(1. 中南大學 冶金科學與工程學院，長沙 410083；
2. 中南大學 難冶有色金屬資源高效利用國家工程實驗室，長沙 410083)
摘 要: 通過計算反應Gibbs自由能和平衡溶解度對鉻酸鈉堿性液添加石灰除釩過程進行理論分析，結(jié)合紅外光譜研究了含釩溶液的結(jié)構(gòu)變化，研究添加石灰除釩時各因素的影響規(guī)律。結(jié)果表明：在298~373 K的范圍內(nèi)，體系中各離子與氧化鈣生成相應鈣鹽的反應自由能絕對值由大到小的順序為VO3−、CO32−、SO42−、VO43−、CrO42−；同時，各鈣鹽間可能存在相互轉(zhuǎn)化，溶液中CO32−能分解CaCrO4和Ca3(VO4)2等鈣鹽，VO43−能分解CaCrO4。除釩過程中除生成Ca3(VO4)2和Ca2V2O7外，還能生成CaCO3、CaCrO4、CaSO4·nH2O等化合物，這是由于石灰加入量過多所致。溶液結(jié)構(gòu)分析結(jié)果表明：隨著pH值從13降到9左右，釩酸根由VO43−轉(zhuǎn)化成VO43−和V2O74−共存的結(jié)構(gòu)。除釩實驗結(jié)果表明：提高溶液pH值、增大n(CaO)/n(V2O5)或加入高活性石灰乳均可提高除釩率，而溶液中CO32−的存在明顯降低除釩率；加入理論用量3倍的石灰，溶液pH值降至10左右時，除釩率可達到85%，相對于工業(yè)除釩過程釩渣量減少88%左右。
關(guān)鍵字: 鉻酸鈉溶液；石灰；除釩；Gibbs自由能；平衡溶解度
ZHOU Qiu-sheng1, 2, LI Xiao-bin1, 2, PENG Zhi-hong1
（1. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
2. National Engineering Laboratory for Efficient Utilization of Refractory Nonferrous Metals Resources,
Central South University, Changsha 410083, China）
Abstract:The removal of vanadium from the alkaline sodium chromate solution with addition of lime was investigated based on the calculation of reaction Gibbs free energy and equilibrium solubility, and the removal rule of vanadate, as well as the structure of vanadate, was also studied by experiments. The thermodynamic calculation indicates that VO3−, CO32−, SO42−, VO43− and CrO42− can sequentially be precipitated by formation of compound containing calcium at 298−373 K. Meanwhile, the mutual transformation occurs between calcium salts. Ca3(VO4)2 and CaCrO4 can react with CO32−, and CaCrO4 can convert to Ca3(VO4)2 in the existence of VO43−. In addition, the formation of CaCO3, CaCrO4, CaSO4·nH2O as well as Ca3(VO4)2, Ca2V2O7 may account for the excess lime in the removal of vanadium. The structural studies with IR spectra on the pure vanadate solution indicate that some VO43− convert to V2O74− at pH decreasing from about 13 to 9. Experiment results show that increasing the solution pH value and the n(CaO)/n(V2O5) or adding active lime slurry can improve the removal rate of vanadium, but the presence of CO32− is unfavorable to the vanadate removal. The vanadate removal rate can reach 85% and the vanadium residue can be reduced by 88% with 3 times the amount of the theoretical lime required at pH of 10.
Key words: sodium chromate solution; lime; vanadate removal; Gibbs free energy; equilibrium solubility
