Experimental Study On The Effect Of "Blowing Off + Adsorption" Process On Ammonia Nitrogen Removal From Coal Chemical Wastewater

The rapid development of coal chemical industry makes the harmless treatment of high concentration ammonia wastewater a difficult problem to restrict the high quality development of the industry.At present,the ammonia distillation method is widely used in industry,but the process has the disadvantages of complicated process,high investment cost,and high energy consumption.In this study,the combined process of"blowing off+adsorption"was used to remove high-concentration ammonia nitrogen in coal chemical wastewater.The effects of different factors on the ammonia nitrogen removal were investigated through experiments,and the best process parameters were determined.It is expected that a simple and low-energy ammonia removal process can be developed and applied to production practice.The main findings were as follows:(1)A single factor test study of ammonia nitrogen stripping conditions found that when stripping temperature was 40?(raw water temperature),adjusted pH=11.0,gas-liquid ratio was 2000:1,after 120min of reaction,the ammonia nitrogen content was reduced from 15000mg/L to 1500mg/L,and the removal ratio was about 90%.The orthogonal optimization test obtained the order of influence of each factor of ammonia nitrogen stripping as follows:pH value>stripping time>desorption temperature>gas-liquid ratio.(2)The modified zeolite obtained by using HCl,NaCl,NaOH,and chitosan as modifiers respectively,the salt-modified zeolite had the best effect in removing ammonia nitrogen.BET and SEM analysis showed that the specific surface area of the zeolite was increased after modification.Through XRD and FTIR analysis,the structure of zeolite remained unchanged after modification.(3)A single factor experiment was carried out on the adsorption process of salt-modified zeolite.It was found that adding 5g/100mL zeolite to the coal chemical wastewater,the adsorption temperature was 35?,the pH value was neutral,after120min of adsorption,the ammonia removal ratio was 91.34%,and the remaining ammonia nitrogen content was about 150mg/L.The orthogonal optimization test obtained the order of influence of each factor of adsorption as follows:zeolite dosage>adsorption time>adsorption temperature>modifier concentration>pH value.(4)The analysis of the salt-modified zeolite adsorption model found that the pseudo-second-order kinetic equation model fits the adsorption process to a high degree,and the main effect was the diffusion within the particles;the Langmuir and Freundlich isotherm equations can describe the adsorption process well.The zeolite adsorption process was an endothermic reaction.(5)Recover saturated zeolite with HCl,NaCl,NaOH,and CaCl₂ as regeneration agents,the results showed that when the NaOH concentration was 0.2mol/L,the regeneration time was 8h,and the regeneration temperature was 35?,the regeneration effect of zeolite was the best.After repeated repetitions,the removal ratio of ammonia nitrogen was still more than 90%.BET and SEM analysis showed that the specific surface area of the regenerated zeolite was almost the same as that of the natural zeolite.XRD and FTIR analysis showed that the structure of the regenerated zeolite remains intact.Response surface experiments showed that the order of influence of various factors was:regeneration time>temperature>regeneration agent concentration.(6)After the coal chemical wastewater was treated by the"blowing off+adsorption"process,the ammonia nitrogen content was reduced from 15000mm/L to100mg/L,and the removal ratio reached 99%.The process has the advantages of low investment cost,simple equipment and low energy consumption.