[Adsorption Properties of Ammonia Nitrogen in Aqueous Solution by Various Materials]

Focusing on the removal of ammonia nitrogen from polluted water, the absorption properties of five materials (zeolite, maifanite, diatomite, bentonite, and activated carbon) were tested. Results showed that the pseudo-second-order kinetic equation was suitable for data fitting for the five materials. The maximum theoretical adsorption capacities of the five materials were 2.0673 mg·g^-1, 0.9982 mg·g^-1, 0.7580 mg·g^-1, 1.7486 mg·g^-1, and 1.0160 mg·g^-1, respectively, which were close to the experimental value. Chemical-based adsorption was the main mode of adsorption. Data for diatomite were fitted using the Langmuir isotherm equation, and belonged to the single-layer molecular adsorption group, while the other four materials were fitted using the Freundlich isotherm equation, belonging to the multi-layer molecular adsorption group. Moreover, the results showed that the removal rates of ammonia nitrogen by zeolite, diatomite, bentonite, and activated carbon increased with an increase in dosage, and the maximum removal rates were 100%, 10.46%, 49.25%, and 16.87%, respectively. A maifanite dosage of 0.4g achieved the maximum removal rate of 48.85%. At pH 4-10, the adsorption capacities of zeolite and maifanite first increased and then decreased, while that of diatomite, bentonite, and activated carbon slowly increased. The desorption capacity of the five tested materials increased with an increase in the initial concentration of ammonia nitrogen.