A review of the removal of anions and oxyanions of the halogen elements from aqueous solution by layered double hydroxides

Abstract

The application of layered double hydroxides (LDHs) and thermally activated LDHs for the removal of various fluorine (F(-),BF4(-)), chlorine (Cl(-),ClO4(-)), bromine (Br(-),BrO3(-)) and iodine (I(-),IO3(-)) species from aqueous solutions has been reviewed in this article. LDHs and thermally activated LDHs were able to significantly reduce the concentration of selected anions in laboratory scale experiments. The M(2+):M(3+) cation ratio of the LDH adsorbent was an important factor which influenced anion uptake. Though LDHs were able to remove some target anion species through anion exchange and surface adsorption thermal activation and reformation generally produced better results. The presence of competing anions including carbonate, phosphate and sulphate had a significant impact on uptake of the target anion as LDHs typically exhibit lower affinity towards monovalent anions compared to anions with multiple charges. The removal of fluoride and perchlorate from aqueous solution by a continuous flow system utilising fixed bed columns packed with LDH adsorbents has also been investigated. The adsorption capacity of the columns at breakpoint was heavily dependent on the flow rate and lower than result reported for the corresponding batch methods. There is still considerable scope for future research on numerous topics summarised in this article.

Anti‐Metastatic and Anti‐Angiogenic Activities of Core–Shell SiO2@LDH Loaded with Etoposide in Non‐Small Cell Lung Cancer

“…LDH has been demonstrated as a promising carrier for drug delivery, according to its expandable interlayer space, low cytotoxicity, and high biocompatibility 12, 13, 14, 15. Our team's previous research has already confirmed that layered double hydroxide loaded with etoposide (LDH‐VP16) is very effective in inhibiting A549 cell migration and invasion in vitro via the mTOR/AKT and STAT pathways 16.…”

Uptake Fluoride from Water by Starch Stabilized Layered Double Hydroxide

“…Many reports indicate high fluoride content exist in drinking water in many countries like China, Russia, Pakistan, South Africa [1][2][3]. Use of drinking water containing high concentration of fluoride can cuse dental fluorosis, nervous system diseases, and even cancer [4][5][6].…”

“…and have been regarded as effective adsorbent in reducing the contents of excessive anions, including fluoride [12,[16][17][18]. LDHs are composed of alternating stacked cationic layers and interlayer compensation anions.…”

“…The basic structural formula is: M and M 3+ represent divalent and trivalent cations, respectively, and A n-represents an n-valent anion. Typical LDHs are Mg 6 Al 2 (OH) 16 CO 3 2-·4H 2 O, which have a structure similar to brucite Mg(OH) 2 , and consist of Mg 2+ and Al 3+ ions on both sides, with CO 3 2-anion and water molecules in that middle, like sandwich bread. LDHs own a large interlayer surface, which can capture all kinds of different exchangeable anionic species, provide it high removal efficiency of anionic compounds.…”

A facile and simple synthetic strategy for the preparation of modified NiAl-layered double hydroxide as nanofiller for L-phenylalanine containing poly(amide-imide)s based nanocomposites

“…[17][18][19][20] There is an increasing attention for these materials owing to their several applications in many fields such as catalysis, removal of waste agents from water, stabilizers and rheology modifiers, preparation of pigments, pharmaceutical and cosmetic formulations, symptomatic treatment of peptic ulcer and therapy of digestive disorders, drug and biomolecule hosts, organic-inorganic NCs. [20][21][22][23][24][25][26][27][28][29][30] High-performance polymers are good candidates as matrices in NCs due to their excellent properties, namely high thermal stability, stiffness, flame retardancy, strength, thermo-oxidative stability, toughness, high conductivity, chemical and solvent resistance, low dielectric constant, retained properties at very high temperatures, and long storage periods. [31][32][33][34] Poly(amide-imide)s (PAI)s are one of the most successful classes of high-performance polymers.…”