The Research Of Treatment On Chlorine Ammonia Wastewater From Rare-earth Smelting Plant By Chemical Precipitation Method

With the higher requirements in fielded mateial，rare earth coming to our eyes. Peoplepay more and more attention to research its smelting craft which takes lots of pollution to ourenvironment. There is much ammonia nitrogen wastewater in the process of rare earths’ssmelting craft, if they discharge into wave directly or without eligible dispose, it willendanger aquatic animals, plants and people. So, it’s very important to study the treatment onammonia wastewater of the plant’s.In this thesis, it use MAP chemical precipitation method to deal with the chlorineammonia wastewater which produce in the rare-earth smelting plant. Though experiments ofthe choose of phosphorus salt, dosing sequence, single factor’s effects and orthogonal test, weknow the influence factors of the treatment comprehensive and abtain following results:(1) Considering effect of the treatment and the price of drugs which use in theexperiment, it’s better to choose phosphorus salt of Na2HPO4·12H2O during NaH2PO4·2H2O,Na2HPO4·12H2O and Na3PO4·12H2O. In order to get better result, we should add phosphorusfirst, then accommodation value and last magnesium salt.(2) Though studying the impact of single factor, we confirm the best running conditionsis pH=10, n(Mg):n(P):n(N)=1.2:0.9:1, reaction temperature=23~30℃, reaction time=20min,setting time=30min. Under these conditions, the experiments can achieve the bestgoal—ammonium-nitrogen removal rate can reach93%~94%.(3) In the orthogonal test we investigate four factors: pH value, n(Mg):n(N), n(P):n(N)and reaction time. Their order of the effect is pH value＞reaction time＞n(P):n(N)＞n(Mg):n(N). The test also confirm the optimal levels of the factors, that is pH=10,n(Mg):n(N)=1.2, n(P):n(N)=0.9, reaction time=20min. This is fit with the result of singlefactor experiment.(4)With the best running conditions which confirm in experiments upside, we disposeactual wastewater twice. It gets the same ammonia nitrogen removal efficiency as the modelwastewater. The ammonia concentration in outlet water is below15mg/L which is the statestandard.(5)The product of the chemical precipitation method MAP is a kind of good fertilizer. Itcan sell out to make money to buy drugs that used in the method. In this way, we can reducethe cost and attract more and more plant to use this way to dispose Chlorine Ammonia Wastewater from Rare-earth Smelting Plant.