Experimental Study On Adsorption Of Ammonia Nitrogen In Water By Natural And Modified Zeolite

Due to the rapid development of industry and agriculture and the increase of urbanization,the discharge of industrial wastewater and domestic sewage has increased,and water pollution has become an urgent problem.In recent years,emergencies of water pollution have occurred from time to time.Among them,pollution caused by ammonia nitrogen wastewater has caused widespread concern.Therefore,the treatment of ammonia nitrogen wastewater has become a hot topic in scientific research and an important task in today's water treatment industry.The traditional ammonia nitrogen wastewater treatment method has the disadvantages of high investment and operation cost,low treatment efficiency,and difficult operation.Selecting and determining the best treatment technology,and exploring a method of ammonia nitrogen wastewater treatment with good stability,low energy consumption and high efficiency,is the key to solving ammonia nitrogen pollution.The adsorption method has unique advantages due to its simple operation,low operating cost,and wide source of materials.Zeolite is a natural adsorption material with good ammonia nitrogen adsorption performance.China has abundant zeolite reserves and low prices.Using zeolite to treat ammonia nitrogen in wastewater is undoubtedly a promising method.Due to the unique physical and chemical properties of natural zeolites,which have specific adsorption properties,they are widely used in experimental research and practical engineering of ammonia nitrogen adsorption.However,there is a common problem:the adsorption capacity of natural zeolites is not ideal.To achieve the relevant quality of treated water,a large amount of zeolite is often required.Therefore,it is necessary to improve the porosity and cation exchange capacity of the zeolite by physical and chemical modification to further improve the exchange capacity and selectivity of ammonia nitrogen.In this study,Henan Gongyi natural zeolite was selected as the research object.Hydrochloric acid,sodium hydroxide,sodium chloride,silver nitrate,copper chloride,and zinc chloride were used to modify it,and then the natural ammonia and modified zeolite were compared to simulated ammonia nitrogen.The influence of experimental conditions such as pH value,temperature,speed,and dosage on the adsorption effect was investigated.The thermodynamics,adsorption isotherm and kinetics of the adsorption process were analyzed and fitted.SEM(scanning electron microscope),BET(specific surface area test),XRD(X-ray diffraction)characterization of natural and modified zeolites.The experimental results show:1)The best experimental conditions for natural zeolite to adsorb ammonia nitrogen are180r/min,pH value 6.5,dosage 10g/L,30?,and adsorption time 120min.When the initial concentration of ammonia nitrogen is 50mg/L,natural zeolite with a particle size of60-80 mesh is added.Under the optimal experimental conditions,the removal rate of natural nitrogen by zeolite reaches 52.31%,and the adsorption capacity is 2.62mg/g;2)Among the modification methods used in this paper:hydrochloric acid modification,sodium hydroxide modification and zinc chloride modification have no effect on the ability of Henan Gongyi zeolite to adsorb ammonia nitrogen,silver nitrate modification,sodium chloride modification and chlorination Copper modification performance enhances the adsorption capacity of Henan Gongyi zeolite to ammonia nitrogen to varying degrees.The best modification effect is silver nitrate,followed by sodium chloride.The modification effect of copper chloride is relatively poor;3)The experimental method of silver nitrate modification is as follows:100m L of 0.5%silver nitrate solution is added with 1.5g of 60-80 mesh natural zeolite,shaken at 120r/min in a constant temperature shaker at 30°C for 12h and then taken out,Wash with distilled water several times,until no Ag~+is detected in the cleaning solution,dry at 85°C and store it for later use;4)The best experimental conditions for the modified zeolite to adsorb ammonia nitrogen were 180 r/min,pH value 6.5,dosage 5 g/L,30°C,and adsorption time 120 min.When the initial concentration of ammonia nitrogen is 50mg/L,the modified zeolite with a particle size of 60-80 mesh is added.Under the optimal experimental conditions,the removal rate of natural nitrogen ammonia by modified zeolite reaches 95.22%,and the adsorption capacity is9.52mg/g;5)From the analysis of the orthogonal test data,it can be known that during the adsorption of ammonia nitrogen by natural zeolite and modified zeolite,the main order of each factor is:adsorption time>dosing amount>p H value>zeolite particle size>temperature The addition amount has a significant effect on the experimental results,the pH value and the particle size have a certain effect on the experimental results,but the temperature has no significant effect on the experimental results;6)The Langmuir adsorption isotherm can well describe the adsorption of ammonia nitrogen by natural and modified zeolites,which shows that the adsorption of ammonia nitrogen by zeolites is mainly chemical adsorption;7)The results of thermodynamic analysis show that the adsorption process of modified nitrogen and natural zeolite to ammonia nitrogen is exothermic and spontaneous;8)The fitting effect of the quasi-second-order reaction kinetic model is better than that of the quasi-first-order reaction kinetics,which further proves that the adsorption of ammonia nitrogen by natural and modified zeolites is a chemical process.