碳酸根对磷酸钙沉淀反应回收磷的影响

以模拟的厌氧消化液为处理对象，通过小试实验，考察不同初始磷浓度Cp、Ca／P物质的量比、pH和温度下，碳酸根（CO3 2-）对磷酸钙沉淀反应回收磷的影响；利用扫描电镜（SEM）、x射线衍射仪（XRD）和傅里叶变换红外光谱（FT．IR）对沉淀产物进行表征。结果表明，高浓度的CO3 2-对以磷酸钙沉淀反应去除和回收磷的效率影响较大；Cp相同时，CO3 2-浓度（CCO3^2-）越大，P的去除率越低，低C，（20mg／L）时尤为显著；当CCO3^2-相同时，随着Cp的增大，反应速率加快，P的去除率逐渐升高，但升高幅度越来越小；增大Ca／P比和pH能提高P的去除率，降低CO3 2-对磷酸钙沉淀反应的抑制作用，综合考虑实际效果，应选择Ca／P比为3．33，pH为9．0作为适宜的反应条件；升高温度对降低CO3 2-对磷酸钙沉淀反应的抑制作用贡献不大。在Cp为60ITIg／L，Ca／P比为1．67，pH为9．0，温度为20℃的条件下，当CCO3^2-为0时，得到的沉淀产物主要为羟基磷灰石HAP；当CCO3^2-为30mmol／L时，得到的沉淀产物为磷酸钙和碳酸合磷灰石的混合物。

Effect of carbonate on calcium phosphate precipitation for phosphorus recovery

The effect of carbonate （CO23-） on the reaction of calcium phosphate precipitation at different initial phosphorus （P） concentrations, Ca/P ratios, pH values and temperatures were investigated using synthetic anaerobic digestion supernatant as treatment target at bench-scale. The precipitates were characterized by scan- ning electron microscope （SEM） , X-ray Diffraction （XRD） and Fourier transform infrared spectrometer （FTIR） ~ The results showed that the high concentration CO23 had more effect on the efficiency of phosphorus removal and recovery in the precipitated reaction of calcium phosphate. The phosphorus removal efficiency was lower when the CO23- concentration was higher at the same P concentration, especially at the low P concentration （20 rag/L）. The phosphorus removal efficiency was higher but increased slowly when the initial P concentration in- creased and the reaction rate accelerated. The removal efficiency of phosphate also increased with the increase of Ca/P ratio and pH value and decreased with the decrease of CO~- concentration~ The optimized reaction condi- tions were Ca/P ratio of 3.33 and pH value of 9.0 when compared the whole experimental results~ There was no obvious decrease of the inhibitory effect of CO23- on the reaction of calcium phosphate precipitation when the solu- tion temperature increased. Moreover, most of the obtained precipitate was hydroxyapatite under the conditions of no CO3 2- , Cp of 60 mg/L, Ca/P of 1.67,pH value of 9.0 and temperature of 20℃. However, most of the ob- tained precipitates were the mixture of calcium phosphate and carbonate-hydroxyapatite when the C023- concen- tration was 30 mmol/L.