Acid curing and agglomeration for heap leaching

- Agglomeration occurred with the addition of suitable amounts of water and acid.
- Copper extraction was significantly improved after the acid curing.
- Cu, Fe, etc. were dissolved and enriched in the fine fraction of the ore during acid curing.
- Each mineral behaved differently during acid, which was dependent on its own property.

The impact of acid treatment in agglomeration/acid curing on copper extraction and acid consumption was investigated with respect to acid dosage and moisture. Without the addition of water, no agglomeration occurred. At an acid dosage above 15 kg/t, the acid was not completely consumed during acid curing. With the addition of a suitable amount of water, the particles well agglomerated together. Copper, iron, magnesium and manganese were dissolved as sulfates and concentrated in the fine fraction of the ore. The copper extraction and net acid consumption increased with increasing acid dosage. The copper extraction for acid curing with the addition of 6.2% water was higher than that without the addition of water due to the improved permeability of a heap and the increase in the water-soluble copper. During acid curing, the reaction of sulfuric acid with muscovite, albite and nacrite mainly took place on the surface of the particles while the reaction of sulfuric acid with clinochlore occurred not only on the surface but also through the particles. This work contributes a case study to the body of knowledge on curing/agglomeration, which is currently relying essentially on empirical trial-and-error adjustment of conditions in practice. Further investigation is needed to develop fundamental understanding of acid curing and agglomeration for better operating practice.