Removing Ammonia-Nitrogen From Wastewater By Modified Zeolite

With the development of agriculture and industry, and the rapid growth ofpopulation and urbanization, a large number of ammonia-containing and industrialwastewater is discharged into natural water, it caused serious pollution to the water.The traditional treatments of ammonia nitrogen wastewater have some weakness, forexample, operating cost, high investment and operating difficult. The key of methodto solve pollution is to choose and determine the best processing technology andprocesses that removing ammonia nitrogen stable, high efficiency，low cost. Naturalzeolite is not only rich in deposit but also low in price, so use the zeolite to dealNH3-N wastewater is a promising method undoubtedly.The physical and chemical nature of zeolite make it has some adsorption function.But there is a universal problem that adsorption capacity of zeolite is not high.Therefore, use physical and chemical methods can improve the porosity and exchangecapacity of zeolite, and enhanced the exchange capacity and selectivity to NH3-N.In order to increase the adsorption capacity of zeolite, this paper took fiveways—use the solution of HCl, NaOH and NCl, roast, and NCl-roast modification tomodify zeolite. The experiment concluded that the adsorption capacity of NCl-roastmodification zeolite was better than the other ways. XRD and SEM results showedthat zeolite can cnvert to multiple forms, so that NCl-roast modification zeolite canimprove the NH3-N removal efficienty. The experiment results show that the bestmodified zeolite can be obtained when the concentration of NaCl solution is70g/Land the temperature of roast is300°C. With the dosage of modified zeolite for about1g, the pH value of waste water equals4~8and the reaction time for about30mins,the removal rate of50mL of ammoniac nitrogen wastewater at the concentration of100mg/L will be up to92%.To further discuss the mechanism of zeolite adsorbing NH3-N, the adsorptionprocess was discussed in this study with kinetic theory and thermodynamics, TheNH3-N adsorption data by modified zeolite are well fitted by Freundlich isotherm andLangmuir isotherm；The result showed that the process took place spontaneous- ly,which was an endothermic reaction；The NH3-N adsorption by modified zeolite arewell fitted by pseudo-second-order kinetic model.To validate the feasibility of modified zeolite to deal with practical NH3-Nwastewater,The dynamic adsorption experiments were performed on the basis ofstatic experiment. The conclusion showed that penetration time would be shorterunder the conditions of lower flow rate,higher concentration of NH3-N, and lessadsorbent. The zeolite saturated with ammonium was studied through chemcicalregeneration experiment,the result showed that the regenerative agent NaCl exhibitsbetter effects on zeolite regeneration.The results of experiment can provide with important theoretical foundation for theindustrial application of zeolite, especially to deal with large-scale wastewater.