Yi Zhong,Yun Wang,Zhenliang Yang,Bingqing Li,Jingkun Xu,Zhiyi Wang,Liang Xie,Limei Duan,Fengyun Hu,Mingfu Chu,Rui Gao,Pengcheng Zhang,Bin Bai
In this work, the sintering kinetics of pure UO 2 and 0.5 wt.%MnO-doped UO 2 was studied by a high-temperature dilatometer heated up to 1500°C. In addition, the sintering behavior of pure UO 2 and 0.5 wt.%MnO-doped UO 2 was studied by pressureless sintering technique. The results showed that MnO doping enhanced the grain boundary diffusion of UO 2 , which can effectively decrease the densification temperature and promote grain growth. The sintering temperature of UO 2 was significantly reduced by about 200°C with the addition of 0.5 wt.%MnO. The microscopic morphology studies showed that there were still fine particles agglomerated, forming sintered spheres in the matrix even if no severe agglomeration and bimodal size distribution were observed in raw UO 2 powder. The microstructure evolution of the sintered sphere and UO 2 matrix during the densification process was studied by isothermal sintering. Finally, the present analyses indicated that the densification of UO 2 matrix can be accelerated by adding MnO or increasing the sintering temperature, thus improving the densification inhomogeneity of UO 2 matrix.
Landfill leachate contains high concentrations of hazardous pollutants that require effective treatment before discharge. Membrane distillation (MD) has emerged as a promising approach for leachate treatment, but membrane fouling remains a major challenge for its practical application. This study introduces an innovative in-situ catalytic MD membrane to improve antifouling performance. The MnO₂-doped polyvinylidene fluoride (M-PVDF) membrane was prepared via electrospinning, incorporating an optimized amount of MnO₂ and fluoroalkyl modifier. The M-PVDF membrane demonstrated excellent retention of landfill leachate pollutants across all test cycles, achieving retention rates above 99.23% for non-ammonia foulants. No membrane wetting was observed in M-PVDF during the cyclic tests, whereas conventional PVDF membranes exhibited wetting in the third cycle. The fouled M-PVDF membrane was effectively restored after cleaning with H₂O₂, regaining its original flux and demonstrating robust self-cleaning capabilities. This performance is attributed to the synergistic effects of micro-nano bubbles and MnO₂-catalyzed H₂O₂ free radicals. The proposed in-situ catalytic self-cleaning strategy significantly enhances the antifouling properties of MD, providing a sustainable solution for high-salinity wastewater treatment.
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