Research On Removing Ammonia Nitrogen In Waste Water Using Chengde Zeolite

With the rapid development of the economy of our country, the pollution of water source is increasingly serious. Ammonia-nitrogen (NH₄⁺-N) is an important contaminant for eutrophication of water body and environmental pollution. With high concentration of NH₄⁺-N, natural nitration is restrained, water becomes anoxic, fishes are poisoned, and the self- depuration ability of water is reduced. To develop an economical and efficient method to control the NH₄⁺-N pollution has become an important program at the present.Natural clinoptilolite is a minieral of hydrated aluminium silicate, consisting of [(Si,Al)O₄] tetrahedroid. The crystral structures of clinoptilolite are special because they have many equal -sized ducts and holes which are occupied by water moleculars and positive ions .The water moleculars can adsorp and deadsorp reversibly without destroying the crystral structures, After dehydration the holes will be able to hold more moleculars, In result clinoptilolite possess adsorption property. On the other hand, the positive ions in ducts and holes are weak in combining with negative ions of aluminium silicate,so they can be replaced by other cation ions reversibly ,still keeping the crystral structure. Because of the above properties of adsorption and ions' exchange, natural clinoptilolites can be widely used in various fields such as agriculture petrochemical indusdtry, architecture, livestock husbandry, enviormental protection and energy application .Compared with synthetical clinoptilolite, natural clinoptilolite is not only rich in deposit but also low in price. Therefore, its exploitation and utilization are calling great attention from the people.This paper deals with the method of modifying Chengde natural clinoptilolite and application to waste water treatment. The effect of clinoptilolite on removal of ammonia-nitrogen is evaluated in the condition of different modified methods, such as inorganic salt, fused-hydro thermally with NaOH and heated .By means of X-ray diffraction and SEM, analyze the reasons of each modified methods. Compare the testing results of ammonia nitrogen removal efficiency, It is found that best removal efficiency wasobtained by 7% NaCl modified clinoptilolite than by other modified clinoptilolite. Then, test the maximum amount of NH4+-N adsorbed on clinoptilolite under batch experiment. Both Langmuir and Freundlich models are used for the evaluation of experimental results. As the reason of well matched with the experimental data, the Freundlich isotherm model is employed.The isothermal adsorption of ammonia-nitrogen violet by chengde clinoptilolite is studied and the data of adsorption kinetics are obtained. According to the Dunwald-Wagner and Paterson models, the effective diffusion coefficients in the clinoptilolite particle are calculated with the equilibrium data and the kinetic curve. With the comparison on their linear dependence, we think that the effective diffusion coefficient calculated by Paterson is more accuracy, which it equals 9.0000x10" cm /s.