Efficient and Superstable Mineralization of Toxic Cd²⁺ Ions through Defect Engineering in Layered Double Hydroxide Nanosheets

Abstract

Water and soil pollution caused by toxic cadmium ions (Cd 2+ ) is a serious threat to animals, plants, and human health. Discovering low-cost mineralizers which can efficiently and stably immobilize Cd 2+ ions is therefore imperative for wastewater treatment and soil remediation. In this work, we report the successful development of a novel mineralizer for Cd 2+ ion capture. A magnesium−aluminum layered double hydroxide (MgAl-LDH) with a monolayer structure (MgAl-mono) was first prepared and then calcined at 350 °C for 4 h to produce a defective MgAl-mono-350. MgAl-mono-350 offered a very high Cd 2+ removal capacity (1385.5 mg/g at 25 °C) and the ability to reduce the concentration of Cd 2+ in aqueous solution from 100 ppm to less than 50 ppb in 15 min (meeting the discharge standard of industrial wastewater). Detailed characterization and computational studies revealed that MgAl-mono-350 possessed abundant oxygen defects, thereby enabling superstable mineralization of Cd 2+ via isomorphous substitution process,and the Cd 2+ ions are immobilized in the generated CdAl-LDH structure. MgAl-mono-350 also offered outstanding selectivity for Cd 2+ ions over other common ions. This work demonstrates the potential of defect-engineered LDH materials for the selective removal of heavy metals from polluted water.

Superstable Mineralization Coupled with Photocatalysis toward Cr(VI) Remediation Using Layered Double Hydroxide Material

“…prepared Cu 2 O/ZnTi-LDH via an in situ reduction method and utilized it for photocatalytic reduction of Cr­(VI) and degradation of tetracycline, offering new insights into improving the catalytic performance of LDH materials . In addition, numerous studies have demonstrated the potential of LDH materials in effectively mineralizing heavy metals by forming superstable mineralized structures (SSMS). ,, For example, one of our recent works has demonstrated that Ca­(OH) 2 , when used in leather wastewater, can be utilized for the in situ synthesis of CaCr-LDH with an SSMS formed . The obtained CaCr-LDH exhibited remarkable performance in leather tanning, photocatalytic CO 2 reduction, and photocatalytic recycling of precious metals.…”

Boosting the Hydrogen Production Coupling with Electrochemical Methanol Oxidation to Formate Using Monolayered Layered Double Hydroxide Nanosheets

“…By contrast, monolayer LDHs are able to show superior ability because of their larger specific surface area and abundant defect structure. − The O’Hare group reported an innovative approach to synthesizing monolayer LDH powders by using aqueous miscible organic solvent treatment (AMOST), which was also considered possible to be expanded to commercial use . Duan and co-workers have developed separate nucleation and aging steps (SNAS) to prepare various LDH nanomaterials on a ton scale with several successful pilot plants. , Our group has explored the synthesis and application of various monolayer LDHs and has shown better performance than multilayer LDHs in the fields of photocatalysis, − electrocatalysis, and removal of heavy metal ions. , For example, the prepared monolayer NiAl-LDH can be highly selective in the conversion of CO 2 into CH 4 under irradiation with λ > 600 nm, and it completely inhibits the byproduct H 2 precipitation, enabling stronger photocatalytic activity than the multiple layer NiAl-LDH . Through the SNAS method, we can also synthesize monolayer MgAl-LDH, which can be used as an efficient heavy metal adsorption material. , In addition, monolayer LDHs and the functional materials enhance optical performance as smart luminescent materials and have the potential for industrial applications. − As the star material of an efficient water oxidation reaction, NiFe-LDH can be tunable into a monolayer NiFe-LDH structure by a controlled synthesis method, which is expected to improve its MOR ability and promote the generation of H 2 .…”