Layered Double Hydroxides (LDHs) Type Materials Used in Water Treatment

Abstract

Layered double hydroxides (LDHs) or LDHs matrices used for water treatment have been reviewed in this article. These aggregated nanoparticles can be obtained by sol-gel, hydrothermal or coprecipitation method, therefore their shape, size, properties (such as magnetic, acido-bazic, red-ox, texture and assembly) and applications are tailored as a function of synthesis method and process parameters respectively. Among other materials used in water treatment we chose layered double hydroxides generally named LDHs or in particular case hydrotalcites (MgAlLDHs). During calcination layered structure is destroyed giving rise to new structures like mixed oxides partially crystallized. LDHs and calcined LDHs type materials were able to uptake selected products. An important issue for removal of undesirable species for human health was M2+/M3+ cation ratio. Results show a better uptake of anionic compounds for thermally activated LDHs due to their “memory effect”. A large variety of LDHs was investigated in order to demonstrate their adsorption capacity for anionic compounds, cations, gas compounds even microorganisms. Nowadays one of the atractive issues of nanoscience is both the synthesis of these nanostructures and the assembly and organization way but the interest of scientists is to find new properties and applications in order to protect the environment. These cost effective, eco-friendly materials revealed new opportunities for waste water treatment.

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“…Owing to their unique anion-exchange properties, LDHs are considered as very promising materials for removal of pollutants in forms of anions and anion complexes (both inorganic and organic) [18,19]. LDHs are capable of accommodating anionic species with the characteristic height up to few nanometers in the interlayer space.…”

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“…Cations ordering influence the charge density of the layered double hydroxides sheets having thus consequences for some physicochemical properties such as structure, reactivity, organization, surface morphology and exchange capacity of the chemical molecules in the interlayer gallery [20][21][22][23][24][25][26][27][28][29].…”