Layered Double Hydroxide Nanomaterial as Highly Efficient Adsorbent and its Recycling after Removal of a Carcinogenic Tartrazine Dye from Wastewater

Abstract

In this work, the tartrazine dye is removed from the wastewater by the layered double hydroxide (LDH) [Zn2-Al-Cl]. LDH materials have proven to be highly effective in removing pollutants, with a low cost of synthesis, non-toxic, and they do not regenerate the sludge. Several parameters were studied, the retention of dye by LDH nanomaterial is optimized for a pH between 6 and 8, the equilibrium retention is obtained after 24 hours, and retention kinetics follows the pseudo-second-order model. The isotherms are the H type, and they follow the Langmuir model, retention capacity reaches 100% for a mass ratio (adsorbate/adsorbent) between 0.1 and 0.5, and the maximum amount retained of the dye is 740.35 mg/g for an initial concentration of tartrazine was 1200 mg/L and 100 mg of mass of LDH. X-ray diffraction (XRD) showed that the synthesized matrix is crystallized in a lamellar structure. Two processes affect the removal of the dye, adsorption of the surface of LDH, and intercalation between the layers. Infrared analysis indicated the appearance of the band's dye in the spectrum of the matrix after retention. Moreover, scanning electron microscopy showed the lamellar character of the two phases obtained before and after retention. The thermodynamics study showed that the process is endothermic, and the adsorption mechanism is governed by physisorption. The LDH nanomaterial is a good adsorbent with low cost, high efficiency, and recyclable.