Study On Ammonia-nitrogen Removal From The Water By The Molecular Sieves/modified Zeolite

Nowadays ammonia-nitroge(NH₄⁺-N) has become a principal aquatic contaminant,in the states. It is one of the focuses of the water treatment field to remove ammonia nitrogen by zeoIite.But the natural zeolite limited to adsorb the orgnic matters and lacked of enough exchange capacity. So it is a tendency of ammonia nitrogen removal by the zeolite to promote the exchange capacity and combine other treatment.At first the natural zeolite was modified by chemical approaches in the research, typing the structures by the CEC, XRD and specific surface area.Through static test, regularity of ammonia-nitroge adsorption by modified zeolite was studied, discussing the effect of influencing factors on ammonia-nitroge adsorption, such as temperature, pH, orgnic matters, initial ammonia concentration and adding amount of modified zeolite. The kinetic was also studied. Through dynamic test, the prossability of mmonia-nitrogen removal by the molecular sieves/modified zeolite was researched, especially discussing the cooperation of molecular sieves in this process.The main results of this research were as follows:1. Under these circumstances: C_NaCl=5mol/L, T=95℃, shaking time=3h, we can get the the right modified zeolite(mmonia removal efficiency=98.56%).The value of CEC promoted from 108.62mmol/100g to 205.05mmol/100g after modify. With XRD analysis, the relatively content of SiO₂ was inceased. specific surface area reached to 26.302 m²/g. The increase of capacity of modified zeolite dued to the CEC promotion. Ammonia adsorption by modified zeolite was an ion exchange process.2. Regularity of ammonia adsorption by modified zeolite as follews:â‘ the increase of initial ammonia concentration benefited adsorption,â‘¡pH=6.00, adsorption capacity reached the climax,â‘¢temperature had little to do with adsorptionâ‘£humic acid had restraining effect on the adsorption, the hinger concentration, the more effect.⑤the ammonia removal efficiency and dsorptive capacity presented negative correlation when adding amount of modified zeolite increased.â‘¥low flow rate profited ammonia removal by modified zeolite, it also coped with the varity of infulent.3. Ammonia adsorption by modified zeolite was rapid. Ammonia removal efficiency reached 60.03% in the first 20min.The process conformed to the law of Fick(R=0.9575). Freundlich and Langmuir isotherm both suited the process, equation of Freundlich isotherm was Q=6.2575C^2.9135(R=0.9677), equation of Langmuir isotherm was: Q=1.2557C/(1+24.065C)(R=0.9315), the result shown that Freundlich isotherm was more suitable for ammonia adsorption by modified zeolite.4. Ammonia-nitrogen removal by the molecular sieves/modified zeolite could reach the sound result.When influent with 10mg/L ammonia concentration and 5mg/L humic acid, the ammonia concentration was below 0.5mgL in theenfluent. Humic acid removal efficiency was up to 70%. With molecular sieves/modified zeolite to treat the practical water contained ammonia-nitrogen, the ammonia concentration was still below 0.5mgL in theenfluent.the experimental results show that through the orgnic matters removal by molecular sieves, humic acid restraining effect on the adsorption decreased, molecular sieves combination modified zeolite promated the ammonia-nitrogen removal.