Characteristics of phosphate ion adsorption by nitrogen-doped carbon-based adsorbents prepared from sucrose, melamine, and urea

Abstract

Sucrose was mixed with melamine and urea, and they were activated with zinc chloride to increase the amine functional groups and quaternary nitrogen (N-Q) on the surface of the sample and improve phosphate ion adsorption. When melamine, urea, sucrose, and zinc chloride were mixed in a 1:1:2:2 weight ratio and activated three times at 550°C, the phosphate ion adsorption amount was highest and its value was 0.40 mmol/g. The total amount of nitrogen in the sample decreased as the number of activation times increased, but the protonated amine functional groups and N-Q that contribute to the adsorption of phosphate increased. The specific surface area increased with increasing the number of activation cycles, and the value was approximately 278 m 2 /g in maximum. This would be supposed to be due to the removal of hydrogen and oxygen from the raw material by the dehydration reaction using zinc chloride at high temperatures, resulting in the formation of pores. The maximum adsorption was observed when the equilibrium solution pH (pHe) was 4.0, indicating that the adsorbent exhibits high adsorption performance in acidic regions. The adsorption isotherm was fitted to the Langmuir model, indicating monolayer adsorption. The estimated maximum adsorption amount (Xm) was 0.61 mmol/g.