The extensive use of selective catalytic reduction (SCR) catalysts will afford many spent SCR catalysts. The mass fraction of the titanium component is over 80% in spent SCR catalysts, but currently, it is usually thrown away without proper recycling. This work aims to develop a clean, green, and economical approach to recovering titanium and regenerating TiO₂ photocatalysts from spent SCR catalysts based on the conversion of the titanium component. This titanium component is converted into metastable α-Na₂TiO₃ with high efficiency (>98%) using a NaOH molten salt method, and the optimal conditions were found to be a roasting temperature of 550 °C, a NaOH-to-spent-SCR-catalysts mass ratio of 1.8:1, a roasting time of 10 min, and a NaOH concentration of 60–80 wt %. And a possible chemical reaction mechanism is proposed. A subsequent hydrothermal treatment of α-Na₂TiO₃ regenerates TiO₂ photocatalysts with high purity (>99.0%) that can satisfy commercial requirements. In addition, the present iron element contained in spent SCR catalysts is doped into regenerated TiO₂ photocatalysts, resulting in providing visible-light-driven photocatalytic activities. The regenerated TiO₂ photocatalysts possess superior photocatalytic degradation capacities for dye pollutants and can be used to efficiently treat wastewater. This work introduces a promising technology for the cyclical regeneration of titanium from spent SCR catalysts.

中文翻译：

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用过的选择性催化还原催化剂绿色回收钛和有效再生TiO ₂光催化剂

选择性催化还原（SCR）催化剂的广泛使用将提供许多废SCR催化剂。废SCR催化剂中钛组分的质量分数超过80％，但目前，通常不进行适当回收就将其丢弃。这项工作旨在开发一种清洁，绿色，经济的方法，该方法可基于钛组分的转化从废SCR催化剂中回收钛并再生TiO ₂光催化剂。此钛组分被转化成亚稳态α-的Na ₂的TiO ₃NaOH熔盐法高效（> 98％），最佳条件是焙烧温度为550°C，NaOH与废SCR催化剂的质量比为1.8：1，焙烧时间为10分钟，NaOH浓度为60-80 wt％。并提出了可能的化学反应机理。随后的水热处理α-的Na ₂的TiO _3个回收物的TiO _2个光催化剂具有高纯度（> 99.0％），其能满足商业要求。另外，废SCR催化剂中包含的本铁元素被掺杂到再生的TiO ₂光催化剂中，从而提供可见光驱动的光催化活性。再生TiO ₂光催化剂对染料污染物具有优异的光催化降解能力，可用于有效处理废水。这项工作介绍了一种从废SCR催化剂中循环再生钛的有前途的技术。