Since compactness is a disadvantageous characteristic of chitosan-based membranes, two different methods were used to increase the porosity of the chitosan/poly(vinyl alcohol)/polyethyleneimine (CS/PVA/PEI) membrane, and its effect on copper ion adsorption was studied. In the first method, selective dissolution of poly(vinyl pyrrolidone) (PVP) induced porosity and for the second method, a mixed solvent system, which consists of a volatile solvent (acetone), was used to improve the porosity of the membrane. Different percentages of PVP showed inadequate performance, but acetone improved the operation efficiency of adsorption. The membranes were characterized by the analysis of FT-IR, SEM, BET, swelling degree, and porosity. Adding acetone to the membrane mixture solution increased the adsorption capacity by about 50%. The experimental results at different temperatures (25, 35, 45 and 55 °C) showed that the Cu2+ uptake was decreased with an increase in the temperature. Furthermore, pH had an important effect on the adsorption capacity of the copper ions. Nonlinear regression was applied to fit the isothermal and kinetic models. Reusability test with 0.05 M Na2EDTA showed less than 8% reduction in adsorption capacity of the modified membrane after four cycles of adsorption–regeneration.

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