Study On Adsorption Characteristics Of Ammonia Nitrogen In Wastewater By Fly Ash Zelite

Ammonia nitrogen is one of the key matters of eutrophication,it'sparticularly critical to decrease the ammonia nitrogen loading in wastewater,especially in the high concentration ammonia nitrogen wastewater.Biological nitrogen removal is widely used in wastewater treatment at home and abroad due to its mature technology,low secondary pollution,and low energy consumption.However,the high strength free ammonia produced in high ammonium wastewater will inhibit the activity of microorganisms,which resulted in the low efficiency of biological nitrification and becoma major difficulty in the treatment of high ammonia nitrogen wastewater.Zeolite has good selective adsorption of ammonia nitrogen in water.Based on optimization of zeolite synthesis from fly ash,the adsorption?pretreatment?test with different initial ammonium concentrations was carried out,and not only realized the effective removal of ammonia nitrogen in wastewater,but also realized the resource utilization of fly ash.The main sources of high ammonia nitrogen wastewater mostly come from industrial wastewater and animal husbandry wastewater.The initial concentration of ammonia nitrogen in the experimental study was determined by the waste water industry discharge standards and the ammoniu concentration in industrial wastewater and animal husbandry raw wastewater.Then,the ammonia nitrogen adsorption characteristics test of the synthetic zeolite from fly ash was performed,and aimed at the swine wasterwater,we used the fly ash zeolite to explore theammonium removal characters and the main factors that influence the ammonium removal.The main contents and conclusions of this paper are as follows:?1?Optimized preparation and characterization of synthetic zeolitesThe fly ash was pretreated by three methods of washing,pickling,washing and pickling.The experimental results show that compared with the other two pretreatment methods,it'sbeneficial to increase the ammonia nitrogen adsorption capacity of synthetic zeoliteswith the preparation of water-pickling-pretreated fly ash and its ammonia nitrogen removal rate is 4.37 times,1.1 times of the zeolitessynthesized with the other two pretreated fly ash,respectively.Compared with the pickling pretreatment,the amount of hydrochloric acid used was reduced by 18.18%.Single-factor experiments were carried out to optimize the conditions for the hydrothermal synthesis of zeolites.The study of effects on the ammonium removal by hydrothermal synthesis time,suitable temperature for hydrothermal synthesis,and optimum liquid-solid ratio of synthetic zeolite was investigated,respectively.and the corressponding appropriate conditions were 48h,95°C,6 mL/g.The physicochemical properties of zeolites synthesized under these conditions were characterized.by XRD,SEM,BET and FT-IR,which indicate that the zeolites with P-type structure were synthesized and its specific surface area was 38 times that of the original fly ash.?2?Experimental study on adsorption of ammonium in simulated wastewater by synthetic zeoliteThe static adsorption experiment was performed in a series of 250mL reactors.A single factor experiment was conducted to determine the suitable oscillating frequency for the adsorption of ammonia from synthetic zeolite,the results indicated that the suitable experimental conditions is of 180r/min,pH of about 7.The ammonia nitrogen removal efficiency was 40.31%to 100%with the initial ammonia concentration of 20 to 500mg/L.And the coexistence of phosphate may weakly weaken the ammonium adsorption capacity of synthetic zeolites,and the ammonia removal rate only drops by1.88%⁶.87%%.The ammonium adsorption by synthetic zeolites matched the pseudo-second-order kinetic equation when the initial ammonia concentration is of 20⁵00mg/L,which indicated that the adsorption of ammonia nitrogen was mainly based on chemical adsorption,and the calculated t_0.5 value was 12.01min,8.83min,6.75min,5.87min,respectively,which are relatively small and indicate the fast adsorption rate of ammonia nitrogen in wastewater.The Langmuir and Freundlich model can describe the isothermal adsorption of ammonia nitrogen by synthetic zeolite and the maximum adsorption capacity of ammonia nitrogen adsorbed by synthetic zeolite is 30.97mg/gunder the experimental conditions.The ammonium adsorption by fly ash zeolite was mainly based on ion exchange in this study.?3?Ammonium removal charactersby synthetic zeolitein swine wastewaterThe synthetic zeolite was used to treat the influent and the supernatant from anaerobic unit of swine wasterwater?ammonia nitrogen concentration was 584mg/L,189mg/L?.The study of ammonium removal influencing factors by adsorption time,adsorbent dosage,and reaction temperature was investigated,respectively.The results show that when the dosage of zeolite in the influent and supernatant is 30g/L and10g/L,respectively,the corresponding ammonia nitrogen removal rate is 49.98%and59.81%,when the reaction proceeding to 2h.The removal rate was basically stable at50.58%to 52.31%and 60.08%to 62%,respectively.The ammonia nitrogen removal capacity of synthetic zeolite increased with the increase of adsorbent dosage,and then gradually stabilized.When the amount is 10⁶0g/L,the removal efficiency of ammonia in the influent water is 21.64%⁶8.34%.When the dosage of synthetic zeolite is 5³0g/L,the ammonia nitrogen removal efficiency in the supernatant is 32.37%⁷5.61%.Compared with simulated wastewater,the presence of metal cations and high concentrations COD in the swine wastewater reduce the ammonia nitrogen removal efficiency about 3.12%¹5.72%,which is not obvious Under experimental conditions,the adsorption of ammonia nitrogen is the result of both ion exchange and adsorption by fly ash zeolite,but it is mainly based on ion exchange.At present,the treatment of high-ammonia nitrogen wastewater by synthetic zeolite from fly ash is mostly in the laboratory research stage,and its influencing factors and parameter optimization in the actual wastewater treatment process need further study.In this dissertation,fly ash was pretreated by washing-pickling pretreatment,and then fly ash zeolite was synthesized.The adsorption characteristics of the fly ash zeolite were clarified,and a small pilot study was conducted on the removal of high strengtn ammonia nitrogen in swine wastewater.The research of this dissertation aims to provide theoretical and technical support for thedevelopment and application of the ammonium adsorption by zeolites from fly ash.