Abstract
The theory of using dilute organic acid solutions to leach the carbonaceous part from low-grade carbonaceous phosphate ore has been proposed by researchers as an effective approach to increase the proportion of P and to utilize the abundant low-grade resource. In this paper, a comprehensive experimental study was carried out to confirm the feasibility of organic acid leaching and investigate the optimized leaching conditions. Utilizing the low-grade carbonaceous phosphate ore produced in Zhijin, southwest of China, the effects of different types of acid, acid concentrations, reaction temperatures, reaction times, and liquid-solid ratios on leaching rate of P2O5 were evaluated using single-factor experiments and orthogonal experiments. The reaction mechanism, examined by SEM technique and the reaction thermodynamic analysis suggested that the leaching of P2O5 mainly resulted from the process of dissolution of dolomite (the main gangue mineral) in organic acid, consequently enriching the phosphate rock (the mineral of value). The effectiveness and impacts of different types of acid and reaction conditions were also studied. To conclude, this study first confirmed the viability of enriching P2O5 from low-grade ores through organic acid leaching the carbonaceous part by experimental data, and the experimental results will provide an essential scientific support for further upgrade of the technology to commercial scale utilization.
Highlights
The phosphate resources in China are abundant, they mainly consist of low-grade phosphate rock. e beneficiation of low-grade phosphate ores is a worldwide problem, and effective technologies to process such ores are yet to be developed
E main operating parameters of dilute organic acid leaching are organic acid concentration, reaction temperature, and reaction time. e effect of stirring intensity on leaching was not so significant that it was not investigated in this study [21]. e stirring intensity was fixed at 300 rpm to ensure no sediment at the bottom of beaker. e parameter of liquid-solid ratio is tested by a single-factor experiment
All three organic acids can improve the grade of P2O5, from the low level, which is 12% to 25%, to the higher level, which is above 30%
Summary
The phosphate resources in China are abundant, they mainly consist of low-grade phosphate rock. e beneficiation of low-grade phosphate ores is a worldwide problem, and effective technologies to process such ores are yet to be developed. Low-grade phosphate rock exploitation has become one of the main topics in mineral research, with emphasis on developing a cheap and environmentally friendly method to take full advantage of such phosphate resources [1, 2]. In China, most of the low-grade phosphate mines obtain phosphorus concentrate through the beneficiation process to proceed follow-up production, and a few of them are used to produce phosphate rock powder as fertilizer after activation (Li et al, 2015) [3,4,5]. In the process of phosphorus enrichment, the low-grade phosphate ore is often calcined by a type of thermochemical beneficiation process, or leached by a Journal of Analytical Methods in Chemistry strong acid such as sulfuric acid, hydrochloric acid, or phosphoric acid [9]. The current methods are not very economically efficient and environmentally friendly
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