Various methods are commonly used for the ore dressing of antimony, including hand-sorting, gravity separation, and flotation.
Hand-Sorting
Applicability: Hand-sorting is suitable for antimony ore chunks with particle sizes ranging from 28 to 150 mm.
Procedure: Antimony ore chunks obtained through hand-sorting, with an antimony content above 7%, can enter the smelting process to produce crude antimony. Despite being primitive and labor-intensive, hand-sorting often yields high-grade chunk antimony concentrates. It involves directly discarding a large amount of waste rock, improving the original ore grade, effectively reducing ore dressing production costs, and is still widely applied.
Gravity Separation
Principle: Gravity separation exploits the large density and coarse particle characteristics of antimony ore for separation. Whether it is a single sulfide antimony ore or a sulfide-oxide mixed antimony ore, gravity separation can be used for sorting.
Advantages: Gravity separation can effectively sort a large amount of qualified coarse concentrate within a coarse particle size range. It requires less investment and is still a method favored by many ore dressing plants.
Flotation
Usage: Flotation is a commonly used method for antimony ore dressing and is suitable for various ore types, including sulfide antimony ore, sulfide-oxide mixed antimony ore, stibnite, tungsten-antimony gold polymetallic sulfide ore, antimony-arsenic gold sulfide ore, tin-lead-antimony-zinc polymetallic sulfide ore, antimony-lead-zinc-mercury polymetallic sulfide ore, and arsenic-antimony gold polymetallic sulfide ore.
Challenges: Although each of the three methods mentioned above has its advantages, for complex compositions of antimony ore, it is challenging for a single ore dressing method to achieve qualified grades and expected recovery rates. Therefore, a combined ore dressing method, such as gravity-flotation combination, may be employed.
Current Challenges: Flotation of antimony oxide ore remains a challenging issue, requiring further research, especially in the development of flotation reagents. Although some progress has been made, the resource recovery and utilization rate of antimony oxide ore are still very low.
Currently, there are two main methods for antimony smelting: wet smelting and pyrometallurgical smelting.
Wet Smelting
Alkaline Wet Smelting:
This method involves antimony leaching and electrolysis or oxidation-precipitation. Antimony is dissolved in the solvent during leaching, and the resulting solution is either electrolyzed to produce metallic antimony or subjected to oxidation-precipitation to yield sodium antimonate.
The leaching agent used in alkaline wet smelting is mainly a mixed solution of sodium sulfide and caustic soda. Electrodeposition of sodium thioantimonate solution can be membrane-electrodeposition or non-membrane electrodeposition. The cathode antimony obtained by electrodeposition has good quality, low impurity content, and is easy to refine into primary products.
Acidic Wet Smelting:
Acidic solvents are used for leaching in this method. Due to the harmful gas hydrogen sulfide produced when hydrochloric acid is used as a solvent, many patents propose using ferric chloride as a leaching agent. Some patents also use antimony pentachloride as a leaching agent. The solution obtained from leaching with antimony trichloride is subjected to membrane electrolysis or iron replacement to produce metallic antimony or antimony trioxide.
Pyrometallurgical Smelting
Volatilization Roasting-Reduction Melting:
This method is commonly used for the treatment of chunky single sulfide antimony ore with a grade of 10%~18%. It involves using reverberatory furnaces or shaft furnaces for volatilization roasting. A chunky ore with an antimony content of 10%~20% and a mixture of heavy ore dressing and flotation concentrates are often subjected to conventional volatilization roasting. Flash volatilization roasting is used for sulfide antimony concentrates with an antimony content of 50%~60%. The roasting gas contains 8%~12% sulfur dioxide, which can be used to produce sulfuric acid.
Volatilization Smelting-Reduction Smelting:
Blast furnace volatilization smelting is usually used to process sulfide antimony ore containing 30%-50% antimony or mixed ores. It can also handle intermediate products of antimony smelting such as slag and crude antimony. When processing powder ore, it needs to be agglomerated or granulated first. This method has strong adaptability to raw materials. In addition to producing antimony trioxide, it also produces a small amount of crude antimony and antimony dross, which can enrich precious metals for easy recovery. The slag contains 0.8%-1.4% antimony, and the gas contains 0.3%-0.8% sulfur dioxide, which meets emission standards after treatment.
