Experimental Study on Removal of Ammonium-nitrogen from Waste Water by Modified Absorbents

In order to explore the superior adsorbent on ammonium-nitrogen, the comparative study examined the bentonite, zeolite and fly ash respectively modified by hydrochloric acid, sodium hydroxide, sodium chloride, thermal of ammonia nitrogen removal efficiency. The results showed that the zeolite modified by sodium chloride is an ideal adsorbent. Based on the scanning electron microscope and theory, the adsorption mechanism of the sodium chloride modified adsorbent is clarified. The Na+ take place of other cations with larger radius in zeolite, and expand their available space and superficial area. Steric hindrance of the zeolite decreases while diffusion speed increases. Consequently, the adsorption capacity and superficial area are well improved. With the increase in electronegativity of the zeolite modified by sodium chloride after ion exchange and Na+ being easy in exchange for NH4+, the removal of NH4+ becomes more effective. The removal rate of ammonium-nitrogen can be as high as 88.34% when the dosage of initial ammonium-nitrogen is 27.11mg/L, the pH value is 8, the stirring intensity is 150r/min, the dosage of modified zeolite is 2g and the adsorption time is 120 min. The modified zeolite of adsorption to ammonium-nitrogen is really a superior adsorbent which is accorded with Freundlich model.