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.
The efficient removal of heavy metals from wastewater and contaminated soil is vital for the environmental remediation and sustainable recycling of metals. Here, we demonstrate that ultrathin MgFe-LDH nanosheets (LDH-S) offer excellent mineralization of Cu 2+ ions in aqueous solutions and soils (ultrahigh uptake capacity of 662 mg/g). The LDH-S can purify real electroplating wastewater (Cu 2+ concentration >5000 mg/L) and trace heavy-metal-containing wastewater (∼10 mg/L) to drinkable levels (below 1 ppb). In the process of Cu 2+ removal, MgFe-LDH is transformed into Cu(Mg)Fe-LDH through surface adsorption and isomorphous substitution. The Cu(Mg)Fe-LDH product could be used directly to remove azo dyes and phosphate anions by adsorption or be processed into metallic copper via a leaching−electroreduction process. The release of Mg 2+ ions by LDH-S during Cu 2+ removal was shown to promote crop growth by acting as magnesium fertilizer, even in acidic soils. This work simultaneously addresses several bottlenecks in heavy metal sequestration, including removal capacity, stability, reusability, and metal recovery.
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