Simultaneously Removal of Indigo Carmine and Congo Red Anionic Dyes from Aqueous Solutions Using Nickel-Chromium and Zinc-Chromium Layered Double Hydroxides.

The world is currently grappling with unprecedented levels of water pollution, largely attributed to the presence of detrimental chemicals and dyes posing substantial environmental hazards. This study endeavors to develop highly efficient materials capable of extracting anionic dyes from polluted water reservoirs. Utilizing the coprecipitation method, nickel-chrome and zinc-chrome layered double hydroxides (LDH) were synthesized and subsequently analyzed using advanced analytical techniques. The efficiency of both materials in removing anionic dyes Congo Red (CR) and Indigo Carmine (IC) was investigated by analyzing various parameters, including initial solution pH, adsorbent dose, dye concentration, time, and temperature effects. In binary solutions, ZnCr-LDH exhibited a higher adsorption capacity of 109.10 mg g-1 and 78.64 mg g-1 for IC and CR dyes, respectively. The competitive removal of a binary dye mixture is primarily influenced by electrostatic attraction. Isotherm models were employed for analysis, with the Freundlich model found to be the best fit for IC adsorption onto NiCr-LDH and the Sips model for IC adsorption onto ZnCr-LDH. In binary systems, the extended Freundlich and non-modified Redlich-Peterson models provided the best fit to the isotherm data. ZnCr-LDH demonstrated higher removal efficiency than NiCr-LDH. Furthermore, both LDH materials exhibited stability and maintained their activity over four successive cycles. [ABSTRACT FROM AUTHOR]