Treatment of industrial wastewater containing copper and cobalt ions using modified chitosan

•Chitosan have the maximum adsorption efficiency for Cu and Co.•Glycine modified polymer has high adsorption efficiency, and chloroacetic has the lowest.•The adsorption follows Langmuir isotherm.•Intraparticle diffusion model describes the metal adsorption.•The efficiency of Cu and Co metals increased in alkaline medium.