氟化钙参与石煤提钒过程的浸出行为研究

Acid-Leaching of Vanadium from Stone Coal with Calcium Fluoride Addition

研究了氟化钙参与石煤提钒过程的浸出行为,浸出条件为95℃,4 h,1 ml·g-1,15%(体积分数)硫酸和5%(质量分数)氟化钙。在此条件下钒的浸出率可达到92.39%。通过对石煤原矿进行电感耦合等离子体原子发射光谱分析(ICP-AES)、钒价态分析和X射线衍射(XRD)分析,对浸出液进行ICP-AES、X射线光电子能谱(XPS)、19F液相核磁共振(NMR)以及对浸出渣进行XRD和扫描电镜(SEM)分析,整个浸出过程可总结为:氟化钙与硫酸反应生成氢氟酸,氢氟酸对含钒矿物的强破坏性促进钒浸出过程;方解石消耗部分硫酸而生成石膏并释放出二氧化碳;绿泥石和含钒矿物金云母均被完全破坏而释放出V,Al,K,Mg,Si等。氟离子参与钒浸出反应后生成[AlF5]2-和[SiF6]2-络合离子而存在于浸出液中。在强烈搅拌过程中释放出的V(III)被空气中的氧气氧化为VO2+而存在于浸出液中。释放出的Al部分以Al3+存在于浸出液中,另一部分与F生成[AlF5]2-。释放出的Si部分以石英(SiO2)形式留存于浸出渣中,另一部分与F生成[SiF6]2-。正是因为生成的Al-F和Si-F比原有Al-O和Si-O的键能大,钒浸出过程最终会趋向于生成稳定的[SiF6]2-和[AlF5]2-,从而使得整个浸出体系更为稳定,钒浸出更为容易。

The behavior of leaching vanadium from stone coal with calcium fluoride was researched under the conditions of 95℃, 4 h, 1 ml.g-l , 15% （volume fraction） H2SO4 and 5% （mass fraction） calcium fluoride. The leaching rate of vanadium could reach 92.39%. Through the analyses of inductively coupled plasma atomic emission spectroscopy （ICP-AES）, valence state vanadium and X-ray diffractometry （XRD） for the raw ore of stone coal, ICP-AES, X-ray photoelectron spectroscopy （XPS） and I9F liquid nuclear magnetic resonance （NMR） for the leachate, and XRD and scanning electron microscope （SEM） for the leaching residue, the whole leaching process could be summarized that calcium fluoride reacted with sulfuric acid to generate hydrofluoric acid and the hydrofluoric acid solution （HF） could enhance the leaching process owing to its strong destructiveness to vanadium-bearing minerals; calcite con- sumed part of acid to generate CaSO4 and CO2 ; chlorite and vanadium-bearing phlogopite were thoroughly broken down and released V, AI, K, Mg, Si etc. [ A1F5 ] 2 - and [ SiF6 ] 2 - were generated and left in the leachate after F - reacted with other elements in the vanadi- um leaching. In the process of intense stir, the released V（HI） was oxidized into VO2＋ by O2 from air to exist in ]eachate. Part of the released AI existed in leaehate as A13＋ and others combined with F to generate [ A1F5 ] 2-. Part of the released Si existed in residue as SiO2, and the rest combined with F to generate [ SiF6 ] 2 -. It was because the bond energies of A1 - F and Si - F were bigger than that of A1 - O and Si - O, and the generation of [ A1F5 ] 2 - and [ SiF6 ] 2 - made the leaching system more stable and facilitated leaching va- nadium.