Outotec Oyj

Outotec (Finland) Oy

Jaakko Leppinen

Mikko Ruonala

Teppo Riihimäki

Olli Hyvärinen

Seppo Heimala

Heikki Takala

Liisa Haavanlammi

Matti Hämäläinen

Jari Moilanen

Jari Tiihonen

Ville Miettinen

Veikko Palosaari

Tuula Hämäläinen, Legal Representative

Teppo Riihimaki

A process for recovery of gold from gold-containing raw materials includes obtaining gold-containing raw material having refractory gold-containing sulfidic minerals including a first type of refractory sulfidic mineral having high gold content and a second type of sulfidic mineral having low gold content; forming a mineral pulp including a first type of refractory sulfidic mineral particles having high gold content and second type of sulfidic mineral particles having low gold content by suspending ground gold-containing material in water and optionally further milling the material; conditioning the mineral pulp by addition of a surface modifying chemical to obtain a conditioned pulp; subjecting the conditioned pulp to a froth flotation process; recovering the non-floatable first type of refractory sulfidic mineral particles having high cold content as flotation tailings; pressure oxidizing (POX) the flotation tailings to obtain a discharge slurry comprising liberated gold; and recovering gold from the discharge slurry.

Differential flotation of sulfide ores for recovering refractory gold

The invention relates to the hydrometallurgical treatment of laterite ores in order to recover valuable metals. More specifically, the invention presented relates to a method for improving precipitation and solid-liquid separation in conjunction with the leaching of laterite ores. According to the method the slurry exiting the leaching of laterite ores is neutralized, after which part of the slurry is routed to solid-liquid separation. Iron is precipitated from the solid-liquid separation overflow by neutralizing the solution and the solution that is formed, which includes jarosite seeds, is routed to an appropriate point in the process to control the precipitation of iron and to enhance the filterability of the solids.

Method for enhancing solid-liquid separation in conjunction with laterite leaching

The invention relates to a method for separating nickel and other valuable metals particularly from material having low nickel content, which contains iron and magnesium in addition to nickel and other valuable metals. The material having low nickel content is subjected to pulping and atmospheric leaching in acidic and oxidizing conditions, in which the majority of the metals in the material dissolve and the iron is partially precipitated. The precipitated iron is separated from the solution, after which nickel and the other dissolved valuable metals are precipitated as sulphides.

Method for separating nickel from material with low nickel content

The invention relates to a method for removing arsenic as scorodite from solutions that contain iron and arsenic. In accordance with the method, arsenic is first precipitated as ferric arsenate and subsequently processed hydrothermally into crystalline scorodite.

Method for removing arsenic as scorodite

The invention relates to a method for recovering gold from a sulphidic concentrate, particularly one containing arsenopyrite and/or pyrite, hydro-metallurgically. The concentrate is first subjected to leaching with a concentrated solution of alkali chloride and copper (II) chloride, by means of which the copper minerals and some of the gold in the concentrate are made to dissolve. Elemental sulphur and precipitated iron and arsenic compounds are separated from the leaching residue using physical separation methods, whereby the first intermediate is obtained, which contains gold-bearing sulphide minerals and gangue minerals as well as the gold that remains undissolved. The free gold that remains undissolved is separated by means of gravity separation methods. After gravity separation, additional comminution is carried out, after which the sulphide minerals are decomposed and the gold-containing solution or residue is routed to the concentrate leaching circuit.

Method for the recovery of gold from sulphide concentrate

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Espoo, Finland

Jaakko Leppinen