基于RSM方法优化诱导结晶除氟研究

Optimization of fluoride removal by induced crystallization based on RSM methodology

为了考察氟磷酸钙诱导结晶除氟效果,利用Box-Behnken design(BBD)设计氟磷酸钙诱导结晶除氟实验,建立了以氟离子去除率为响应值的二次回归模型并通过方差分析(ANOVA)比较了n(Ca)/n(F)、n(P)/n(F)、晶种投加量3个参数对氟离子去除率影响的显著性。通过RSM优化氟磷酸钙诱导结晶除氟工艺参数,并通过最优工艺条件下实验结果对模型进行了验证。RSM优化的最佳条件:n(Ca)/n(F)=15、n(P)/n(F)=8.918、晶种投加量9.208 g/L,理论最佳除氟率为97.26%,最佳条件下实际除氟率为95.07%,相对误差为2.3%。SEM结果表明晶种反应前后的表面形貌变化极大,从规则的结晶颗粒变为球型簇状结晶。XRD表征发现通过诱导结晶产生了CaF_(2)、Ca_(10)(PO_(4))_(6)(OH)_(2)、Ca_(10)(PO_(4))_(6)F_(2)、Ca HPO_(4)等晶体,表明氟磷酸钙诱导结晶除氟有多种结晶反应路径。

In order to investigate the fluoride removal effect of calcium fluorophosphate induced crystallization,Box-Behnken design(BBD)was used for calcium fluorophosphate induced crystallization fluoride removal experiments to develop a quadratic regression model with the fluoride ion removal rate as the response value,and to compare the significance of the effects of three parameters〔n(Ca)/n(F),n(P)/n(F),crystalline seed dosage〕on the fluoride ion removal rate by analysis of variance(ANOVA).The process parameters of calcium fluorophosphate induced crystallization for fluoride removal were optimized by RSM,and the model was validated by the experimental results under the optimal process condition.The optimal condition optimized by RSM were n(Ca)/n(F)=15,n(P)/n(F)=8.918,and the amount of crystalline seed dosage as 9.208 g/L,resulting in the theoretical optimal fluoride removal rate of 97.26%.Compared with the actual fluoride removal rate of 95.07%,the relative error was 2.3%.SEM showed that the surface morphology changed greatly before and after the reaction of the crystalline species,from regular crystalline particles to a layer of spherical clustered crystals completely covered.XRD revealed that the induced crystallization produced CaF_(2)、Ca_(10)(PO_(4))_(6)(OH)_(2)、Ca_(10)(PO_(4))_(6)F_(2),and CaHPO_(4),and CaHPO4,indicating that there were multiple crystallization reaction pathways for the removal of fluorine by induced crystallization of calcium fluorophosphate.