废旧镍基高温合金浸出液中铬铝的分离与回收

Separation and Recovery of Chromium and Aluminum in the Leaching Solution of Waste Nickel-Base Superalloys

采用共沉淀法从镍基高温合金的硫酸浸出液中提取分离铬和铝,在热力学分析基础上,研究确定了铬铝沉淀分离的最佳工艺流程及技术参数。热力学分析表明,pH值在4.6~5.4范围内,溶液中的Cr^(3+)和Al^(3+)能够完全沉淀,而Ni^(2+)和Co^(2+)不会发生沉淀。氢氧化钠调节浸出液pH值为4.76,80℃反应20 min的条件下,Cr^(3+)、Al^(3+)、Co^(2+)及Ni^(2+)均会发生氢氧化物沉淀,沉淀率分别为99.95%、99.99%、17%及18.3%。Me-OH^(-)系Eh-pH分析表明,pH>13时,E(CrO_(4)^(2-)/CrO_(2)^(-))≈—0.4 V<0,即Cr^(3+)易被氧化为CrO_(4)^(2-),此时Al(OH)3溶解生成AlO_(2)^(-),镍和钴氢氧化物不会溶解。沉淀物在pH=14,H_(2)O_(2)添加量为0.2 mol/L的条件下溶解,铬和铝分别以CrO_(4)^(2-)和AlO_(2)^(-)的形式进入溶液,镍、钴仍然以沉淀的形式存在;溶液中CrO_(4)^(2-)与氯化钡反应形成BaCrO_(4)沉淀,沉淀率为99.83%。随后用氢氧化钠调节溶液pH值为7,析出Al(OH)_(3)沉淀,达到铬和铝分离回收的目的。本研究为镍基高温合金中有价金属的回收提供了一种高效可行的工艺方法。

Chromium and aluminium were extracted and separated from the sulphuric acid leach solution of nickel-based high-temperature alloys by the co-precipitation method,and based on thermodynamic analysis,the optimum process flow and technical parameters for chromium-aluminium precipitation and separation were studied and determined.The thermodynamic analysis shows that the Cr^(3+)and Al^(3+)in the solution can be completely precipitated in the pH range of 4.5—5.5,while Ni^(2+)and Co^(2+)not be precipitated.Under the condition where sodium hydroxide adjusting the pH of the leaching solution to 4.76 and reacting at 80℃ for 20 min,Cr^(3+),Al^(3+),Co^(2+)and Ni^(2+)undergo hydroxide precipitation,with precipitation rates of 99.95%,99.99%,17% and 18.3%,respectively.The analysis of Eh-pH of the Me-OH^(-)system shows that,when the pH is>13,E(CrO_(4)^(2-)/CrO_(2)^(-))≈—0.4 V<0,Cr^(3+)is easily oxidized to CrO_(4)^(2-).At this point,Al(OH)_(3) dissolves to form AlO_(2)^(-),while nickel and cobalt hydroxides do not dissolve.The precipitate is dissolved at pH14 with an H_(2)O_(2) addition of 0.2 mol/L.Chromium and aluminium enter the solution in the form of CrO_(4)^(2-) and AlO_(2)^(-),respectively,and nickel and cobalt still exist in the form of the residue;CrO_(4)^(2-) in the solution react with barium chloride to form BaCrO_(4) precipitate,with a precipitation rate of 99.83%.Subsequently,the solution pH is adjusted to 7 with sodium hydroxide,causing Al(OH)_(3) to precipitate and achieving the purpose of chromium and aluminium separation and recovery.This study provides an efficient and feasible process method for the recovery of valuable metals from nickel-based high-temperature alloys.