Auxiliary depression of copper ion - strengthening the depression of sodium trithiocarbonate on chalcopyrite

•► Copper ions can be used as auxiliary depressant for chalcopyrite depression.•► Na2CS3 can reduce adsorption capacity of BX on chalcopyrite surface.•► Cu(OH)2 was mainly responsible for the depression.•► Copper ions can promote the desorption of BX in the presence of Na2CS3.•► Copper ions can promote the formation of Cu(OH)2 in the presence of Na2CS3.