Fenugreek Gum Study: Improved Flotation of High-Clay-Content Gold Ore Using Fenugreek Polysaccharide Gum as the Depressant
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https://www.mdpi.com/2075-163X/15/5/446
Excerpts from study:
“Abstract
Due to the influence of the clay minerals, the grade of the concentrate from a gold concentrator in Northwest China is low, which significantly compromises product valuation and market competitivenes. This study evaluated the industrial potential of fenugreek polysaccharide gum (FGM) as a depressant to enhance the flotation through pilot-scale testing. Results showed that the FGM system effectively upgraded the concentrate grade by 4.7 g/t, while slightly increasing recovery by 0.37%. The application of FGM has generated an additional $1.715 million profit over the past two years. These findings suggest that FGM holds significant potential for large-scale industrialization in the flotation of high-clay-content sulfide ores.”
Keywords:
hydrophobicity; depressant; industrial test; concentrate grade
“1. Introduction
A gold mine located in Qaidam Basin of China is low-grade (with an average Au grade of 2.3 g/t) and high-clay-content (with clay accounting for 28.5%), and its dominant gold-bearing mineral is arsenopyrite [1,2]. It pertains to typical refractory gold ore and frequently coexists with clay minerals like pyrophyllite and mica [3]. Pyrophyllite and mica, with low hardness (moss hardness of 1–2.5) and good natural floatability, usually generate a significant amount of slime during grinding. This slime may seriously interfere with the flotation of sulfide minerals and is easily transported to flotation concentrate, leading to a reduction in concentrate grade [4,5]. In the flotation process of this ore, it is challenging to effectively separate the main Au-carrier mineral arsenopyrite and the primary gangue mineral pyrophyllite and mica without adding any depressant.
The depression of clay minerals in flotation can be achieved using inorganic or organic reagents designed to suppress silicate minerals. Commonly used depressants include water glass, hexametaphosphate, fluorocompounds, carboxymethyl cellulose, guar gum and lignosulphonate [6,7,8,9,10]. Among these, guar gum and other polysaccharide polymers have been widely used for sulfide mineral flotation, but this tends to pose severe disadvantages such as price sensitivity to market conditions, limited availability and high cost [5,7,10]. Therefore, there is a pressing need to develop more selective, cost-effective and high-performance depressants for the separation of sulfide minerals from hydrophobic clay minerals.
Fenugreek polysaccharide gum (FGM) is extensively present in beans, bitter beans and other leguminous plants. It possesses excellent water solubility and emulsifying characteristics and can react with a variety of metals [11,12]. It is widely used in the fields of flotation, food industry and pharmaceutical industry [13,14,15]. In this study, the pilot plant tests were conducted to examine the industrial potential of FGM as a depressant for this specific gold ore in Qaidam Basin. Additionally, the economic benefits of industrial operation over the past two years were evaluated.
2. Materials and Methods
FGM used in this experiment came from Shandong Gukang Biotechnology Co., Ltd. (Jinan, China), which was a white powder with excellent water solubility. In both the pilot plant test and industrial production, sodium carbonate (Na2CO3) was used as the pH regulator, cupric sulfate (CuSO4) as the activator, sodium isobutyl xanthate (SIBX) and ammonium dibutyl dithiophosphate (ADD) as mixed collectors and pine oil as the frother. All other reagents and dosages remained constant during the trials while only the FGM depressant was added compared with the old flowchart.
Based on the lab closed-circuit flotation tests, a pilot-scale test (as Figure 1) was carried out at a gold concentrator in Northwest China. The raw ore, concentrate and tailings were sampled, filtered, dried and weighed. Subsequently, the gold grade of the sample was assayed, and the recovery was calculated.”
“4. Conclusions
The novel green depressant FGM (featured by inherent biocompatibility and biodegradability) demonstrated exceptional performance in enhancing flotation efficiency for refractory gold ores characterized by low grade and elevated clay content. Key findings reveal its significant potential for industrial-scale applications:
(1) Process optimization: FGM achieved a notable 4.7 g/t increase in concentrate grade while maintaining recovery rates (+0.37%) compared to conventional reagents, particularly effective in managing clay interference during separation.
(2) Economic validation: industrial implementation yielded an additional $1.715 million in profits over a two-year operational period, substantiating both technical efficacy and economic viability for mineral processing operations.
(3) The selective adsorption of FGM on gangue mineral (muscovite) and valuable mineral (pyrite) causes the selective depression of muscovite.
(4) Implementation considerations:
Operational stability: while promising, the reagent’s long-term performance consistency requires extended validation under continuous production conditions.
Mineralogical sensitivity: effectiveness appears ore-specific, showing variable responses to different clay types and content levels, necessitating tailored optimization strategies based on ore composition.”
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