Classical hydrometallurgy methods such as chemical precipitation, ion exchange, solvent extraction and adsorption have been used to recover vanadium from aqueous solutions, but the last step of these methods involves precipitation with ammonium salts, which are harmful to the environment at high concentration. Therefore, here we tested urea as a new precipitant to replace ammonium salts. We studied the effect of various parameters on the precipitation efficiency of vanadium. Results showed that urea is hydrolyzed to form NH₄⁺ in acidic medium at 90 °C. Then, NH₄⁺ reacts with V₆O₁₆²⁻ and precipitates as (NH₄)₂V₆O₁₆. Nearly 95% of the vanadium was precipitated within 120 min in the system containing 2.8 g/L vanadium and n(CON₂H₄)/n(V) of 0.6. The Avrami model was used to describe crystallization kinetics and analysis of the dimensions of crystal growth. Model results show that the crystalline growth was one-dimensional and that the crystals were shaped in columns. Overall, this study introduced a new way for urea utilization as a new precipitant to recover vanadium.

中文翻译：

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在酸性介质中用尿素回收钒

经典的湿法冶金方法，例如化学沉淀，离子交换，溶剂萃取和吸附已用于从水溶液中回收钒，但是这些方法的最后一步涉及用铵盐沉淀，该铵盐在高浓度下对环境有害。因此，在这里我们测试了尿素作为替代铵盐的新型沉淀剂。我们研究了各种参数对钒沉淀效率的影响。结果表明，尿素在90°C的酸性介质中水解形成NH ₄ ⁺。然后，NH ₄ ⁺与V ₆ O ₁₆ ^2-反应，以（NH ₄）₂ V ₆ O的形式析出。₁₆。在含有2.8 g / L钒和n（CON ₂ H ₄）/ n（V）为0.6的系统中，在120分钟内将近95％的钒沉淀出来。Avrami模型用于描述结晶动力学和晶体生长尺寸的分析。模型结果表明，晶体生长是一维的，晶体呈圆柱状。总的来说，这项研究为尿素利用提供了一种新的方法，将其作为回收钒的新沉淀剂。