Zinc leaching residue is considered as hazardous solid waste from zinc leaching process. Apart from zinc, it may also contains lead, indium and precious metal, which are of great value to recover. On the other hand, required by the government’s environment regulation, the leaching residue has to be treated for bio-safety disposal.

Categorized by its leaching process, the leaching residue has different content, which plays a decisive role in taking treatment methods for metal recovery.

In conventional leaching, zinc leaching rate is about 80%. So, the leaching residue usually consists of zinc about 18-20%, iron 20%, lead 5%, copper 1.5% and the balance gangue. Generally, it is treated by Waelz Kiln to have zinc and lead volatized and collected as zinc oxide and lead oxide, which further goes to electrical arc furnace to recover lead and zinc.

As for high acid leaching, the leaching rate is high as 97% and most of the iron dissolves in the acid and then separated by iron precipitation. In this case, leaching residue contains about zinc 4-6%, iron 6-10%, and the balance lead, silver, valuable metals and elemental sulfur. Several treatment methods of this high acid leaching residue are applied.  

 

Metalcess provides leaching residue treatment solution with two oxygen-enriched side-blowing furnaces for smelting and fuming respectively. Lead and valuable metal are enriched into lead bullion or copper matte for further recovery and zinc is fumed into zinc vapor and collected as zinc oxide powder. Both furnaces apply oxygen-enriched air and use crushed coal as fuel and reduction agent. This solution separate lead and zinc to avoid lead being locked in the circle, of high ROI. The process is adjustable to different capacity level.