三种有机酸对磷酸钙法回收模拟养猪场污水中磷的影响

采用磷酸钙(Calcium Phosphate,CP)结晶法回收模拟养猪场污水中的磷,考察了不同pH值条件下,3种有机酸(柠檬酸、丁二酸和乙酸)对模拟污水中磷去除率的影响,并利用扫描电镜和X射线衍射仪对结晶产物进行了表征.结果表明,CP结晶反应的最佳pH值约为9.5.在相同pH值条件下,柠檬酸对CP结晶反应中磷的去除效率和速率均有显著影响,高浓度柠檬酸能够完全抑制CP结晶反应,导致磷的去除率小于5%.相比之下,丁二酸和乙酸对磷的去除效率和速率影响不明显.3种有机酸对CP结晶产物的形状没有明显影响,所得产物均呈不定形的块状,但产物体积大小会随有机酸浓度升高而明显减小.不同浓度丁二酸和乙酸存在条件下均能得到羟基磷酸钙(Hydroxylapatite,HAP)晶体,但柠檬酸的存在会影响所得产物晶形.

Effects of three kinds of organic acids on calcium phosphate crystallization from synthetic swine wastewater for phosphorus recovery

In this study, the method of calcium phosphate (CP) crystallization was used to recover phosphorus from simulated swine wastewater. The effects of three organic acids (citric acid, succinic acid and acetic acid) on phosphorus removal efficiency and rate from simulated wastewater at different pH values were investigated. The crystallized products were characterized by scanning electron microscopy and X-ray diffraction. The results demonstrated that the optimum pH value for CP crystallization was about 9.5. Under a defined pH condition, both the phosphorus removal efficiency and the reaction rate were significantly affected by citric acid, and the CP crystallization reaction could be completely suppressed by high concentration citric acid, resulting in low phosphorus removal efficiency (< 5%). By contrast, the effects of succinic acid and acetic acid on the phosphorus removal efficiency and the reaction rate were not obvious. Moreover, three organic acids brought little effects on the shape of the crystallized products, and they all showed amorphous lump. However, the size of the products decreased obviously with the increase of the organic acid concentrations. Hydroxylapatite (HAP) crystals could be obtained in different concentrations of succinic acid and acetic acid, but it could not be achieved when the citric acid existed, since the crystal form of the products might be affected by citric acid.