(1. 中南大學(xué) 冶金科學(xué)與工程學(xué)院，長沙 410083；
2. 中南大學(xué) 粉末冶金國家重點(diǎn)實(shí)驗(yàn)室，長沙 410083；
3. 中南大學(xué) 稀有金屬冶金與材料制備湖南省重點(diǎn)實(shí)驗(yàn)室，長沙 410083)
摘 要: 針對硅酸鈉分解白鎢礦的問題，對Ca-Si-W-H2O體系進(jìn)行了熱力學(xué)平衡分析，獲得了一系列平衡關(guān)系圖。理論分析表明，白鎢礦可被硅酸鈉分解，隨著pH值升高，分解固相產(chǎn)物依次為CaSiO3和Ca3Si2O7。在低pH值的CaSiO3穩(wěn)定區(qū)，白鎢礦被硅酸鈉分解，但溶液中鎢濃度較低；在高pH值的Ca3Si2O7穩(wěn)定區(qū)，氫氧化鈉也參與了分解反應(yīng)，鎢濃度隨pH值上升迅速增加。因此，硅酸鈉分解白鎢礦時(shí)可添加適量的氫氧化鈉，以提高鎢礦分解效果。分解實(shí)驗(yàn)驗(yàn)證了理論分析結(jié)果，實(shí)際分解效果變化的趨勢與熱力學(xué)分析一致。硅酸鈉用量是影響浸出總體水平的重要因素，提高試劑濃度或添加氫氧化鈉，能進(jìn)一步提高鎢的浸出率。對于WO3質(zhì)量分?jǐn)?shù)為55.0%白鎢礦，在分解溫度為180 ℃，分解時(shí)間為4 h，體系中硅與鎢、氫氧根與鎢、水與鎢的摩爾比分別為2.0、0.5、35.3的條件下，鎢的浸出率為96.9%。
關(guān)鍵字: 硅酸鈉；白鎢礦；熱力學(xué)；分解
（1. School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
3. Key laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals,
Central South University, Changsha 410083, China）
Abstract:In order to evaluate the feasibility of decomposing scheelite with sodium silicate, thermodynamics of Ca-Si-W-H2O system was studied and a series of equilibrium diagrams were obtained. Theoretical analysis shows that scheelite can be decomposed by sodium silicate under certain conditions and the solid reaction products are CaSiO3 and Ca3Si2O7. At lower pH values, scheelite is decomposed to CaSiO3 by sodium silicate, but W concentration in solution is lower. At higher pH values, it is jointly decomposed to Ca3Si2O7 by sodium silicate and sodium hydroxide, thus the W concentration increases greatly with increasing the pH value. Therefore, it is beneficial to add sufficient sodium hydroxide to the system. Besides, several tests are performed to verify the feasibility of such decomposition, and the experimental results are consistent in trend with the thermodynamic analysis. The dosage of sodium silicate has a remarkable effect on the reaction. Increasing reagent concentration and adding sodium hydroxide can improve the decomposition efficiency. When the WO3 mass fraction in scheelite is 55.0% and the molar ratios of Si to W, OH− to W and H2O to W in the system are 2.0, 0.5 and 35.3, respectively, the W leaching rate reaches 96.9% at 180 ℃ for 4 h.
Key words: sodium silicate; scheelite; thermodynamics; decomposition
