Using of leaching reactant obtained from mill scale in hydrometallurgical copper extraction

Area of Science:

• Metallurgical Engineering
• Environmental Science
• Materials Science

Background:

• Mill scale, a byproduct of the iron-steel industry, contains significant iron content.
• Chalcopyrite is a primary copper-bearing mineral requiring efficient extraction methods.
• Valorizing industrial waste streams like mill scale is crucial for sustainable resource management.

Purpose of the Study:

• To investigate the dissolution of iron from mill scale into an iron chloride solution using hydrochloric acid.
• To evaluate the efficacy of this iron chloride solution as an oxidizing leaching agent for copper extraction from chalcopyrite concentrate.
• To optimize the conditions for both mill scale iron dissolution and subsequent copper extraction.

Main Methods:

• Mill scale was leached with hydrochloric acid (HCl) under specific conditions (60 min, 105 °C, 7 M HCl, 1/10 solid-liquid ratio) to produce an iron chloride (FeClx) solution.
• The obtained FeClx solution was used to leach copper from chalcopyrite concentrate under optimized conditions (120 min, 105 °C, 1/25 solid-liquid ratio, 400 rpm).
• A simultaneous leaching process involving mill scale, chalcopyrite, and HCl was also conducted under optimized conditions.

Main Results:

• 100% iron solubility and 83.43% Fe3+ conversion were achieved during mill scale treatment.
• Optimal conditions for copper extraction using the mill scale-derived solution yielded 95.04% copper recovery.
• In a combined leaching process, approximately 96% of copper was extracted from chalcopyrite concentrate.

Conclusions:

• Iron from mill scale can be effectively dissolved in HCl to form a useful FeClx solution.
• This FeClx solution demonstrates high efficiency in extracting copper from chalcopyrite concentrate.
• The study highlights a viable method for waste valorization and efficient copper recovery from a valuable ore.