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针对碱性萃取分离钨、铝过程,根据同时平衡和物质守恒定律,应用现有的热力学数据绘制了25℃时W/Al-H2O系的溶解组分浓度-pH图,Na2CO3-NaHCO3-H2O系R-pH图(R为萃取剂中(R4N)2CO3与(R4N)2CO3+R4NHCO3物质量比例),利用热力学平衡图对碱性萃取钨铝分离过程进行研究。结果表明:[W]T、[Al]T分别为0.5、0.1 mol·L-1,溶液pH为11.5~14.0时钨、铝分别以WO42-、Al(OH)4-存在;pH为4.0~11.5时铝部分以Al(OH)3(am)沉淀析出,钨以阴离子形态存在溶液中;Na2CO3-Na HCO3-H2O系中,NaHCO3含量增加,溶液pH值降低。试验表明,Al(OH)4-能与季铵盐形成萃合物存在有机相中,不会出现沉淀或影响萃取;季铵盐对WO42-的结合能力强于Al(OH)4-;碳酸氢型萃取剂参与钨萃取反应降低萃余液溶液pH值,萃余液pH值低于11.46时铝水解产生氢氧化铝沉淀。串级试验表明,控制萃余液pH为11.59,通过12级逆流萃取,钨、铝的萃取率分别为99.17%、1.20%,说明碱性萃取工艺能够高效的分离钨铝。
According to the principle of simultaneous equilibrium and conservation of matter, the concentration of dissolved component in w / Al-H2O system at -25 ℃ was plotted by using the available thermodynamic data. The concentration of pH-pH in Na2CO3-NaHCO3-H2O system R-pH (R is the mass ratio of (R4N) 2CO3 to (R4N) 2CO3 + R4NHCO3 in the extractant), and the separation process of alkaline extraction of tungsten and aluminum was studied by thermodynamic equilibrium diagram. The results showed that W, T and [Al] T were 0.5 and 0.1 mol·L-1, respectively, and tungsten and aluminum were present as WO42- and Al (OH) 4- when pH was 11.5-14.0. 11.5, the aluminum part precipitated with Al (OH) 3 (am) and the tungsten was in the form of anion. In the Na2CO3-Na HCO3-H2O system, the content of NaHCO3 increased and the pH of the solution decreased. The results showed that Al (OH) 4- could form a complex with quaternary ammonium salt in the organic phase without precipitation or affecting the extraction. The binding ability of quaternary ammonium salt to WO42- was stronger than that of Al (OH) 4-. Hydrogen extractant involved in the extraction of tungsten to reduce the pH of the raffinate solution, the pH of the raffinate below 11.46 aluminum hydrate to produce aluminum hydroxide precipitation. Cascade tests showed that the control raffinate pH 11.59, by 12 countercurrent extraction, tungsten, aluminum extraction rates were 99.17%, 1.20%, indicating that the alkaline extraction process can efficiently separate tungsten and aluminum.