Understanding limitations to monazite concentrate dissolution in oxalic acid

IF 4.8 2区材料科学 Q1 METALLURGY & METALLURGICAL ENGINEERING

Hydrometallurgy Pub Date : 2025-10-03 DOI:10.1016/j.hydromet.2025.106582

Mark Stephen Henderson, Laurence Gerald Dyer, Bogale Tadesse

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引用次数: 0

Abstract

Prior works with organic acids have shown dissolution of rare earth element (REE) bearing phosphate minerals with oxalic acid, solubilising phosphate and depositing rare earth oxalates that can be solubilised in a second stage. Previously published information shows local maxima in recovery and hypothesised reaction control mechanisms. The current article investigates reaction limitations (mineralogical and thermodynamic) in greater depth to inform process development.

Monazite concentrate was treated with oxalic acid at temperatures in a range from 30 °C to 95 °C. Various factors were found to influence the extent of phosphorus dissolution. Previous studies achieved <32 % phosphate dissolution at 65 °C, this work has demonstrated the ability to achieve in excess of 65 % conversion using a multi-stage, cross flow leach at 45 °C with a large reduction in simultaneous iron dissolution.

Approximately 65 % of the phosphorus was solubilised using a multi-stage, cross-flow leach system. Two different monazite compositional signatures, indicative of variations in REE and phosphorus contents, were identified displaying significantly different reactivity. One form readily dissolved in oxalic acid, the other experienced little or no reaction.

Calculated oxalate losses to the reprecipitated salts and complexation with solution components was used to estimate availability of free oxalate, this was supported by the concentration of elements with low oxalate solubility (Ca and Ce). It was demonstrated that free oxalate is a limiting factor in dissolution. It is therefore evident that under different conditions, there are both mineralogical and solution thermodynamic drivers for reaction rate and extent achievable.

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了解单氮石精矿在草酸中溶解的局限性

先前对有机酸的研究表明，含稀土元素（REE）的磷酸盐矿物与草酸溶解，溶解磷酸盐，并沉积可在第二阶段溶解的稀土草酸盐。先前发表的信息显示了恢复的局部最大值和假设的反应控制机制。本文更深入地研究了反应的局限性（矿物学和热力学），以便为工艺开发提供信息。用草酸在30 ~ 95℃的温度范围内处理独居石精矿。各种因素影响了磷的溶解程度。先前的研究在65°C下实现了32%的磷酸盐溶解，这项工作证明了在45°C下使用多级交叉流浸出可以实现超过65%的转化率，同时铁的溶解也大大减少。大约65%的磷是通过多级交叉流浸出系统溶解的。两种不同的独居石组成特征显示出明显不同的反应活性，表明稀土和磷含量的变化。一种形式很容易溶解在草酸中，另一种很少或没有反应。计算草酸盐在再沉淀盐中的损失和与溶液组分的络合作用被用来估计游离草酸盐的可用性，这得到了草酸盐溶解度低的元素（Ca和Ce）浓度的支持。结果表明，游离草酸盐是溶出的限制因素。由此可见，在不同条件下，矿物学和溶液热力学都是影响反应速率和可达到程度的驱动因素。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Hydrometallurgy 工程技术-冶金工程

CiteScore

9.50

自引率

6.40%

发文量

144

审稿时长

3.4 months

期刊介绍： Hydrometallurgy aims to compile studies on novel processes, process design, chemistry, modelling, control, economics and interfaces between unit operations, and to provide a forum for discussions on case histories and operational difficulties. Topics covered include: leaching of metal values by chemical reagents or bacterial action at ambient or elevated pressures and temperatures; separation of solids from leach liquors; removal of impurities and recovery of metal values by precipitation, ion exchange, solvent extraction, gaseous reduction, cementation, electro-winning and electro-refining; pre-treatment of ores by roasting or chemical treatments such as halogenation or reduction; recycling of reagents and treatment of effluents.