Influence and mechanism of xanthan gum on the aggregation and flotation behavior of talc, olivine, and serpentine

Abstract

Finding appropriate flotation reagents to separate copper-nickel sulfide ores from various magnesium silicate gangue minerals has always been a challenge in the mineral processing industry. This study introduced xanthan gum (XG) as a non-toxic and environmentally friendly depressant of talc, olivine, and serpentine. The effects and mechanisms of XG on the aggregation and flotation behavior of talc, olivine and serpentine were investigated by flotation tests, sedimentation tests, IC-FBRM particle size analysis tests, adsorption quantity tests, Fourier transform infrared spectroscopy (FTIR) tests, X-ray photoelectron spectroscopy (XPS) analysis tests and Zeta potential tests. The flotation results indicated that when the three minerals were mixed, XG caused the talc-serpentine aggregation in the solution to shift to olivine-serpentine aggregation, with the remaining XG adsorbing on talc to depress its flotation. In addition, combining XPS and zeta potential tests, the —OH (hydroxyl) groups in XG molecules preferentially adsorbed on Mg sites on the surface of olivine through chemical bonding. The surface potential of olivine significantly shifted to a more negative value, with the negative charge on the olivine surface far exceeding that on the talc surface. This resulted in an increased aggregation effect between positively charged serpentine and negatively charged olivine due to enhanced electrostatic forces.

1. Introduction

Nickel and copper, as strategic metal resources, hold indispensable positions in modern industrial systems [1, 2]. Nickel has a wide range of applications across several industrial sectors, including stainless steel production, catalytic manufacturing, battery technology, electronic components, and aerospace engineering [3 −6]. Copper, known for its exceptional electrical conductivity, serves as a fundamental material in electrical engineering, power transmission infrastructure, electronic devices, architectural applications, and medical equipment [7 −10]. At present, copper-nickel minerals are mainly derived from sulfide deposits, which are usually accompanied by magnesium silicate minerals (MgO), posing a great challenge to the mineral separation process [11 −13]. Therefore, achieving efficient separation between target minerals and magnesium silicate minerals has become a key focus of mineral processing research. Currently, flotation process is the main technology to realize mineral separation.

In contrast to the research on collectors for target minerals, greater emphasis has been placed on the development and application of depressants. For instance, polysaccharide-based polymers, such as sodium alginate and sodium phytate, have demonstrated effectiveness in separating talc from copper-nickel sulfide ores [14, 15]. Additionally, novel phosphate-based reagents have been employed for the separation of serpentine from copper-nickel sulfide ores. Furthermore, the combination of acidified water glass and acacia gum has shown promise in separating magnesium silicate gangue minerals from refractory copper sulfide ores [16]. Previous studies have primarily focused on the separation of target minerals from single MgO-bearing gangue minerals, with limited research addressing the separation from multiple MgO-bearing gangue species. However, talc, serpentine, and olivine often coexist with copper-nickel sulfide ores and adversely affect the grade of target minerals through different mechanisms [17 −20]. Consequently, achieving efficient separation of copper-nickel sulfide ores from MgO-bearing minerals without the addition of flotation reagents remains a significant challenge.

Xanthan gum (XG) is a high molecular weight anionic polysaccharide with excellent biocompatibility, water solubility, cost-effectiveness and biodegradability [21]. Therefore, it has been widely used in the food industry, cosmetics and pharmaceutical industries [22, 23]. As shown in Figure 1, XG contains a large number of hydrophilic hydroxyl and carboxyl groups [24]. These groups can chelate with certain metals on the mineral surface, depressing the flotation process.