Super‐Stable Mineralization of Ni²⁺ Ions from Wastewater using CaFe Layered Double Hydroxide

Abstract The dealing/recycling of Ni‐containing wastewater pollution has aroused great attention both from environmental science and resource utilization perspectives. Herein, a classic CaFe‐layered double hydroxide (CaFe‐LDH) stabilizer, which exhibits a super‐stable mineralization efficiency for removing Ni²⁺ ions with a maximum saturated removal capacity of 321 mg g⁻¹ is prepared. This stabilizer can remove not only 10 000 mg L⁻¹ Ni²⁺ ions to a few mg L⁻¹, but also 1 mg L⁻¹ Ni²⁺ ions to 2 µg L⁻¹. Moreover, the CaFe‐LDH shows great mineralization capability for the real Ni‐containing electroplating solution. It is demonstrated by ex situ X‐ray diffraction and extended X‐ray absorption fine structure characterization that the isomorphous substitution of Ca²⁺ by Ni²⁺ in the laminate of LDH dominates the mineralization process, and the CaFe‐LDH is transformed to the corresponding NiCaFe‐LDH accordingly. Further application of the resultant NiCaFe‐LDH shows improved electrocatalytic oxygen evolution reaction and photocatalytic CO₂ reduction activities. This work paves great way for Ni²⁺ ion removal from wastewater and utilization of the recycled Ni resource.