Thermodynamics And Dynamics Research Of Calcium Fluoride Reaction Crystallization

Industry fluoride waste refers to the high concentrations of fluoride wastewater produced by industrial production activities. Fluoride wastewater is a serious threat to human and animal health and ecological balance, so the study of fluoride wastewater treatment technology is particularly important.In the process of fluoride removal from wastewater, Considering the cost problem people usually use calcium salt precipitation method, but calcium salt precipitation is not only a chemical reaction process, which also involves the calcium fluoride crystal nucleation and growth process. If we can master the relevant data of calcium fluoride calcium fluoride in the process of reactive crystallization thermodynamics and dynamics the calcium fluoride in the process of reactive crystallization thermodynamics and dynamics, we can control the whole process of calcium fluoride reaction crystallization, so as to realize efficient removal of fluorine ion in waste water. It has an important scientific value and economic benefits. This paper studied the calcium fluoride reaction crystallization process from two aspects of crystallization thermodynamics and kinetics.1. The thermodynamic process of calcium fluoride reaction was studied, and the related thermodynamics parameters were measured. The solubility and super solubility of calcium fluoride in the water was measured with fluorine ion meter and laser measuring method. It found that the solubility and super solubility of calcium fluoride in the water is two curves which decrease with temperature increasing. And studied the crystallization thermodynamics of calcium fluoride in the conditions of simulating of the rare earth industrial waste water containing fluorine wastewater acid, alkaline, impurity particles, additives and seed. Measured the solubility of calcium fluoride at pH = 6 is a curve with 30℃ as a turning point, and as the temperature increase with decreases first and then increased. The presence of impurity particles and additives are also made an impact on the solubility of calcium fluoride and solubility, Mg2+, EDTA will increase calcium fluoride solubility in the solution; Cl-, Br-, C2H5 OH reduced calcium fluoride super solubility in the solution. The seed will reduce the super solubility, smaller the particle size is, smaller the super solubility is.2. The kinetics process of calcium fluoride reaction crystallization was studied,and the induction period data of calcium fluoride in the pure water was measured.From simulating the conditions of the rare earth industrial waste water containing fluorine wastewater acid, alkaline, impurity particles, additives and seed, studied its influence of calcium fluoride induction period. It was found that the measurement process of induction period of calcium fluoride to conform to the solubility data, proved its accuracy. Under the same external factors influence, the solubility of calcium fluoride and induction period have the same change trend. The experimental analysis the inpact of impurities, additives, ultrasonic field, the seed to calcium fluoride crystal granularity by SEM. The IR and XRD spectra analysis explain that although the introduction of PAM and the ultrasonic field affect the crystal size distribution, but no change to the internal structure of calcium fluoride crystals.