锌对磷酸铵镁和磷酸钙结晶回收磷的影响

以模拟废水为对象,研究了pH及Zn2+浓度对磷酸铵镁(MAP)和羟基磷灰石(HAP)法除磷率的影响,并对不同Zn:P摩尔比条件下除磷所得产物进行了XRD物相分析。结果表明,锌磷共存条件下进行MAP和HAP法除磷,当pH在7.4～8.0时,Zn2+浓度越大,除磷率越高,随着pH继续增加,Zn2+浓度越大,除磷率反而越小。当pH为9.5时,Zn2+浓度从0增加到25mg/L时,MAP法的除磷率从91%下降到82%;而HAP法的除磷率从95%下降到92%,受Zn2+浓度影响较MAP法小。锌磷共存条件下的除磷产物中均含有Zn(3PO4)2,随着溶液中Zn:P增加,产物中Zn(3PO4)2含量越来越多,且HAP法除磷产物纯度受Zn2+浓度影响较MAP法大。

Effect of Zinc on Phosphorus Recovery by Magnesium Ammonium Phosphate and Hydroxyapatite Crystallization

Effects of pH and Zn~(2+) concentration on the phosphate recovery by crystallization of magnesium ammonium phosphate (MAP) and hydroxyapatite (HAP) were studied. The products were analyzed by XRD. Results showed that when pH was in the range of 7.4～8.0, phosphorus recovery efficiency of MAP and HAP crystallization were rising with the increasing of Zn~(2+) concentration. Phosphorus recovery efficiency decreased with the increasing of Zn~(2+) concentration when pH continued to increase. As Zn~(2+) concentration increased from 0 to 25mg/L at pH 9.5, phosphorus recovery efficiency descended from 91% to 82% for MAP while it descended from 95% to 92% for HAP. Phosphorus recovery efficiency of HAP crystallization was less affected by Zn~(2+) concentration at pH 9.5. Both the products of MAP and HAP crystallization contained Zn_3(PO_4)_2 at the condition of phosphate coexisted with zinc in the solution, and content of Zn_3(PO_4)_2 increased with the increasing of Zn:P in the solution, and purity of HAP product was more affected than MAP.