Cations are positively charged ions4/10/2023 ![]() ![]() In terms of application in the removal of heavy metals, LDHs, as a unique anion intercalation structure, offer numerous advantages: 1) the type of interlayer anion can be modulated by the anion exchange method 2) the metal cations on the layers are flexibly tunable, which immobilized heavy metals into the lattice of LDHs through super-stable mineralization effect 3) the abundant –OH groups on the LDHs laminate make the surface of LDHs rich in binding sites 4) various functional groups (such as -SH, –COOH, and –NH 2) can be modified on the surface or the interlayer of LDHs, which is beneficial to capturing heavy metals through coordination. ![]() ![]() LDHs have been widely used for removal of various pollutants. Generally, the chemical structure formula of LDHs can be described as x + x −, where M 2+ and M 3+ represent divalent and trivalent metal cations (eg., Mg 2+, Ca 2+, Ni 2+, Cu 2+, Zn 2+, Al 3+, Fe 3+, and Cr 3+, etc.), A indicates the interlayer anion,. Layered double hydroxides (LDHs), as a class of two-dimensional (2D), layered anionic clays, consist of positively charged brucite-like host layers, the interlayer anions to balance charge and solvent molecules. Therefore, the exploitation of high efficiency, excellent anti-interference and stable absorbents for removing heavy metals are imminent. , Nevertheless, these traditional absorbents have weak affinity for heavy metals and low removal efficiency. Various absorbents have been used for the heavy metals uptake, such as zeolites, , polymers, , carbonaceous materials, ,, organic resins, etc. Compared with the above methods, adsorption technology is considered to be a potentially efficient and energy-saving strategy. However, some of these methods require the addition of additives, resulting in high pH for effluent and secondary pollution, or low efficiency and high energy consumption, limiting their further applications. , have been committed to removing heavy metals. Numerous techniques such as membrane filtration, , electrochemical treatments, , photocatalytic reactions, , coagulation, etc. The increasing development of industry has brought great economic benefits, but also serious heavy metal pollution, which poses a serious threat to the environment and human health. Herein, according to the unique layered structure of LDHs, we summarized recent progress of LDHs for heavy metals uptake from the following aspects: 1) Based on the tunability and modifiability of the LDHs laminate, we summarized the application of LDHs in removing heavy metals through the super-stable mineralization effect and coordination adsorption mechanism 2) Based on the flexibility of anions in the interlayer of LDHs, we reviewed heavy metals removal by LDHs from anion intercalation and interlayer coordination perspective. It is very important to clarify the removal mechanism of heavy metal ions by LDHs for the subsequent structure design of adsorbent. Due to their low K sp, super-stable mineralization effect, easily modified surfaces, and anion intercalation properties, layered double hydroxides (LDHs) exhibit unique advantages in heavy metal ion removal. With the development of industry and agriculture, heavy metals cause serious pollution to water resources and soil, and it is very urgent to develop highly efficient and low-cost heavy metals removal materials. ![]()
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