Indian Journal of Science and Technology

Abstract

Objectives: The current study was focused on preparation of MgO with the different morphologies for enhanced removals of dyes and heavy metal from wastewaters. Methods/Statistical Analysis: The MgO samples were synthesized by a facile precipitation method with the calcination temperature of 500°, its morphology was controlled by altering the concentration of K2 CO3 and Mg(NO3 )2 . As-prepared samples were characterized by TGA, XRD, N2 adsorption/desorption isotherm, FT-IR, FE-SEM and TEM. The performance of as-prepared MgO samples was evaluated by adsorptions of dyes and leads (II) and compared to those of commercial MgO (CM-MgO) and Activated Carbon (AC). Findings: Flower-like MgO (F-MgO) had the high surface area and pore volume (232 m2 /g and 0.575 cm3 /g, respectively) as compared to rod-like MgO (R-MgO) and CM-MgO. The adsorption rate and adsorption capacity of tartrazine on F-MgO were faster and larger, respectively, than those of R-MgO, CM-MgO and AC. The adsorption of F-MgO was achieved equilibrium in 15 min and the adsorption capacity was 65.8 mg/g at the MgO dosage of 0.12 g, initial tartrazine concentration of 50 mg/L, solution pH of 7.0, and temperature of 30°C. The adsorption rate was followed the pseudo second equation and the rate constant was 0.02 g.mg–1.min–1 at 30 °C. The heat of adsorption (∆H° = 19.48 kJ/mol) confirmed the exothermic adsorption of tartrazine and the negative values of G°indicatedthe spontaneous adsorption. The removal efficiency of tartrazine was gradually decreased, but it still remained at 95.2% for the fifth cyclic experiment. In addition, the removal efficiency of Pb (II) on MgO/tartrazine (95%) was much larger than that of F-MgO (about 10%). Application/Improvements: This study gives promising results in concern with treatment of industrial wastewaters before they are charged into the environment.

Keywords: Adsorption, Dye, Heavy Metal, MgO, Wastewater