Starch is mainly used for reverse flotation beneficiation process of oxidation of iron ore, iron oxide inhibition, the starch is most important use in dressing. Further, also when molybdenum sulfide flotation separation process such as copper, bauxite using reverse flotation. Processed starch can also selectively inhibit gangue minerals such as quartz , silicate and talc . The effects and inhibitory effects of different components of starch are different, mainly the effects of amylose and amylopectin content.
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S? Pavlovic et al. studied the inhibition of hematite and quartz by corn starch, its polysaccharide components (amylose and amylopectin), monomeric glucose and two-molecular polymer maltose. The results showed that the inhibitory effects of starch, amylose and amylopectin on hematite were very similar, and all of them could effectively maintain the hydrophilic properties of hematite. However, the inhibition effect on quartz is different. Amylose has the worst inhibitory effect on quartz, and only a flocculation effect (mainly produced by amylopectin) produced by the use of amine-based collectors is weak in reducing the floatability of quartz. The role.
The literature has examined in detail the selective flocculation of ultrafine iron minerals by branched and amylose. Amylopectin can flocculate most iron ore and high-purity hematite, while amylose does not flocculate any mineral. When used in combination, amylose inhibits amylopectin flocculation of iron ore, but slightly enhances the flocculation selectivity of amylopectin to hematite.
Wu Yongyun et al. tested the adsorption capacity of different starches on quartz and hematite as the pH value changed from small to large, and the adsorption amount decreased in the following order:
Cationic starch > Ordinary starch > Anionic starch
With the increase of pH, the adsorption amount of cationic starch on quartz and hematite increased; while the adsorption amount of anionic starch, common starch and dextrin decreased with the increase of pH value. The adsorption amount of cationic starch on the surface of quartz (between pH 7 and 11) is always higher than that on hematite. Anionic starch is the opposite. Therefore, starch has long been used as an inhibitor of certain ore flotation. Unmodified corn starch, anionic starch and dextrin in the reverse flotation process of hematite, whether it is the reverse flotation of fatty acids of Ca2+, Mg2+ activated quartz, or the reverse flotation of quartz amine collectors, the above starch They are effective inhibitors of hematite, imaginary hematite, and iron hydroxide. In the reverse flotation process of iron ore, cationic starch is more effective in inhibiting quartz than hematite because it preferentially adsorbs on the surface of quartz. Therefore, cationic starch cannot act as an inhibitor in the reverse flotation of iron ore.
Starch minerals belong to various rare metals exhibit different rejection: the concentration is not high, pyrochlore suppressed, pyroxene, and dolomite, fluorite inhibition in acidic, basic can occur, and Dolomite does not inhibit in acidic media.
It also exhibits different inhibitory properties for various salt minerals: when the oxidized ore such as calcite , barite , fluorite and other oxidized ore are separated and floated by oleic acid in an alkaline medium, the order of inhibition of starch: calcite > barite > Fluorite. Depending on the size of the inhibitory capacity, we can selectively separate these minerals. For example, at pH 10 or so, when the concentration of oleic acid is 1×10-4 mol/L, caustic starch has a strong inhibitory effect on barite. The ability to inhibit fluorite is relatively weak and separation can be achieved.
The starch is hydrolyzed to obtain a dextrin which is a relatively small molecular weight and water-soluble product. It is a non-ionic inhibitor used primarily to inhibit naturally hydrophobic minerals such as talc, coal- copper ore [65]. It is also widely used in sulphide ore flotation. The inhibitory effect of dextrin is more selective than starch. For example, in alkaline media, oleic acid is used as a collector, dolomite, calcite, barite, etc. can be inhibited by dextrin, while flotation of fluorite is basically unaffected.
Formulated with polyacrylic acid (salt) and lignosulfonate as stabilizers, causticized starch inhibits pyrite-based gangue in sulfide ore. The relative content of metals in the concentrate after flotation separation can be increased by nearly 10 times. If no inhibitor is added, the content of concentrate metal after flotation separation is only increased by nearly 5 times.
Li Haipu of Central South University pointed out that under acidic conditions, the inhibition of diaspore is based on the anionic starch (hydroxamic acid starch), cationic starch and raw starch, which has activating effect on kaolinite, and in this order. Decrement.
In summary, starch-based inhibitors are used in industrial production to inhibit talc, mica , natural sulfur , carbonaceous gangue, sulfide minerals, and the like. In particular, the oxidized ore anti-flotation mentioned above as an inhibitor, the inhibitor of chalcopyrite in copper-molybdenum separation, and some non-metallic ore flotation act as inhibitors have been applied on a large scale.
In addition, starch can also be used as a flocculant, and starch is used as an iron ore selective flocculant in the flocculation of iron ore. Some people have added starch at low silicate content to help flocculation of goethite; corn starch and tapioca starch can be used as selective flocculant for Abaga iron ore, concentrate grade and recovery rate. All reported high. This technology has been used in recent years for the enrichment of fine-grained iron minerals and fine mud.
Development trend of modified starch
Modified starch began to appear at the end of the 19th century and has a history of more than 100 years. The research on chemically modified starch in China began in the 1980s and has made great progress. However, compared with European and American countries, there is still a big gap. For example, the product variety is small and mostly single modified, and the process is backward. In particular, there is little research on basic theory.
Due to its unique properties, chemically modified starches are becoming more widely used and used more and more. The future development trend is diversification and functional compounding. For example, in order to overcome the limitations of performance and application of single modified starch, the current chemically modified starch is developing towards composite modification and multi-modification.