Evaluation of Sulfonate-Based Collectors with Different Hydrophobic Tails for Flotation of Fluorite

Renji Zheng,Huimin Gao,Zijie Ren,Yupeng Qian

doi:10.3390/min8020057

Abstract

This investigation aims to demonstrate the effects of hydrophobic tails on the affinity and relevant flotation response of sulfonate-based collectors for fluorite. For this purpose, a series of alkyl sulfonates with different hydrophobic tails, namely sodium decanesulfonate (C10), sodium dodecylsulfate (C12), sodium hexadecanesulfonate (C16), and sodium dodecylbenzenesulfonate (C12B) were applied. The flotation tests showed that C12 and C12B had a better collecting performance than C10 and C16 at pH < 10, and the flotation recovery of fluorite was higher when adopting C12B as a collector compared with C12 with a strong base. The adsorption behaviors of collectors on the fluorite surface were studied through zeta potential, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. It was found that the affinity of alkyl sulfonates for fluorite was enhanced with the increase of the alkyl chain length from C10 to C16. The existence of phenyl in the hydrophobic tail of sulfonates could improve its activity for fluorite by reducing its surface tension. The abnormal phenomenon C16 with a high affinity for fluorite had a low collecting performance for fluorite mainly due to its overlong alkyl chain, resulting in low solubility in pulp, which restrained its interaction with fluorite. We concluded that C12B was the most applicable collector for fluorite among these reagents due to its high activity, high solubility, and low cost, which was further substantiated by calculating their molecular frontier orbital energy.

Highlights

Fluorite (CaF2 ), an important nonrenewable mineral that is primarily used for the manufacture of hydrofluoric acid, glass, cement, fillers, and as a flux regent in steel making, has in recent years been considered an important strategic mineral [1,2,3,4]
We investigated the flotation performance of fluorite that adopted sulfonate-based collectors with different hydrophobic tails
We found that hydrophobic tails played a significant role in determining the properties of surfactants, further affecting their collecting performance for fluorite during flotation experiments

Summary

Introduction

Fluorite (CaF2 ), an important nonrenewable mineral that is primarily used for the manufacture of hydrofluoric acid, glass, cement, fillers, and as a flux regent in steel making, has in recent years been considered an important strategic mineral [1,2,3,4]. Flotation has been regarded as one of the most commonly used techniques for separating fluorite from gangue minerals, employing fatty-acid collectors and sometimes associated with highly selective depressants [5,6]. It should be noted that the flotation separation of fluorite from calcium-bearing minerals is a very challenging task due the fact that their surface reactivity is similar to that of traditional fatty-acid collectors [7,8]. As fatty-acid collectors possess poor selectivity and low water-solubility at a low temperature, the separation is not always satisfactory on an industrial level without adding highly selective depressants. The previous study suggested the use of alkyl sulfonates as collectors, since they are more selective than fatty-acid salts [9]. The main active substance of the alkyl sulfonates collector is sulfonate, which has a highly hydrophilic sulfogroup connected with alkyl, giving rise

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Conclusion