The depression of copper-activated pyrite in flotation by biopolymers with different compositions

•Biopolymers’ adsorption on copper-activated pyrite formed Cu-biopolymer complex.•Formation of Cu-biopolymer complex inhibited xanthate adsorption on pyrite surface.•The structure feature of biopolymer played a significant role in pyrite depression.•Higher molecular weight led to higher adsorption amount and pyrite depression.•Functional groups influenced biopolymers’ ability to inhibit xanthate adsorption.