A Dynamic-method Study Of Modified Porous Zeolite Pellet Adsorption Column Removing Ammonia-nitrogen From Water

With the rapid development of the economy, the pollution of water source is increasingly serious. Ammonia-nitrogen ( NH4+ -N ) is an important contaminant for eutrophication of water bodies and environmental pollution. With high concentration of NH4+ -N, natural nitration is restrained, water becomes anoxic, fishes are poisoned, the self-depuration ability of water is reduced, and people's health are threatened. Therefore, our country and many other countries of the world established strict limitation of ammonia-nitrogen in drinking water criterion.As a kind of low-cost nonmetallic mineral, zeolite has unique adsorption and ion-exchange ability. It has good applicability in drinking water treatment. But when it is used to remove pollutants in water, there is an outstanding contradiction between the exchange capacity and the head loss because of the particle size. And we have little knowledge about the process of ion-exchange of zeolite removing NH4+ -N, especially dynamic data.So we plan to produce modified porous zeolite pellet (MPZP), which has both good exchange adsorption ability and high compressive resistance. First, choose the best modifying method and condition of zeolite, produce MPZP and investigate its performance. Then study its treatment effect of low concentration NR4+ -N in column reactor and draw breakthrough curve, investigating such factors as pellet size, velocity of flow, initial ammonia concentration and pH etc. Finally, study the regeneration method and efficiency.Through the research, the conclusion can be drawn that: NaCl modification is the best one comparing with heating, HC1, H2SO4 and NaOH modification, which can raise the NH4+ -N removal ratio obviously by 21%. The most reasonable concentration of NaCl solution is 1mol/L. The best conditions of NaCl modifying are as follows: water bath temperature 70-75 ℃, time 1.5 hours, volume/mass 15ml/g, granularity < 0.125mm. The best preparation condition of MPZP is: modified zeolite (-0.090mm): coal powder: felt matter I =100:6:2, sintering temperature 550°C, time 2hours. Such pellets have good porous structure and enough compressive resistance, with NH4+ -N removal ratio larges than 80%.When the made-up MPZP is used to treat the simulate wastewater in column reactor, the bigger pellets got better treatment effect than that caused by the smaller ones, choosing different pellet size of 3mm, 5mm, 8mm. With low velocity of flow,MPZP and ammonia ion have more chance to contact, so the exchange capacity is high. When getting to the breakthrough point, the lower the ammonia concentration is, the better the treatment effect will be. MPZP has good applicability on low concentration wastewater treatment. The effect of ammonia nitrogen removal is much better when pH=6.4 than that when pH=11.1.When the MPZP is used to treat samples of Yangtse river, the ammonia removal ratio is beyond 80% only through the column one time.The regeneration effect of MPZP is better with higher NaCl solution concentration and velocity of flow. After having been regenerated for 10 times, the exchange capacity of NH4+ -N reduced only by 3.4%.