盐卤硼酸盐化学XIII;2MgO.2B2O3. Mgcl2.14H2O结晶动力学研究

本发明对MgO-B2O-MgCl2-H2O浓盐溶液结晶析出氯柱硼镁石(αMgO,αB2O3MgCl.14H2O)的动力学过程进行了研究, 利用单纯形优化法配合Runge-Kutta微分方程组数值解法对实验数据进行处理, 给出了结晶动力学方程, 并对硼在溶液中的存在形式进行了讨论, 提出了结晶反应机理, 同时考察了温度和氯化镁浓度对结晶速率的影响。

Chemistry of borate in salt lake brine XIII: study on crystallization kinetics of 2MgO.2B2O3.MgCl2.14H2O

To determine the optimal conditions for the synthesis of the solid phase 2MgO.2B2O3.MgCl2.14H2O, its crystallization kinetics from solns. containing 0.65 MgO, 1.14 B2O3, and 24, 28, and 32% MgCl2 was studied. The experiments were carried out without stirring. At different time intervals, solution samples were taken for anal., and their d. and pH were determine until the solution d. remained basically constant Then the solid phase was separated and identified by chem. anal., IR spectra, x-ray powder diffraction, and thermal anal. The crystallization kinetic curves were all in reverse S shape. At <40? the crystal growth rate increased with rising temperature, but at >40?it decreased. At constant 30? the crystallization rate decreased with increasing MgCl2 concentration At the experimental temps. and concns., only 2MgO.2B2O3.MgCl2.14H2O crystd. from the solution An appropriate math. modification of Nielsen's mononuclear-layer and polynuclear-layer controlled-growth mechanism was made. The experimental data were fitted using a simple optimum method and a Runge-Kutta solution of a differential-equation system. The kinetic equation of the crystallization reactions is given, and a mechanism of crystallization reactions is proposed.