Study On Hollow Fiber Supported Membrane Mass Transfer For Ammonia Removal From Water

Ammonia is a kind of common pollutant in water. There are many kinds of ammo-nia nitrogen wastewater, so the difficulty of the ammonia nitrogen wastewater treatmentis increasing. There are many kinds of ammonia nitrogen treatment technology, but theyall have some defects. Therefore, the research of the new technology is necessary. Inthis paper, the feed and oil phase are mixed adequately in appropriate conditions. NH4+and NH3is two forms of ammonia in the water. Theirs distribution coefficient betweenthe oil phase and the aqueous phase is studied. The effect of different ammonia concen-trations and feed’s pH on distribution coefficient is also studied. Through the li-quid-liquid extraction experiments, the extracting efficiency is investigated withD2EHPA as carrier in synthesis conditions. The extracting efficiency for differentammonia concentrations is also studied.The mass transfer behavior of ammonia-nitrogen from aqueous media through hol-low fiber supported liquid membrane process consisting of di(2-ethylhexly)phosphoricacid(D2EHPA) in kerosene, supported on the polypropylene hollow fiber membrane,was studied. The influence of the initial pH value and ammonia-nitrogen concentrationin feed phase, the carrier concentration and the acid concentration in stripping phase，thefibre packing density，the flow rate of feed and stripping on ammonia removal is alsocharacterized by the removal rate. The reason of the depressed mass transfer rate forammonia removal is analysed by the contrast test. Through taking these studies, ammo-nia mass transfer mechanism in the hollow fiber membrane is analysed. The main con-clusion is:（1）The distribution coefficient KPwith increasing ammonia concentration in thefeed. Distribution coefficient KPincreases with raised pH. In the same conditions forammonia concentration, NH3’s distribution coefficient is much larger than NH4+’s in the two phase—oil and water.（2）In the process of liquid-liquid extraction, the extraction rate increases with theincrease of material liquid pH and the carrier concentration. Extraction rate drops withthe declining ammonia nitrogen concentration.（3）The effect of HFSLM mass transfer of ammonia nitrogen is characterized bythe removal rate. Ammonia nitrogen removal rate increases with increasing fibre pack-ing density. When the membrane reactor is filled of too much membrane, the masstransfer effect and the removal rate decreases.（4）The removal rate drops with the decrease of the initial concentration ofmaterial liquid. The ability of D2EHPA-kerosene-H2SO4system for ammonia nitrogenmass transfer decreases with the declining ammonia nitrogen concentration.（5）When the material liquid pH is less than9, the extraction process ofD2EHPA-kerosene-H2SO4supported liquid membrane system for ammonia nitrogentransfer mainly relies on the complexation of NH4+and D2EHPA. When the materialliquid pH is more than10, the extraction process of D2EHPA-kerosene-H2SO4support-ed liquid membrane system for ammonia nitrogen transfer mainly relies on thecomplexation of NH3and D2EHPA and ammonia osmosis.（6）Through a group of SLM mass transfer for the multiple groups of ammonianitrogen, single mass removal rate increases with liquid membrane using frequency. butit is a smaller magnitude reduction. It proves D2EHPA-kerosene-H2SO4supportedliquid membrane system for ammonia mass transfer is stable.（7）The initial ammonia concentration in material liquid is2000mg/L, andD2EHPA volume fraction is30%, and stripping agent H2SO4concentration is2mol/L.After several times of regulation pH, ammonia concentration can be reduced to23mg/L.The total removal rate is98.9%. The mass removal rate at single time decreases withincreasing pH regulating times.