Method for removing arsenic from materials containing same

A process for the removal of arsenic from copper concentrates and/or copper cement with an arsenic content higher than 0.5% by dry weight or copper concentrates and/or copper cement with a high content of arsenic and selenium, comprising:

• adding the copper concentrates and/or copper cement to a pressure reactor;
• adding an alkaline leaching solution of a strong base selected from sodium hydroxide and potassium hydroxide dissolved in water to the pressure reactor;
• adding an oxidizing gas to the pressure reactor;
• mixing the above components in the pressure reactor to obtain a homogenous pulp and subjecting it to a pressure lixiviation that is selective for arsenic, wherein operation conditions of the pressure lixiviation are:
• temperature between 100° C. and 220° C., residence time of the pulp within the pressure reactor between 30 and 150 minutes, quantity of the leaching solution in the case of NaOH between 1.87 and 45.0 kg NaOH/kg As contained in the pulp, and oxidizing gas overpressure between 0 and 100 psig, wherein the dissolution of copper present in the copper concentrates and/or copper cement during said pressure lixiviation is less than 0.05% of the total copper, the dissolution of gold present in the copper concentrates and/or copper cement is less than 4% of the total gold and the dissolution of silver present in the copper concentrates and/or copper cement is less than 0.4% of the total silver;
• subjecting the pulp obtained from the pressure lixiviation to a first solid-liquid separation step thereby separating a solid with low arsenic content and a liquor containing dissolved arsenic in its +5 oxidation state in the form of arsenate;
• subjecting the liquor with dissolved arsenic to a precipitation of the arsenic with a precipitating agent that provides cations selected from Ce3+, Fe3+, Mg2+, or a combination of Fe3+ and Ca2+, said precipitating agent being selected from cerium chloride, ferric sulfate, magnesium sulfate, or ferric sulfate with addition of lime milk;
• subjecting the product of the arsenic precipitation step to a second solid-liquid separation step, thereby obtaining a solid arsenic-containing product and an alkaline liquor free of arsenic.