REMOVAL OF ARSENIC IN ENARGITE FROM COPPER ORES BY FLOTATION AND LEACHING IN NAHS MEDIA

摘要

Removal of arsenic (As) contained as enargite (Cu_3AsS_4) in copper ores and concentrates by flotationrnand leaching was performed in this work. Flotation was first conducted to separate Cu_3AsS_4 fromrnother non-arsenic bearing copper–iron sulfides and other gangue to reduce As content to <0.5 wtrnper cent. The Cu_3AsS_4 fraction recovered as separate Cu concentrate is further treated by selectivelyrnleaching As in NaHS–NaOH solution for conversion to Cu2S and combine with clean concentrate inrnthe flotation process for feed to smelters. Direct leaching of Cu_3AsS_4 ore and mixture of Cu_3AsS_4 andrnother copper concentrates with low As content was also investigated.rnIn flotation, slurry pH and potential, reagent concentration, residence time, were investigated asrnmain parameters to evaluate separation efficiency of Cu_3AsS_4 from pyrite (FeS_2) and chalcopyritern(CuFeS_2). Results showed that >98 per cent of Cu_3AsS_4 can be separated from FeS_2 and CuFeS_2rnminerals at pH 4 within 5 min and As content in tailings or other sulfides reduced to <0.5 wt per cent.rnLeaching of enargite ore, concentrate or mixtures containing Cu_3AsS_4 with As content ranging fromrn0.8 - 10 wt per cent at varying conditions of temperature, pulp density, NaHS/NaOH conconcention,rnparticle size, slurry stirring rate and reaction time have been investigated to evaluate As leaching.rnThe results clearly show that >99 per cent of As in the samples can be selectively dissolved intornsolution with Cu_3AsS_4 transformed to Cu2S and As content in the leached residue reduced to <0.5 wtrnper cent. Leaching tests at pulp densities ranging from 100 - 1000 g/L showed that near completernremoval of As can be achieved within 3 - 6 h depending on pulp density and arsenic content. Atrn1000 g/L >98 per cent of As was removed within 6h at 80℃. Flotation and leaching conditions tornachieve separation and high As removal from Cu_3AsS_4 is discussed in this paper.