Minerals F_.nfineerin8, Vol. 6, No. 12, pp. 1265-1277, 1993 0892-6875/93 $6.00+0.00 Printed in Great Britain © 1993 Pergamon Press Lid ARSENOPYRITE ENRICHMENT BY COLUMN FLOTATION P. MAVROS, K.A. KYDROS and K.A. MATIS Department of Chemistry, Aristotle University, GR-540 06 Thessaloniki, Greece (Received 4 February 1993; accepted 2 July 1993) ABSTRACT Arsenic-rich, gold-bearing pyrite concentrates may befurther enriched in arsenic W assist subsequent Au beneficiation. Among several amines tested in refloating a local Chalkidiki pyrite concentrate, 2-coco 2-methyl ammonium chloride proved successful by raising the grade from 9% to 22%, although total solids recovery was low. The use of a froth- stabilizing frother was also beneficial to the process. Optimum hydrodynamic conditions were : intermediate pulp fiowrate, low wash water and gas flowrate; the latter abated the mixing~dispersion process in the collection zone. Keywords Column flotation; arsenopyrite; amines INTRODUCTION Pyrite concentrates sometimes contain considerable amounts of arsenic. Since they are usually used for the production of sulphuric acid, this is undesirable. However, gold is often associated with arsenopyrite, often exhibiting a direct relationship between Au content and As grade [1]. There is, therefore, some scope for concentrating arsenopyrite, since the ore itself is otherwise of little value. Previous work on pyrites has usually concentrated on the problem of floating pyrite. Xanthates are the most common collectors; these are used in conjunction with some arsenic-depressing reagent, e.g. KMnO 4, H202, NaOCI, among others [2] - at a limited dosage, otherwise pyrite is depressed, too. Other collectors are used, too, e.g. mercaptobenzothiazole [3] or dithiophosphates [4]. Arsenopyrite itself may be floated using a variety of reagents, e.g. dithiophosphates and dithiocarbamates [5], sodium dodecyl sulphonate [6] and other cationic collectors [7]. It was also found, through electrophoretic studies, that ferric iron (Fe 3+) ions confer a positive surface charge to pyrite particles; in contrast, arsenopyrite remains negative. This surface alteration becomes important in the acidic region around pH 4. Cetyl-trimethyl ammonium bromide has also been used as collector at acidic pH values, with ferric iron added to the dispersion [7]; it proved effective in raising - albeit moderately, from 7.5% to 14% - the arsenic content of the concentrate. The presence of xanthates, however, may cause problems in the subsequent cyanidation of pyrites when recovering their Au value [3,8]; this justifies the need to find alternative collectors. In a previous study with Cu, Zn and Pb sulphides [9], a Cl2-arnine acetate collector was compared to two common xanthate collectors - potassium amyl (KAX) and potassium ethyl (KEX) xanthate. The experimental results indicated that the amine exhibited a behaviour similar to that of the xanthates, with galena requiring a higher dosage of some frother and the use of an activator, prior to flotation by the amine. The benefit of the amine was in its lower consumption, as compared to the xanthate systems. M~ ~12--E 1265