Dosing of OH– ions from acrylamide hydrogels for the selective precipitation of copper/cobalt ions in aqueous solutions

•Precipitation of cobalt/copper ions from aqueous solutions using acrylamide hydrogels loaded with OH– ions.•The selectivity in the precipitation disappears when the proportion of OH– ions/metal ions increases.•Procedure that avoids energy expenditure in the separation. The recovery of heavy metals in contaminated water has focused on the adsorption of metal ions by different materials, ranging from artificial and natural zeolites, activated carbon, and some hydrogels. Although successful in removing metal ions, these methods possess the disadvantage of absorbing all ions within the solution. In the present work, acrylamide hydrogels were used as storers and dispensers of OH– ions to aqueous solutions containing cobalt and copper ions to carry promising the precipitation reaction of the metal hydroxides and to determine the selectivity in the precipitation of copper hydroxide or cobalt hydroxide, depending on the ratio of a hydrogel loaded with OH– ions and the mass of the metal solution, varying the ratio of cobalt/copper in the aqueous solution.