Recent progress in the synthesis of Layered Double Hydroxides and their application for the adsorptive removal of dyes: A review

Layered double hydroxides (LDHs), also known as anionic clays, are lamellar inorganic solids with a brucite-like structure and consist of positively charged metal hydroxide sheets intercalated by anions and water molecules. Choice of LDH is beneficial as it displays properties like simple synthesis procedures, adjustable structure, stability, large surface area, homogeneous positive charge distribution over the surface, interplanar spacing, and versatility to synthesize a variety of composites. Due to these properties LDHs act as efficient adsorbents for wastewater treatment. This review presents a detailed overview of the removal of hazardous organic dyes using different LDHs and LDH-hybrids/composites. The review also incorporates methods of synthesis of various LDHs and composites and the effect of their morphology on dye removal capacity. The effects of adsorption variables such as pH, adsorbent dosage, initial concentration of dye, contact time on the adsorption of these materials are also explained along with adsorption isotherms, kinetics and operative mechanisms. This article incorporates 156 references, majority of which have been taken from the available literature of last 5 years.