Technical Study On Continuous Treatment For High Concentration Of Ammonia Nitrogen Wastewater Using Simulated Moving Bed

High concentration of ammonia nitrogen wastewater from industry has been concerned by global environmental scientist all the time because of its strong toxicity and great harm to the environment.However,the present treatment of ammonia nitrogen wastewater using the existing process of ammonia nitrogen wastewater has its obvious shortcomings.Therefore,the research is of great significance on the treatment technology of the high concentration of ammonia nitrogen wastewater.In this paper,the simulated moving bed technology?SMB?was used to remove the high concentration of ammonia nitrogen wastewater of 2500 mg?NH₄⁺?/L,with natural clinoptilolite as ion exchanger,sodium sulfate solution as regenerating agent,cold pure water as the cold eluent and hot water as the hot eluent.From this study,the best condition in experiment were determined:the best number of column for simulated moving bed system was 17;the switching time was 130 min;In adsorption zone,3 columns in series,inflow liquid velocity with 6 m/h at normal temperature was the optimum condition.In regeneration zone,12 columns in series,operated at 90?,regenerant concentration with20%and liquid velocity with 4 m/h was the best condition.When the operation was stable,the concentration of ammonium ion in the outflow of adsorption zone was lower than 5mg/L,ammonia nitrogen removal rate was above 99.8%,and average ammonium ion concentration in the regenerative liquid was up to 19.5 mg/L.To improve the natural clinoptilolite's exchange capacity to ammonia nitrogen,the nature zeolite was firstly modified with saturated sodium chloride solution.From the study of Na⁺-NH₄⁺ion exchange process by retrofit clinoptilolite,the thermodynamic parameters and the adsorption isothem under different temperatures were obtained.Moreover,adsorption isotherm result was satisfactorily correlated using Freundlich model at lower temperature.In addition,a deep study on the column adsorption and regeneration process under different conditions was conducted.The best regeneration flow rate,axial diffusion coefficient,interphase mass transfer coefficient under different number of columns and the relationship between the height of mass transfer zone and feed velocity were obtained based on the outflow curve of the column adsorption and regeneration.It shows that the best liquid velocity for regeneration zone was 3.9 m/h.Futher,the experimental results showed that the concentration of regenerant has the greatest influence on the concentration of ammonia in the regeneration outflow,secondly was regeneration temperature,liquid velocity was the last.In the case of determinate the column regeneration rate,high temperature and low flow rate were good for improving the average concentration of NH₄⁺in regeneration fluid,and the higher of the regenerant concentration,the shorter of the switch time of the system.The effect of liquid velocity,the concentration of regenerant and the regeneration temperature on exchange column regeneration rate were also studied.The results showed that the concentration of regenerant had the greatest influence on the concentration of ammonia in the regeneration outflow,secondly was regeneration temperature,liquid velocity was the last.When fixed the column regeneration rate,high temperature and low flow rate were beneficial to improve the average concentration of NH₄⁺in regeneration fluid,and the higher of regenerant concentration,the shorter of switch time of the system.Besides,the Equilibrium Dispersive Mode?EDM?can well match the SMB continuous ion exchange system when using mathematical tools to analyze the SMB process.It also proved that the model and the method are reasonable.