and benzylidenethiazolidinedione might cause catalyst poisoning and lead to poor activity and selectivity. In this context, an effective and anti-poisoning catalyst with highly dispersed palladium nanoparticles supported on biomass-derived nitrogen-doped carbon with mesoporous structures has been established. A systematic investigation of the structure–activity relationship was performed with a series of Pd/CN x by regulating the ratio of precursors D-glucosamine hydrochloride (GAH) and melamine, and it demonstrated that large specific surface area, rich pore structure and strong Pd–N interaction were essential for the high catalytic performance. The optimal Pd/CN 1.2 catalyst exhibited nearly 100% conversion and 95.5% selectivity under optimized reaction conditions. Remarkably, compared with commercial Pd/C catalyst, Pd/CN 1.2 displayed almost twice the catalytic productivity and provided better poisoning resistance and leaching resistance. Moreover, its stability was also acceptable and good activity could be maintained after exposed in the air for 4 months. Graphical Abstract
危险品化学品经营许可证（带存储）