摘要
To investigate the behaviors of Cu^(2+)and Ni^(2+)with the change of conditions in Cu_(2+)−Ni_(2+)−NH_(3)−NH_(4)+−C_(2)O_(4)^(2-)−H_(2)O reaction system,mathematical models of thermodynamics based on the principle of mass conservation were established.The simulation results indicate that the precipitation of metal ions from the aqueous phase is a complicated dynamic equilibrium process,during which the coordination reactions of Cu^(2+)and Ni^(2+)with NH3 forming[Cu(NH3)n]^(2+)(n=3−5)and[Ni(NH3)m]^(2+)(m=3−6)are predominant under high pH conditions,respectively.The pH ranges for the simultaneous precipitation of Cu^(2+)and Ni^(2+)are 2.0−6.5 and 2.0−5.5 when[NH3]T equals 0.6 and 4.2 mol/L,respectively,with the prefixed[C_(2)O_(4)^(2-)]T of 0.6 mol/L.Due to the fractional precipitation of Cu^(2+)and Ni^(2+),Cu−Ni composite is obtained after the thermal decomposition of Cu−Ni oxalate complex salts prepared in a pure water system when pH>7.0.By applying the mixed solvent(water/ethanol)as the precipitation medium,the Cu−Ni alloy rods can be finally fabricated with high purity and crystallinity.
针对反应体系Cu_(2+)−Ni_(2+)−NH_(3)−NH_(4)+−C_(2)O_(4)^(2-)−H_(2)O中Cu^(2+)和Ni^(2+)的反应行为,根据物质守恒原理,建立热力学数学模型。模拟计算结果表明,该体系中金属离子的沉淀是一个复杂的动态平衡过程;在高pH条件下,Cu^(2+)和Ni^(2+)与NH3配合分别形成[Cu(NH3)n]^(2+)(n=3−5)和[Ni(NH3)m]^(2+)(m=3−6)的反应占主导地位。当[C_(2)O_(4)^(2-)]T=0.6 mol/L时,Cu^(2+)和Ni^(2+)的共沉淀pH范围在[NH3]T为0.6 mol/L和4.2 mol/L时分别为2.0−6.5和2.0−5.5。在pH>7.0的纯水体系中,由于Cu^(2+)和Ni^(2+)的分步沉淀,Cu−Ni草酸复盐热分解后得到的产物为Cu−Ni复合物。改变沉淀介质为混合溶剂(水/乙醇)可最终制备具有高纯度和良好结晶度的棒状Cu−Ni合金粉末。
基金
the financial supports from Natural Science Foundation of Hunan Province,China(No.2020JJ4735)
Science and Technology Department of Hunan Province Tackling Key Scientific and Technological Problems and Transformation of Major Scientific and Technological Achievements,China(No.2018GK4001)
the Hunan Key Laboratory for Rare Earth Functional Materials,China(No.2017TP1031).
