(中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083)
摘 要: 通過CaF2溶解實(shí)驗(yàn)對Ca2+-F−-H+-H2O體系的熱力學(xué)性質(zhì)進(jìn)行研究，考察CaF2粒徑、pH等因素對CaF2沉淀溶解−平衡的影響，結(jié)合熱力學(xué)計(jì)算得到影響CaF2沉淀效果的因素。結(jié)果表明：CaF2粒徑對溶液平衡總氟濃度有重要影響，CaF2粒徑越大，其溶解度越小，溶液平衡總氟濃度越低；當(dāng)CaF2粒徑大于16.97 μm時(shí)，平衡總氟濃度低于8 mg/L，而細(xì)顆粒CaF2在溶液中的平衡總氟濃度高于25 mg/L；化學(xué)沉淀法處理含氟廢水時(shí)，應(yīng)盡可能增大CaF2沉淀粒徑，并將反應(yīng)終點(diǎn)pH控制在4.0~10.0之間，達(dá)到降低CaF2溶解度、強(qiáng)化CaF2沉淀效果的目的。
關(guān)鍵字: CaF2；沉淀；熱力學(xué)；粒徑
precipitation-dissolution equilibrium of CaF2
（School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The thermodynamic properties were studied by dissolution experiment. The effects of pH and particle size of CaF2 on the precipitation dissolution equilibrium of Ca2+-F−-H+-H2O system were investigated, and then the factors influencing the precipitation effect were determined combined with the thermodynamic analysis. The results show that the particle size of CaF2 is a critical factor that influences the equilibrium concentration of F. The solubility of CaF2 and equilibrium concentration of F decreases with increasing the particle size of CaF2. The equilibrium concentration of F is less than 8 mg/L with coarse particles larger than 16.97 μm, while it is more than 25 mg/L with fine particles. In order to decrease the solubility of CaF2 and improve the F removal efficiency in the precipitation process, the terminal pH value of the reaction should be controlled between 4.0 and 10.0, while the particle size of the precipitate should be increased as much as possible.
Key words: CaF2; precipitation; thermodynamics; particle size
