Zn-Al layered double hydroxide nanoparticles for efficient removal of food dyes from wastewater

Abstract

The ability of layered double hydroxides clay (LDH) produced from ZnAl-NO3 to remove Sunset Yellow FCF (E110), Azorubine (E122), Tartrazine (E102), and Brilliant Blue FCF (E133) from an aqueous solution was studied. The effects of various variables on adsorption were studied. The obtained results show that the adsorption of various food dyes depends on the initial concentration, dose, pH, contact time, and temperature. The adsorption capacities at an equilibrium time of 40 min for E133, E122, E110, and E102 were 18.21, 21.46, 13.19, and 20.58 mg/g, respectively. The adsorption equilibrium data for aqueous solutions were analyzed using Langmuir and Freundlich isotherms and a thermodynamic study. Adsorption kinetics data for aqueous solutions was studied using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The morphology for Zn-Al LDH was investigated by scanning electron microscopy (SEM) and BET (pore size = 0.004 cc/g). Equilibrium data were studied by Freundlich, Langmuir, and Temkin isotherms. As for thermodynamics, the value of ∆H° is negative, which means that the adsorption method is exothermic at a temperature range of 288–338 K. ∆S ° is a negative value indicating that the randomness is low, ∆G° is also negative means that the reaction is spontaneous. The FTIR spectroscopic analysis of LDH before and after the adsorption also confirms that the adsorption of food dyes was smooth and spontaneous on Zn-Al LDH providing an excellent and easy-to-use adsorption method for industrial application of wastewater treatment.