Preparation of Anion Exchangers Derived from Melamine Sponge and Its Adsorption Characteristics of Nitrate Ion

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Preparation of anion exchangers using melamine sponge (MS) and adsorption of nitrate ion was investigated. Carbonized melamine sponge was prepared at 500°C with ZnCl₂ impregnation (Z6) to develop the pore structure. Z6 was further treated by CH₃I to introduce quaternary nitrogen onto the carbon surface and referred to as Z6-Q. Based on the result of X-ray photoelectron spectroscopy (XPS), Z6-Q contained more quaternary nitrogen than MS and Z6. Adsorption of nitrate ion on Z6-Q reached an equilibrium state the most quickly among the prepared samples. Adsorption kinetic curves indicated that the rate-limiting process was diffusion inside the pore for the adsorption of nitrate ion. In the adsorption of nitrate ion ranging 0.1–0.7 mmol/g, Z6-Q released equimolar chloride ion, suggesting that Z6-Q could have anion exchange sites to adsorb nitrate ion.