A sample of N, N, N-trimethylchitosan chloride (TMC) was prepared and its ability to remove arsenate and chromate from an aqueous solution was evaluated. The removal capacity was quantified by a liquid-phase polymer-based retention system. A washing method was used to determine the effect of pH, molar ratio, contact time, and interfering ions on the removal of the anions. The results showed that TMC exhibits a high affinity for the divalent species HAsO42- and CrO42- because the majority of the retention capacity occurred at pH values between 6 and 10. A removal maximum was found for experiments with a 10:1 molar ratio and pH 8.0, achieving a 73.0 % removal of As(V) and a 94.0 % removal of Cr(VI). The evaluation of the effect of the contact time of the polymer-SR (species to remove) solution prior to diafiltration revealed that the interaction between TMC and the anions is produced rapidly. Furthermore, TMC selectivity in the presence of interfering ions, such as chloride and sulphate, and maximum retention capacity were evaluated. Finally, permeate flux behaviour was briefly discussed under different conditions of removal.