混合稀土精矿碱废水处理过程中的相平衡与热力学模拟研究

A lot of alkali waste water (mainly contained Na+、OH-、F-、PO43-) produced in the process of alkaline of Baiyun obo mixed rare earth concentrate cause serious pollution to the environment. In order to comprehensively recover fluoride and phosphorus resources and realize the recycling of sodium hydroxide from alkali waste water, the project is trying to do applied basic research on the quaternary.system NaF−Na3PO4−NaOH−H2O and its subsystems: determine the accurate solubility data at certain temperature between 298.15K and 373.15K, fit the model parameters by the thermodynamic data and solubility data, build Pitzer-Simonson-Clegg model to express and calculate the Multiple-temperature phase diagram of the system, calculate and predict the data of the quaternary system and its subsystems at any temperature and concentration conditions. Reveal the dissolution and precipitation rules of the fluoride and phosphorus under alkaline conditions, and provide basic data and scientific guidance for the development of alkali waste water treatment process.

白云鄂博混合稀土精矿碱法工艺中产生大量的碱废水(主要含有Na+、OH-、F-、PO43-)对环境造成严重的污染。为了综合回收碱废水中氟、磷资源，并实现氢氧化钠的循环利用，本项目拟对碱废水四元体系NaF−Na3PO4−NaOH−H2O及子体系进行应用基础研究：实验测定298.15K.−373.15K间部分温度下准确的溶解度数据，结合文献热力学数据及溶解度数据拟合多温模型参数，建立能够准确表达和计算体系多温相图的Pitzer-Simonson-Clegg模型，计算和预测该四元体系及其子体系在任意温度和浓度条件下的相平衡数据。揭示碱废水氟磷元素在碱性条件下的溶解和析出规律，为开发碱废水处理工艺提供基础数据和科学指导。

白云鄂博混合稀土精矿碱法工艺中产生大量的碱废水(主要含有Na+、OH–、F–、PO43–)对环境造成严重的污染。为了综合回收碱废水中氟、磷资源，并实现氢氧化钠的循环利用，本项目拟对碱废水四元体系NaF−Na3PO4−NaOH−H2O及子体系进行应用基础研究：首先探究了该四元体系及其子体系离子浓度测定方法，为相图数据的精确测定奠定了基础；其次，采用等温溶解平衡法测定了该四元体系及其子体系273.15K−373.15K间部分温度下准确的溶解度数据，利用数据绘制了多温相图，依据相图得知了各盐间的溶解度变化规律以及析出盐的种类，寻找到碱废水中氟磷资源分离的方法，但分离率较低；最后还探究了利用难溶盐磷酸钙除氟的设想，结果证明分离率也较低。综上所述，本课题的研究结果为构建计算多温相图的热力学模型提供了基础数据，同时也为揭示碱废水氟磷元素在碱性条件下的溶解和析出规律，为开发碱废水处理工艺提供了理论依据和科学指导。.