Adsorption of copper and nickel ions on macroporous chitosan membrane: Equilibrium study

► The competitive adsorption of Cu and Ni ions on chitosan membrane was investigated. ► Experiments showed the chitosan membrane has higher affinity for Cu2+ than Ni2+. ► Mono and bi-metal adsorption isotherms fitted with various optimization methods. ► Cu and Ni adsorption mechanism is chelation together with electrostatic adsorption.