•PANI/CA membrane was studied for adsorbing Hg(II) and Cr(VI).•The new membrane preparation method is convenient, does not use toxic solvent.•The doping agent-Phytic acid improved the adsorptive capacity.•PANI-PA/CA membrane possesses higher BET surface area and electrical conductivity.•PANI-PA/CA membrane has high adsorptive capacity for Hg(II) and Cr(VI). Conductive composite membrane—phytic acid (PA) doped polyaniline (PANI)/cellulose acetate (CA) (PANI-PA/CA) was prepared in a simple and environmental-friendly method, in which aniline was blended with CA/PA solution and polymerized before the phase conversion. The resultant composite membranes were characterized by SEM, EDX, FTIR-ATR, BET and electrical resistance measurements. When used as adsorbent for Hg(II) and Cr(VI) ions, the prepared composite membrane exhibits excellent adsorption capability. The adsorption of Hg(II) and Cr(VI) follows a pseudo-second-order kinetic model and best fits the Langmuir isotherm model, with the maximum adsorption capacity reaching 280.11 and 94.34mgg−1, respectively. The heavy metal loaded composite membrane can be regenerated and reused after treatment with acid or alkali solution, making it a promising and practical adsorbent for Hg(II) and Cr(VI) removal. Tests with river water were also carried out, indicating good performance and application.