pH值对磷酸铵镁(MAP)晶体生成的影响研究

The Effect of pH on the Formation of Magnesium Ammonium Phosphate(MAP)Crystal

在MAP生成过程中,溶液的pH的影响和变化都十分明显,重点研究了pH值对MAP生成过程、产量及晶型的影响。溶液的pH值在8~11范围内,随着MAP晶体的形成,溶液的pH值急剧下降,加药8 min后迅速降低至7左右。但是当溶液的pH值增加到12后,其变化变缓,但沉淀物中杂质成分明显增加,基本不再生成MAP晶体。MAP产量影响实验表明:pH值10为最佳MAP生成条件,此时晶体产量高达2.52 g,且沉淀物中杂质成分很少,主要为磷酸铵镁晶体。沉淀物的SEM和XRD谱图分析显示:pH值不同,沉淀物的成分是不一样的。pH值为8~10条件下,主要为磷酸铵镁。pH值为11~12时,沉淀物成分较为复杂,主要为磷酸镁、氢氧化镁、磷酸铵镁的混合物。研究结果表明:在磷酸铵镁晶体的形成过程中,溶液pH值的影响十分显著。

In the process of MAP formation,the influence and change of pH of solution were very obvious,and then,the effects of pH on MAP production,yield and crystal type were studied.In the range of pH8~11,with the formation of MAP crystals,the pH of the solution dropped sharply,and quickly dropped to about 7 after 8 min of addition.However,when the pH increased to 12,the pH of the solution changed slowly,but the impurities in the precipitate increased significantly,and basically no MAP crystal was formed.The results of yield experiment showed that pH10 was the best condition for MAP production,which yield was high to_(2).52 g,and the impurities in the precipitate are few,the component was mainly magnesium ammonium phosphate.The SEM and XRD analyses showed that the composition of the precipitate were different with pH.It was mainly magnesium ammonium phosphate at pH8~10,however,the compositions of the precipitates were more complex at pH11~12,which were mainly the mixture of magnesium phosphate,magnesium hydroxide and ammonium magnesium phosphate.These results showed that the pH of solution has a significant effect on the formation of magnesium ammonium phosphate crystals.