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. Chitosan was extracted and characterized using several analyses. The produced chitosan was reacted by glycine and chloroacetic acid. Chemical structures of biosorbents were confirmed. Adsorption efficiencies of the two biosorbents in neutral and alkaline medium at 25°C were determined using atomic absorption spectroscopic analysis. Adsorption capacity of modified biosorbents toward Cu(II) and Co(II) ions was determined and compared to virgin chitosan. The biosorbents showed lower adsorption efficiency toward copper and cobalt ions compared to virgin biosorbent. Furthermore, adsorption capacity of glycine–chitosan was higher than chloroacetic acid–chitosan biosorbents, which attributed to chelating of amino groups than chloro-substituted polymer. Thermodynamic studies showed the spontaneous behavior of the adsorption process of metal ions under the studied conditions. Entropy changes indicate that the adsorption of the metal ions are endothermic process, and lower values of ΔS° indicate the affinity toward metal ions by the biosorbents at different degrees depending on their chemical structures.