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

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 mu g 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.

Automated summary

The research highlights the preparation of a stable CaFe-LDH stabilizer with high efficiency in removing nickel ions and exhibits great potential in removing nickel ions from real electroplating wastewater. The isomorphous substitution of Ca2+ by Ni2+ in the laminate of LDH plays a key role in the mineralization process, transforming CaFe-LDH to NiCaFe-LDH, which shows improved electrocatalytic and photocatalytic activities. This work opens up a promising path for the removal of Ni2+ ions from wastewater and utilization of recycled nickel resources.