羟基磷酸钙结晶法回收大型水生植物发酵液中磷酸盐研究

摘要

为有效回收大型水生植物发酵液中磷,选择挺水植物西伯利亚鸢尾(Iris sibirica L.)和圆币草(Hydrocotyle vulgaris)进行发酵试验,分析不同pH值下发酵液中磷回收的效率和纯度,探索羟基磷酸钙(hydroxyapatite,HAP)结晶法回收水生植物发酵液中磷酸盐的可能性.结果表明:西伯利亚鸢尾和圆币草发酵液中钙磷摩尔数比分别为2.7和10,镁磷比分别为1.4和1.6,适合采用HAP法回收磷酸盐.不同水生植物发酵液调节pH值回收磷曲线相似,在pH为8.5时西伯利亚鸢尾和圆币草发酵液磷酸盐回收率分别达到89%和91%,产生的羟基磷酸钙沉降性能良好.X射线荧光光谱分析分析结果表明pH为8.5时沉淀物中P2O5质量分数超过25%,羟基磷酸钙为主要成分.pH调节超过8.5后沉淀物中碳酸钙含量会随着pH上升而不断增加,影响羟基磷酸钙的纯度,因此,回收磷酸盐适合的pH值为8.5.%In order to recover phosphorus from macrophytes fermentation solution effectively, the iris(Iris sibirica L.)and the Hydrocotyle vulgaris were chosen for carrying out fermentation experiments.The efficiency and purity of phosphorus recovery in fermentation broth under different pH values were analyzed and the possibility of phosphorus recovery from macrophytes fermentation solution with the method of hydroxyapatite crystallization was explored.The results showed that it was suitable to recover phosphorus by hydroxyapatite(HAP)crystallization when the ration of Ca to P were 2.7 and 10 and the ratio of Mg to P were 1.4 and 1.6 in the fermentation solutions of Iris sibirica L and Hydrocotyle vulgaris.Different macrophytes fermentation solutions displayed similar process of phosphorus recovery at adjusted pH.The phosphorus recovery rate of iris and H.vulgaris fermentation solutions reached 89%and 91%,respectively when pH value was 8.5 and hydroxyapatite precipitates had good settleability. The results of X ray fluorescence(XRF)analysis indicated that when pH was 8.5, the P2O5mass fraction in the precipitates exceeded 25%and the main component was hydroxyapatite.When pH was adjusted beyond 8.5,the calcium carbonate content in the precipitates would increase with the rise of pH,which would affect the purity of the hydroxyapatite in the precipitates.Therefore,8.5 was the suitable pH value for phosphate recovery.