Use of Sodium Hexametaphosphate and Citric Acid Mixture as Depressant in the Flotation Separation of Scheelite from Calcite

Abstract

The floatability of scheelite and calcite in the presence of single depressant (SHMP or H 3 Cit) and mixed depressant (SHMP/H 3 Cit) was studied by microflotation experiments and artificial mixed mineral experiments. Solution chemical calculation, zeta potential tests, thermodynamic analysis and XPS analysis were used to explain the relevant depressive mechanism. Mixed depressant (SHMP/H 3 Cit) exhibited excellent selective depressive effect on calcite. The optimal molar ratio of SHMP to H 3 Cit was 1:4. The depressant SHMP and H 3 Cit can be chemically bonded with Ca 2+ to form CaHPO 4 and Ca 3 (Cit) 2 at pH 8. The CaHPO 4 was more easily formed than Ca 3 (Cit) 2 on the mineral surface, which indicated that the depressive effect of SHMP was stronger than H 3 Cit. The SHMP and H 3 Cit of the mixed depressant were co-adsorbed on the calcite surface, while the H 3 Cit of the mixed depressant was weakly adsorbed on the scheelite surface. The mixed depressant can significantly improve the separation efficiency of scheelite from calcite. Sodium silicate (water glass) has been widely used as a depressant in flotation of scheelite from calcite [23]. However, sodium silicate also has some disadvantages as a depressant, such as frequent acidification, narrow optimum pH range, and weak selectivity. Single phosphates are also used for calcite depressants, but they are often limited by their weak selectivity, so mixed reagents are often required [24]. Organic macromolecular depressants have also received attention. Zhang et al. studied the role of sodium polyacrylate in flotation separation of scheelite and calcite [25]. However, sodium polyacrylate also has an unfavorable inhibitory effect on scheelite over a wide range of pH conditions, with poor flotation selectivity. Carboxymethyl cellulose has also been studied as a depressant in the flotation separation of scheelite from calcite [26], but it is difficult to dissolve carboxymethyl cellulose at room temperature, which is not conducive to flotation. In view of the shortcomings of the above single depressants, such as poor collecting ability, weak selectivity, and large dosage, it is often necessary to use mixed depressant to achieve flotation separation between scheelite and gangue minerals.Sodium hexametaphosphate (SHMP) is a clean, non-toxic phosphate that is widely used in the food industry and the chemical industry [27,28]. It can be used as a chelating reagent for metal ions, an adhesive, and a swelling reagent [29,30]. It is also widely used in the mineral processing industry, especially in the floatation. SHMP is used as a dispersant and depressant of minerals in flotation [31][32][33][34][35]. In addition, SHMP can be used to depress calcite [24], but it also has a strong depressive effect on scheelite. Citric acid (H 3 Cit) is also a clean, non-toxic organic acid and is a tricarboxylic acid compound. It is mainly used in the food industry, chemical industry, textile industry, cosmetics and pharmaceutical industries [36][37][38]. Citric acid can be used as depress...

Laboratory Testing of Scheelite Flotation from Raw Ore in Sangdong Mine for Process Development

“…Tungsten has been one of the important metals, which is widely used in various industries such as alloys, electron, chemical engineering, etc. [1][2][3][4][5][6][7]. Not only does it have the highest melting point among metals, but it also shows particularly high physical properties including moduli of compression and elasticity, thermal creep resistance and electrical conductivity [1,3,4,8].…”

“…There are various types of tungsten minerals. Among them, scheelite (CaWO 4 ) is considered as an economically important mineral [2,[4][5][6][7]9,[11][12][13][14][15][16][17]. To be specific, scheelite is easily ground to fine particles during crushing and grinding processes due to its brittleness [1,18,19].…”

“…This characteristic can be one of the reasons why many researchers have conducted researches about froth flotation for the recovery of scheelite from tungsten ore [1,19,20]. Froth flotation is an extensively used separation technique in the minerals industry that is based on differences in the surface properties of particles [1,5,7,11].…”

“…A fatty acid collector is extensively used in scheelite flotation from the raw ore during the process of separation [2,8,13,15,21]. Scheelite is often associated with other Ca-bearing salt-type minerals such as calcite and fluorite, which has similar characteristics [5][6][7]22,23]. Their dissolved mineral species in the pulp might be some reactions such as hydrolysis, precipitation and adsorption which can affect the interaction between reagents and minerals [5,24].…”

“…Scheelite is often associated with other Ca-bearing salt-type minerals such as calcite and fluorite, which has similar characteristics [5][6][7]22,23]. Their dissolved mineral species in the pulp might be some reactions such as hydrolysis, precipitation and adsorption which can affect the interaction between reagents and minerals [5,24]. Therefore, it is desirable to select suitable modifiers and depressants for selective separation which is available through the flotation method [5][6][7][8]12,16,21,24].…”