Precise regulation of acid pretreatment for red mud SCR catalyst: Targeting on optimizing the acidity and reducibility

• The optimum SCR activity was realized by tuning the acid pretreatment. • Optimized catalysts showed NO_x conversion above 90%. • The NH₃ and NO adsorption capacity of Al-O₃-Fe is stronger than Fe-O₃-Fe. • The formation of almandine consumes Fe³⁺ and Al³⁺ and weakens their interaction. Red mud (RM), as an alkaline waste, was recently proved to be a promising substitute for the SCR catalyst. Dealkalization could improve the acidity and reducibility of red mud, which were critical for SCR reaction. However, the dealkalization effect depended on the reaction between acid solution and red mud. In this study, we realized the directional control of the chemical state of active sites through tuning the acid pretreatment (dealkalization) process. The pretreatment endpoint was controlled at pH values of 3–5 with diluted nitric acid. When the pH values of red mud were 3 and 5 (CRM-3 and CRM-5), activated catalysts showed NO_x conversion above 90% at 275°C–475°C. The high initial reaction rate, Ce³⁺/(Ce³⁺ + Ce⁴⁺) ratio, and surface acidity accounted for the excellent SCR performance of CRM-5 catalyst. Meanwhile, more Fe³⁺ on the CRM-3 surface improved the NH₃ adsorption. There was a strong interaction between Al and Fe in both CRM-5 and CRM-3 catalysts. DFT results showed that the adsorption capacity of the Al-O₃-Fe for NH₃ and NO is stronger than that of Fe-O₃-Fe, which enhanced the NO_x conversion of the catalyst. However, the almandine was formed in CRM-4, consumed part of Fe³⁺ and Al³⁺, and the interaction between Al and Fe was weakened. Also, deposited almandine on the catalyst surface covered the active sites, thus leading to lower NH₃-SCR activity.     

U PLC- ESI- MS/MS法同时测定水中7种抗生素

采用超高效液相色谱-电喷雾二级质谱联用技术同时测定水中7种抗生素,优化了试验条件.磺胺甲恶唑、诺氟沙星、环丙沙星、氧氟沙星、四环素在1.00 ng/L～1000 ng/L范围内线性良好,定量下限为1 ng/L,土霉素、金霉素在10.0 ng/L-2 000 ng/L范围内线性良好,定量下限为10 ng/L,去离子水和地表水样加标回收率为72.1%-112%,RSD为0.6%～9.2%.     

岩溶地区地下水环境监测难点及解决思路

基于岩溶地区地下水分布特征,结合岩溶地区地下水监测现状,分析了岩溶地区地下水环境质量监测工作中所面临的问题和困难。提出了关于岩溶地区地下水监测的思考和建议,为岩溶地区地下水环境监测提供技术指导。     

Recovery of precious metals from e-wastes through conventional and phytoremediation treatment methods: a review and prediction

Journal of Material Cycles and Waste Management - E-waste, also known as waste from electrical and electronic equipment, is a solid waste that accumulates quickly due to high demand driven by the...