(中南大學(xué) 冶金與環(huán)境學(xué)院，長沙 410083)
摘 要: 通過熱力學(xué)計算繪制25 ℃時硫磷混酸分解白鎢礦過程中伴生稀土物種隨pH值以及混酸濃度變化的熱力學(xué)平衡圖，利用這些分析從理論上尋找稀土與鎢綜合提取的技術(shù)，并通過實(shí)驗(yàn)驗(yàn)證此技術(shù)的可行性。結(jié)果表明：稀土離子可與磷酸、硫酸根以及雜多酸形成絡(luò)合物而富集在溶液中，不同的pH條件下稀土被絡(luò)合成陽離子或陰離子。當(dāng)pH＜1時，稀土優(yōu)先與磷酸、硫酸根絡(luò)合形成陽離子；而當(dāng)pH約為1~3時，稀土與雜多酸絡(luò)合成稀土磷鎢雜多陰離子，這些配位可促進(jìn)稀土礦物的分解。實(shí)驗(yàn)還表明了雜多酸對稀土分解有促進(jìn)作用，對于WO3、伴生稀土質(zhì)量分?jǐn)?shù)分別為26.11%和0.13%的白鎢礦，在溫度90 ℃、反應(yīng)時間5 h、磷酸濃度1 mol/L、硫酸濃度2.5 mol/L條件下，稀土La、Ce、Nd浸出率可達(dá)85.61%、45.68%和47.03%。此外，根據(jù)稀土與鎢絡(luò)合物種形態(tài)的差異可設(shè)計稀土與鎢分步或同步提取工藝。
關(guān)鍵字: 稀土礦；白鎢礦；稀土鎢雜多陰離子；提取；熱力學(xué)
（School of Metallurgy and Environment, Central South University, Changsha 410083, China）
Abstract:The thermodynamic equilibrium diagrams for the distribution of species of accompanying rare earth(REE) at different pH values, sulfuric and phosphorous acid concentrations were drawn at 25 ℃. Using these diagrams, the technical methods for extracting rare earth and tungsten were found theoretically and tested by experiments. It appears that rare earth ions can be coordinated by phosphorous acid, sulfate anion or hereopolytungstate anion at different pH values. When the pH value is less than 1, rare earth ions coordinate with phosphorous acid or sulfate anion preferentially and transform to cation cluster. At the pH range of 1-3, rare earth ions coordinate with hereopolytungstate anion and transform to lanthanide containing anion cluster. These complexations are favorable to decompose rare earth minerals. The heteropoly acid can promote the decomposition of rare earth. When the mass fraction of WO3 and rare earths in scheelite are 26.11% and 0.13%, and the concentration of sulfuric and phosphoric acid are 2.5 and 1 mol/L, respectively, the leaching rates of La, Ce, Nd reach 85.61%，45.68% and 47.03% at 90 ℃ for 5 h. Besides, rare earth and tungsten also can be extracted separately or simultaneously as the species of complexations difference.
Key words: rare earths; scheelite; lanthanide containing hereopolytungstate anion; extraction; thermodynamics
