| In most rural areas of northern China,groundwater is regarded as an important source of drinking water.With the rapid development of industry and agriculture and the continuous improvement of people's living standards,a large number of nitrogen-rich fertilizers,The unreasonable disposal and discharge of domestic sewage and industrial wastewater lead to the pollution of ammonia nitrogen and nitrate nitrogen in groundwater.If groundwater contaminated by ammonia nitrogen and nitrate nitrogen enters the human body directly or indirectly,it will increase the risk of disease and carcinogenesis of drinkers.At present,the conventional treatment process is widely used in water purification plants in China.The removal capacity of ammonia nitrogen and nitrate nitrogen is poor,which makes the effluent quality difficult to meet the requirements of sanitary standard GB5749-2006 for domestic drinking water.In this study,the adsorption of nitrate nitrogen by chitosan,a multifunctional polymer material,and the ion exchange of zeolite molecular sieve for ammonia nitrogen were studied.Chitosan modified zeolite(CTS-Z)is a new water treatment material,which can improve the treatment efficiency of ammonia nitrogen and nitrate nitrogen in water at low temperature,and can be used in the process modification of traditional filter.Under the condition of low temperature and high pollution load,the single-stage process can simultaneously treat various pollutants such as ammonia nitrogen and nitrate nitrogen in water.When the adsorption saturation of ammonia nitrogen and nitrate nitrogen was reached,the regeneration of zeolite modified by chitosan was studied in terms of economic and practical application.The main contents of this thesis include the following four aspects.Selection and optimization of regeneration methods for zeolite modified by ammonia nitrogen saturated chitosan:different regeneration methods were adopted for the composite particles adsorbed on ammonia nitrogen saturation,and the concentration of regenerating agent was optimized.The optimum regeneration conditions of zeolite molecular sieve modified by ammonia nitrogen saturated chitosan were obtained by optimizing regeneration time,pH value and regeneration temperature The optimum regeneration method is as follows:the best regeneration agent is NaCl solution with cationic concentration of 0.4mol/L,regeneration time is 24 h,regeneration pH value is 7,regeneration temperature is 30?.Selection and optimization of regeneration methods for zeolite modified by nitrate nitrogen saturated chitosan:different regeneration methods were used to regenerate the composite particles saturated with nitrate nitrogen,and the concentration of regeneration agent was optimized.The optimum regeneration conditions of zeolite molecular sieve modified by nitrate nitrogen saturated chitosan were obtained by optimizing regeneration time,pH value and regeneration temperature The optimum regeneration method is as follows:the best regeneration agent is Na2CO3 solution with cationic concentration of 0.8mol/L,regeneration time is 24 h,regeneration pH value is 7,regeneration temperature is 30?.Study on optimization of CTS-Z regeneration Scheme of ammonia nitrogen and nitrate nitrogen co-saturation:the effect of adding sequence of regenerator on regeneration effect was investigated.The optimal addition order of regenerator was Na2CO3 regeneration first and then nacl regeneration.According to the response surface test,the optimum concentration matching scheme of regeneration agent is obtained.The results show that,The optimal solution for calculating the regenerant by the response surface model is:the total molar concentration of the cation of the Na2CO3 solution is 0.7 mol/L,and the total molar concentration of the cation of the NaCl solution is 0.34 mol/L.The model predicts that the removal rates of ammonia nitrogen and nitrate nitrogen are 72.57%and 29.79%,respectively.Finally,the experimental parameters are given.Number for optimization validation,The relative error between the predicted value and the experimental value is 0.512%and 0.642%,respectively.Study on the regeneration mechanism of chitosan modified zeolite molecular sieve:the regeneration mechanism was studied by adsorption kinetics,adsorption isotherm and adsorption thermodynamics.The results showed that the adsorption process of the regenerated chitosan modified zeolite molecular sieve to ammonia nitrogen and nitrate nitrogen was in accordance with the quasi two stage kinetic model.The adsorption process was chemisorption,adsorption and La The ngmuir adsorption isotherm and the Freundlich adsorption isotherm model fit well,and the adsorption reaction is the process of entropy increasing.Through scanning electron microscope(SEM),energy spectrum analysis(EDS),specific surface area analysis(BET)and Fu Liye infrared spectroscopy(FTIR),the physical and chemical properties of the composite particles are analyzed before and after the regeneration of the chitosan modified zeolite.The regeneration mechanism of molecular sieves shows that the CTS-Z surface of the adsorbed ammonia nitrogen and nitrate nitrogen has a large area of impurities.After regeneration,it can partially restore the uneven mesh structure.The main elements of the adsorbed particles are Si,Al and O after regeneration.The content of Na elements in the adsorbed particles is increased after regeneration,and the pore size and pore volume are also increased to a certain extent.The composite particles are still silicon alumina skeleton.The regeneration performance and mechanism of adsorption particles of chitosan modified zeolite molecular sieve were studied.Through the regeneration research,the cost of replacing filter material in water purification plant was solved,and the purpose of repeated use was achieved,which not only has scientific research value,but also has the value of scientific research.At the same time,it has a high prospect of practical application in the upgrading of water puri fication plant. |
PDF Full Text Request