Studies Of Removing Ammonia With Modified Zeolite From Micro-polluted Water

Combined with regular tap water process"coagulation-precipitation" and "filter" unit operation, develope a new modified zeolite powder and porous zeolite to remove ammonia nitrogen from micro-polluted water, and study the mechanism of removing process.A new modified zeolite adsorbent is prepared by natural zeolite, chitosan and sodium hydroxide. The adsorbent is used to remove ammonia from micro-polluted water by the process of adsorption and coagulation. The effects of the adsorption time, pH, inital concentration of ammonia and the adsorbent dosages on the removal ratio of ammonia are investigated. The results indicated that when the ammonia concentration in micro-polluted water was 2.51 mg-L-1,1 g-L-1 modified zeolite could remove 70.8%of the ammonia. The modified zeolite powder could be used in modern waterplant.Natural and modified zeolite powder was analyzed by scanning electron microscope (SEM)and energy dispersive analysis of X-ray (EDAX). The SEM results show that:compared with the natural zeolite powder, cluster structure of the modified zeolite powder becomes pore structure, and chitosan is supported on it, forming porous material with bigger inner specific surface area. The EDAX results show that: the modified method can effectively increase the Na+of the zeolite and improve ion exchange properties of zeolite powder.Through screening and comparing the binder,felt matter and sintering temperature, identify the best preparation condition of new modified porous zeolite (NMP zeolite) that of natural zeolite powder as raw materials, sodium silicate(57%) as binder, activated carbon as felt matter ratio to 100:16:2 mixture, drying 2 hours at 104℃after forming, then sintering 2 hours at 500℃. Natural and NMP zeolite was analyzed by SEM,XRD and EDAX. The results show that:compared with the natural zeolite, the surface area and pore size of NMP zeolite are larger,, and the pore volume are more and uniform what it is beneficial for removing ammonia. The zeolite pellet absorption column is used to remove ammonia from micro-polluted water by the process of filter. The effects of flow rat, pH, inital concentration of ammonia and the regeneration conditions on the arnmonia-nitrogen breakthrough curves of ammonia are investigated. NMP zeolite has a small head loss through a long time to deal with large amount of water and good renewable. In the range of natural water pH, lower the flow rat and the inital concentration of ammonia are, higher the ammonia adsorption capacity of NMP zeolite is, the longer the effective absorption. The ammonia adsorption capacity of NMP zeolite are the natural zeolite 2.5 to 3 times in the different flow rat, pH, inital concentration of ammonia of the experimental conditions. Comparied with other regeneration methods, NaCl modification is the best method to regenerate used zeolite. The ammonia adsorption capacity of NMP zeolite is 89.9%of the original one after NaCl modification.