Functionalized layered double hydroxide applied to heavy metal ions absorption: A review

Abstract

The use of functional material can help mitigate the pollution by heavy metals, which presents an array of risks to human production and life. This work provides a comprehensive review of the current knowledge on functionalized layered double hydroxide (LDH) as a heavy metal absorption material, by synthesizing the information from a total of 141 relevant publications published since 2005. LDH provides a potentially highly efficient method to adsorb heavy metal ions, which is simple to prepare and of low cost. The lack of functional groups and structural components of pristine LDH, however, limits the absorption capacity and widespread applications of LDH. Through intercalation, surface modification, or loading on substrates, functional groups or structural components are introduced into the pristine LDH to prepare functionalized LDH. In this process, the hydroxyl group and the valence state of [Mg(OH)6] octahedrons play a crucial role. Functionalized LDH can be endowed with selective absorption capacity and enhanced stability and recyclability. After adsorbing heavy metal ions, functionalized LDH can be readily separated from the liquid phase. These aspects are discussed, along with the structure and composition, shape and size, and synthesis methods and research tools of LDH. This work concludes with the discussion of preparation and utilization and a look to the future in terms of identified research needs regarding the preparation, use, and recycling (or upcycling) of economical and environmental-friendly LDH.

Enhanced Photocatalytic Degradation of Methylene Blue by WO3 Nanoparticles Under NIR Light Irradiation

“…In addition, the oxygen adsorbed on the surface of MB can accept electrons and form superoxide radical anions (O 2 ), which also results in the formation of OH upon protonation. These OH and O 2 are responsible for the decomposition of MB under light irradiation ( Zhang et al, 2010 ; Liu et al, 2013 ; Tang et al, 2020 ).…”

The Ability of Composite Ni/Al-carbon based Material Toward Readsorption of Iron(II) in Aqueous Solution

“…The adsorption capacity of NiAl-LDH, Biochar and graphite has decreased signi cantly in the regeneration process, this is because the material has an unstable structure which results in exfoliation when used repeatedly (Palapa et al, 2020d) and structural damage. So it can be concluded that LDH modi cation with carbon-based materials can improve the stability of the LDH structure (Tang et al, 2020) . Thermodynamic parameters were studied through variations in the initial concentration of Fe(II) ions and the adsorption temperature as shown in Figure 7.…”

Layered Double Hydroxides as a Drug Delivery Vehicle for S-Allyl-Mercapto-Cysteine (SAMC)

“…LDHs are very versatile for different technological applications, in particular biological and chemical ones [21], primarily due to their layered structure, which allows for hosting even complex organic molecules, such as drugs and biomolecules, that are intercalated in the large interlayer space with wide flexibility regarding the composition and functionalization [22][23][24][25][26][27][28]. Moreover, there is currently an increasing interest in LDHs due to their properties as heterogeneous catalysts and supports for molecular catalysts [29][30][31] or photocatalysis [32], for fabrication of superhydrophobic surfaces [33,34], water treatment and remediation [35][36][37] and ion-exchanger membranes [38,39]. Interestingly, anion conductivity in LDHs can be modulated by incorporating different anions in the interlayer space, allowing for their use as sensors [40][41][42][43][44] or as fillers in different electrochemical applications, such as fuel cells, supercapacitors and water splitting [45][46][47].…”

“…Moreover, there is currently an increasing interest in LDHs due to their properties as heterogeneous catalysts and supports for molecular catalysts [29][30][31] or photocatalysis [32], for fabrication of superhydrophobic surfaces [33,34], water treatment and remediation [35][36][37] and ion-exchanger membranes [38,39]. Interestingly, anion conductivity in LDHs can be modulated by incorporating different anions in the interlayer space, allowing for their use as sensors [40][41][42][43][44] or as fillers in different electrochemical applications, such as fuel cells, supercapacitors and water splitting [45][46][47].…”