Synthesis of Hydrotalcite from Bittern, and Its Removal Abilities of Phosphate and Nitrate

Abstract

Abstract-In this study, hydrotalcite was synthesized from bittern solution with addition of AlCl 3 (Mg/Al molar ratio of the solution = 3), and its removal abilities of phosphate and nitrate from aqueous solution were examined. Hydrotalcite can be synthesized from bittern and seawater, and the product from bittern is higher content of hydrotalcite than that from seawater. The product from bittern has a removal abilities of phosphate and nitrate, which were higher than commercial hydrotalcite. The equilibrium adsorption capacity of the product for phosphate and nitrate ions were measured and extrapolated using Langmuir and Freundlich isotherm models, and experimental data are found to fit Langmuir than Freundlich. In the solution with 1 mM of phosphate or nitrate ions, adsorption of phosphate on the product was saturated within 30 min and almost constant after 30 min, while that of nitrate increase within 15 min and then gradually decrease, due to the ion exchange reaction of chlorine and sulphate in the product.Index Terms-Hydrotalcite, bittern, removal of phosphorus and nitrate, anion exchange.