Dialysis technology supporting the preparation of acid-resistant picolylamine-based hydrogel sphere for selectively recycling copper, nickel and cobalt from strongly acidic wastewaters

[Display omitted] •Dialysis is used to purify the raw artificial polymers of this adsorbent.•The adsorbent shows potential for direct treatment of strongly acidic wastewaters.•Uptake capacities for Cu, Ni and Co reach 1.844, 1.312 and 0.712 mmol/g at pH 1.0.•Uptake displays good resistance to interferences from inorganic salts and organics.•The coordination geometries around Ni2+ differ from those around Cu2+ or Co2+. Due to the inhibition from high-concentration proton, acid-resistant adsorbents (especially hydrogels) for directly recycling heavy metal cations (HMCs) from strongly acidic wastewaters (pH