研究了沉淀气浮法回收化肥厂废水中氨氮的工艺及气浮药剂与沉淀物的作用机理。结果表明，用氯化镁和磷酸氢二钠作为沉淀剂时，pH值是重要的影响因素，pH值为10.5时氨氮沉淀率可达95%以上。气浮剂的用量是影响气浮效果的重要因素，在pH值为10.5，气浮剂十二酸钠用量为75mg/L时，气浮回收率可以达到96%以上。经X衍射分析表明，生产的沉淀物以晶态MgNH₄PO·46H₂O为主。经红外光谱分析表明，十二酸钠在磷酸铵镁表面发生化学吸附，从而使其表面疏水而上浮。

The precipitation -air-flotation method is used for removal of ammonia nitrogen from fertilizer plant wastewater.It is found that using magnesium chloride and disodium hydrogen phosphate as precipitation reagent,the precipitation rate of ammonia nitrogen could be more than 95% when pH value is 10.5.The dosage of air-floating agent is an important factor which affects the recovery of air-flotation.The recovery rate of the flotation reaches more than 96% when pH is 10.5 and the dosage of dodecanoic acid is 75mg/L.The precipitates formed at different pH values are analyzed by XRD and it is found to be mainly composed of crystalline MAP (MgNH₄PO₄·6H₂O).The adsorption mechanism between air-floating agent and MAP is chemical adsorption,which is concluded from the results of infrared spectrum analysis.