Guar Gum

Guar gum (GG) (Fig. 4.1) is a naturally derived nonionic polysaccharide with an average molecular weight between 100,000 and 2,000,000. The molecule of GG consists of 1–4 linked β-d-Mannopyranose components with α-d-Galactopyranose components randomly attached to the core mannose chain via 1 to 6 glycosidic linkages. The mannose-to-galactose ratio is between 1.8 to 1.0 (Painter et al. in Carbohydr Res 69:217–226, 1979; Whistler and Hymowitz, in Guar: agronomy, production, industrial use, and nutrition. Purdue University Press, 1979). GG can significantly treat base metal ores and platinum group metal (PGM) ores, where an excessive amount of talc is present. Since talc possesses natural hydrophobicity, it can be a troublesome mineral in froth flotation (Wang et al. in Miner Eng 18:77–81, 2005). GG is used in flotation operations to selectively adsorb onto talc, making it hydrophilic and decreasing its inherent hydrophobicity (Garcia Vidal and Pawlik in Int J Miner Process 138:38–43, 2015). Every unit of the structure of GG consists of nine –OH groups. By using H-bonding on the surface of minerals, these –OH groups are accessible to the GG molecule for adsorption on the mineral surfaces (Wang et al. in Miner Eng 18:77–81, 2005). It has been demonstrated that GG can act as a depressant for a wide range of minerals, including chromite, talc, and potash, while satisfactory results have also been reported for sulfide minerals, including pyrite (Laskowski et al. in Int J Miner Process 84:59–68, 2007; Ma and Pawlik in J Colloid Interface Sci 298:609–614, 2006; Ma and Pawlik in J Colloid Interface Sci 313:440–448, 2007; Shortridge et al. in Int J Miner Process 59:215–224, 2000).