Rheological properties and entrainment behavior of quartz/amorphous silica in chalcopyrite flotation
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摘要: 硅酸盐类脉石夹带是制约贫杂难选矿高效浮选分离的难题之一。借助分批浮选试验、流变学测试、冷冻扫描电镜测试、颗粒沉降试验，探究了黄铜矿浮选体系晶态/无定形二氧化硅的流变特性与夹带行为。结果显示，随着脉石中无定形二氧化硅含量的增加，矿浆表观黏度呈指数型增大，黄铜矿回收率持续降低，脉石回收率先升高后降低。脉石回收率发生变化是脉石夹带率、水回收率共同作用的结果：在黏度低增长区，脉石夹带率上移对脉石回收率升高起主导作用，而在黏度中、高增长区，水回收率减少是脉石回收率由升转降的主要原因。总脉石夹带率和各粒级脉石夹带率均随无定形二氧化硅含量增加而升高，且各粒级脉石夹带率呈现出明显差异性，细粒脉石夹带率增幅最大。冷冻扫描电镜与沉降试验表明，无定形二氧化硅与石英颗粒形成了聚集体结构，导致矿浆体系黏度增大，因而脉石颗粒沉降减缓、泡沫排液“洗涤”脉石作用弱化，单位泡沫水中的脉石质量增大，脉石夹带率升高。Abstract: Owing to the global consumption of high-grade ores, large amounts of low-grade and complex ores are being processed nowadays. The entrainment of gangue minerals in the ores, especially silicate gangue minerals, has become a nonignorable issue that can significantly influence mineral flotation performance. Amorphous silica has been reported to exist widely in various ore deposits, but how it affects mineral flotation remains poorly understood. This study investigated the rheological properties and entrainment behaviors of quartz/amorphous silica gangue in copper flotation through batch flotation tests, rheology measurements, cryo-SEM analysis, and particle settlement tests. Results indicate an exponential increase in the pulp viscosity as the amorphous silica content in the gangue increased. These also led to distinct recoveries of chalcopyrite and gangue minerals in flotation: the chalcopyrite recovery kept decreasing, whereas the entrainment recovery of gangue minerals increased initially and then decreased. The change in the entrained gangue recovery was found to be a consequence of the reduced water recovery and the increased degree of entrainment for the gangue. In a range wherein the viscosity growth was low, the increased degree of entrainment for the gangue prevailed over the decreased water recovery, ultimately leading to an increase in the gangue recovery. However, when the pulp viscosity drastically increased, the decreased water recovery was found to be dominant in changing the gangue recovery, and thus the gangue recovery decreased. Further, the effect of amorphous silica on the degree of entrainment for the gangue was investigated on a size-by-size basis. A great difference was found in the degree of entrainment for the gangue mineral particles of the same size fraction. However, fine gangue mineral particles experienced the greatest increase in their entrainment degree. Therefore, the degree of entrainment for the gangue was size-dependent and subject to the presence of amorphous silica. The results of cryo-SEM and settling tests indicate that quartz/amorphous silica particle aggregates were formed when amorphous silica particles were present in the flotation system, and these aggregates had a relatively low sedimentation rate. It was inferred that formed gangue aggregates increased the pulp viscosity, which reduced the water drainage in the froth and the sedimentation rate of gangue particles, subsequently increasing the mass of the gangue in a unit mass of water and, thus, the degree of entrainment.
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Key words:
- flotation /
- entrainment /
- amorphous silica /
- rheological property /
- degree of entrainment
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图 5 石英/无定形二氧化硅矿浆表观黏度（剪切速率为100 s−1）
Figure 5. Apparent viscosity of the quartz/amorphous silica pulps at a shear rate of 100 s−1
图 6 不同无定形二氧化硅含量下浮选脉石回收率与水回收率
Figure 6. Entrained gangue recoveries and water recoveries obtained from the flotation with different amorphous silica contents
图 7 脉石中无定形二氧化硅含量对水回收率的影响
Figure 7. Effect of the amorphous silica content in the gangue on water recovery
图 8 脉石中无定形二氧化硅含量对全粒级(a)和分粒级(b)夹带率的影响
Figure 8. Effect of the amorphous silica content in the gangue on the degree of entrainment on a unsized (a) and size-by-size (b) basis
图 10 石英/无定形二氧化硅悬浮液中颗粒形貌图. (a) 石英; (b) 石英/无定形二氧化硅质量比为4∶1; (c) 石英/无定形二氧化硅质量比为3∶2; (d) 石英/无定形二氧化硅质量比为2∶3; (e) 石英/无定形二氧化硅质量比为1∶4; (f) 无定形二氧化硅
Figure 10. Cryo-SEM images of the quartz/amorphous silica particles in the suspensions∶ (a) quartz; (b) mass ratio of quartz to amorphous silica at 4∶1; (c) mass ratio of quartz to amorphous silica at 3∶2; (d) mass ratio of quartz to amorphous silica at 2∶3; (e) mass ratio of quartz to amorphous silica at 1∶4; (f) amorphous silica
图 11 无定形二氧化硅改变脉石夹带率机理示意图
Figure 11. Schematic of the mechanism for the amorphous silica particles changing the degree of entrainment
图 12 脉石中无定形二氧化硅含量对精矿铜品位、产率和黄铜矿回收率的影响
Figure 12. Effects of the amorphous silica content in the gangue on concentrate copper grade, yield, and chalcopyrite recovery
表 1 浮选入料组成矿物
Table 1. Minerals used for the flotation feed
Sample name Purity/% Manufacturer Chalcopyrite 96 Hubei Daye Copper Mine Quartz 99 Yijing Quartz Sand Factory Amorphous silica 99 Aladdin Biochemical Technology 
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表 2 浮选试验药剂
Table 2. Reagents used in the flotation tests
Sample name Purity Manufacturer Sodium ethyl xanthate 90% Aladdin Biochemical Technology Co., Ltd. Methyl isobutyl carbinol Analytically pure Sinopharm Chemical Reagent Co., Ltd. Sodium carbonate Analytically pure Sinopharm Chemical Reagent Co., Ltd.
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