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Roasting of copper concentrates represent a major source of enviromental contamination. When copper sulfides are roasted poisonous SO2 ( sulphur dioxide) gases are produced, and in many operations of this type in the world these gases are not treated but released to the atmosphere as such. The transformation of these gases into sulphuric acid is expensive and the world produces already too much sulphuric acid. In this study we have found that roasting copper sulfides concentrates with ammonium sulphate produces a sublimate of ammonium sulphide that can be treated to regenerate the reagent ammonium sulphate to treat more concentrates. The gas produced in this second operation- hydrogen sulphide-can be reduce to elemental sulphur or washed with an alkali, as sodium hydroxide or calcium hydroxide-to render it as a solid compound.

• Ammoniacal Roasting

Concentrate	1000,00	/tm		Sublimate
Reaction Nr.1	CuS+	(NH4)2SO4=	CuSO4+	(NH4)2S
Weight	95,54	132,00	159,54	68,00
Actual weight	1000,00	1381,62	1669,88	711,74
Roasting
Decomposition temperature of (NH4)2SO4 : 537°C
Gas washing steps:
Reaction Nr.2	(NH4)2S+	H2SO4=	(NH4)2SO4+	H2S
Weight	68,00	98,00	132,00	34,00
Actual weight	711,74	1025,75	1381,62	355,87
Reaction Nr.3	H2S+	2NaOH=	Na2S+	2H2O
Weight	34,00	80,00	78,00	36,00
Actual weight	355,87	837,35	816,41	376,81

Authors' Reference:

Adolfo Rios Pita Giurfa, Peruvian, has developed several hydrometalurgy processes, among these: a method for ecological & cheap recycling of aluminium metal; a method for recovering lead as lead sulphate- pigment grade- out of the Lead-silver residues of zinc refineries; a method for recovering mercury and selenium from zinc roast dust flues,etc. In recent years was hired by Minero-Peru for the construction of a plant for the production of C.P.Cadmium pigments.

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