ITOS SILVER - ORURO BOLIVIA                            

     applying modern technology

    in a land of rich natural resources





This page shows photographs of Leaching and Precipitation  Sections.

The page "Photos General" shows the setting of the Itos plant, the tailings and ore microscope photos of the ore.  The page "Refinery Photos" shows the refinery section of the plant.

An aerial view of the Itos plant shows the feed tailings on the extreme left.  The large building in the center is the leach/ precipitation plant.  The refinery building is located to the left of the leach plant.  The white-colored installation to the extreme left is the hydrochloric acid plant.  The new tailings pond is located about 750 meters to the right.

The process begins by feeding the Itos tailings through a screen and into a tank where they are slurried to 50% solids with process solution.  From here the slurry is pumped about 500meters to the leach tanks.

The slurry is leached for 8 hours in agitated tanks at 75 degrees C. 

The leached slurry is filtered on three very large plate and frame filters, and the clear "pregnant solution" is pumped to the tanks in the back- ground.  The filter cake drops to the basement, where it is re-slurried and pumped to the new tailings pond.

Hot solution is cooled with cold water, and lead chloride is crystallized out.  This material is stored - we currently have about 1900 tonnes of lead worth $800,000 in storage. 

The lead-free solution is sent to an 8-ft dia- meter, 30 ft long precipitation drum where it is contacted with scrap iron.  A metal precipitate is formed containing the silver and other metals.  The precipitate is then collected and filtered in the filter shown in the center of the photo.

About two tonnes of precipitate are made each day, assaying 8% silver, 10% copper, 20% lead, 20% antimony, 2% iron, 2% arsenic.  The balance is fine particles of ore that escaped the filters.   

Approximately 3 tonnes per day of chlorine gas is used to provide the oxidant for leaching the ore.  It is received in one ton tanks, imported into Bolivia from Peru.  One of the new plant improvements underway at the time of the recent  shutdown was to replace chlorine oxidation with air oxidation resulting in a savings of $30,000 per month.  A pile of scrap iron - used in the precipitation drum - is shown in the foreground.   

Please go the "Refinery Photos" page to view the completion of the process.

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