方解石去除水体中高浓度磷酸盐的反应动力学

Kinetics of concentrated phosphate removal by calcite

通过X线衍射分析(XRD)、红外光谱分析(FT-IR)、透射电子显微镜(TEM)等检测手段考察方解石除磷的主要产物及其微观形貌,研究除磷过程中主要控制步骤的反应动力学,建立主要控制步骤的最概然动力学模型。研究结果表明:方解石除磷包括生成CaHPO4.2H2O(即DCPD)沉淀与DCPD转化为非晶态磷酸三钙Ca3(PO4)2.xH2O(即ACP)沉淀2个主要步骤,其中,DCPD→ACP转化过程是达到磷酸盐高去除率的主要控制步骤,而阳离子的内扩散是影响反应速率的主要因素;平板内扩散模型较好地反映了该过程的动力学过程;DCPD的转化率X与时间t的函数关系可描述为(1-X)2=-kt,表观活化能约为12.84 kJ/mol;DCPD在反应过程中总体维持板状形貌,在微观尺度上为平板内扩散的动力学模型提供了有力的证据。

The solid remains of phosphate removal by calcite were investigated with XRD,FT-IR and TEM.The kinetics of controlling step was studied and the most probable model was established.The results show that phosphate removal by calcite contains 2 steps,i.e.,the formation of CaHPO4.2H2O（DCPD） and its transformation to Ca3（PO4）2.xH2O（ACP）,and the controlling step is DCPD’s transformation to ACP.Cation internal diffusion is the main influence factor of DCPD→ACP.The kinetics of DCPD→ACP can be represented by the model of flat plate controlled by internal diffusion and the relation between reaction rate（X） and reaction time（t） can be represented as（1-X） 2=-kt;the apparent activation energy is about 12.84 kJ/mol.DCPD keeps shape as flat plate during the process of DCPD→ACP,which gives the micro proof for flat plate controlled by internal diffusion model.