Surface Mechanism of Fe3+ Ions on the Improvement of Fine Monazite Flotation With Octyl Hydroxamate as the Collector.

Qingzhu Zheng,Zhen Wang,Haidong Dai,Yang Bai,Yunlou Qian,Dan Zou

doi:10.3389/fchem.2021.700347

Abstract

Froth flotation of fine minerals has always been an important research direction in terms of theory and practice. In this paper, the effect and mechanism of Fe3+ on improving surface hydrophobicity and flotation of fine monazite using sodium octyl hydroxamate (SOH) as a collector were investigated through a series of laboratory tests and detection measurements including microflotation, fluorescence spectrum, zeta potential, and X-ray photoelectron spectroscopy (XPS). Flotation tests have shown that fine monazite particles (−26 + 15 μm) cannot be floated well with the SOH collector compared to the coarse fraction (−74 + 38 μm). However, adding a small amount of Fe3+ to the pulp before SOH can significantly improve the flotation of fine monazite. This is because the addition of Fe3+ promotes the adsorption of SOH and greatly improves the hydrophobicity of the monazite surface. This can result in the formation of a more uniform and dense hydrophobic adsorption layer, as shown by the fluorescence spectrum and zeta potential results. From the XPS results, Fe3+ reacts with surface O atoms on the surface of monazite to form a monazite–Osurf–Fe group that acts as a new additional active site for SOH adsorption. A schematic model was also proposed to explain the mechanism of Fe3+ for improving surface hydrophobicity and flotation of fine monazite using octyl hydroxamate as a collector. The innovative point of this study is using a simple reagent scheme to float fine mineral particles rather than traditional complex processes.

Highlights

Rare earth metals are an important input to the development and manufacture of many green and high-tech products
In order to determine the flotation response of monazite particles (−26 + 15 μm) with or without the addition of Fe3+, and the difference in the flotation behavior compared with the coarser (−74 + 38 μm) ones, microflotation tests were conducted with 2 × 10−4 M sodium octyl hydroxamate (SOH) as the collector
The effect of pH on mineral recovery is due to the low degree of dissociation of SOH to SO− in a low pH range, the active constituent to adsorb on the monazite surface, and the formation of hydrophilic metal hydroxide on the monazite surface in a high pH range

Summary

Introduction

Rare earth metals are an important input to the development and manufacture of many green and high-tech products. Rare earth elements (REEs) have important strategic value and are called “the mother of new materials’’ (Jordens et al, 2013). There is still little value in mining the world’s rare earth deposits, and only a few deposits from China and the United States are doing large-scale mining. The ore types of these deposits are the main bastnaesite and monazite (Mancheri et al, 2019). Monazite [REPO4] mineral belongs to the monoclinic system and is one of the important minerals of mixed light rare earth resources in northern China (Yang et al, 2007). Flotation is the most effective way to concentrate monazite from related gangue minerals compared to the combined gravity–magnetic–electrostatic enrichment process

Methods

Results

Conclusion