Abstract

Ludwigite ore is a typical low-grade boron ore accounting for 58.5% boron resource of China, which is mainly composed of magnetite, lizardite and szaibelyite. During soda-ash roasting of ludwigite ore, the presence of lizardite hinders the selective activation of boron. In this work, lizardite and szaibelyite were prepared and their soda-ash roasting behaviors were investigated using thermogravimetric-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) analyses, in order to shed light on the soda-ash activation of boron within ludwigite ore. Thermodynamics of Na2CO3-MgSiO3-Mg2SiO4-Mg2B2O5 via FactSage show that the formation of Na2MgSiO4 was preferential for the reaction between Na2CO3 and MgSiO3/Mg2SiO4. While, regarding the reaction between Na2CO3 and Mg2B2O5, the formation of NaBO2 was foremost. Raising temperature was beneficial for the soda-ash roasting of lizardite and szaibelyite. At a temperature lower than the melting of sodium carbonate (851 °C), the soda-ash roasting of szaibelyite was faster than that of lizardite. Moreover, the melting of sodium carbonate accelerated the reaction between lizardite with sodium carbonate.

Highlights

  • Boron is widely used in glass, ceramic, abstergent and fertilizers, accounting for three-quarters of the global boron consumption annually, in which borax and boric acid are the most commonly traded commodities [1]

  • Ludwigite ore reserved in China is a typical low-grade boron ore, which is mainly composed of magnetite (Fe3 O4 ), lizardite (Mg3 Si2 O5 (OH)4 ) and szaibelyite (Mg2 B2 O4 (OH)2 ) [5,6]

  • The soda-ash roasting method has been proved to be an effective way for boron extraction from low-grade ludwigite ore, by improving the leaching activity of B2 O3 with the aid of sodium carbonate [13,14]

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Summary

Introduction

Boron is widely used in glass, ceramic, abstergent and fertilizers, accounting for three-quarters of the global boron consumption annually, in which borax and boric acid are the most commonly traded commodities [1]. Boron reserves in China are mainly ludwigite ore, which accounts for 58.5% boron resource [2]. As the increasing demand for boron resource, the effective utilization of the ludwigite ore is imperative to supply boron for China domestically. Ludwigite ore reserved in China (mainly in Liaoning and Jilin Provinces) is a typical low-grade boron ore, which is mainly composed of magnetite (Fe3 O4 ), lizardite (Mg3 Si2 O5 (OH)4 ) and szaibelyite (Mg2 B2 O4 (OH)2 ) [5,6]. The soda-ash roasting method has been proved to be an effective way for boron extraction from low-grade ludwigite ore, by improving the leaching activity of B2 O3 with the aid of sodium carbonate [13,14]. An alternative method for simultaneously recovering boron and iron has been proposed in our previous research, with the advantage of low-cost synthesis of sodium metaborate (NaBO2 ·2H2 O) and preparation of powdery DRI (direct reduction iron) [15]

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