Abstract The properties of carboxymethylcellulose (CMC) complexes and Co 2+ and Al 3+ are reported in this work. The complexing power of CMC was greater to Al 3+ than to Co 2+, although it was not possible to determine some of the equilibrium constants. The infrared (IR) spectroscopy and thermal analysis helped in showing the existence of these complexes in the solid state. The films observed by scanning electron microscopy (SEM) provided a certainty that the chains of the biopolymer were not extensively broken by the use of strong mineral acid employed in some of the experimental steps of this study. Two water solutions — bidistilled and deionized water and an Iraí River, Curitiba, PR (Brazil) sample — were obtained by adding metal salts of Al 3+, Co 2+, Cu 2+, Mo 6+(initially in the form of molybdate) and VO 2+ to which CMC was later added as a remediation agent. At different times, aliquots of those water samples were analyzed for their metal contents and showed ability to sequester different percentages of each of the metal ions, therefore, rendering the water samples within the Brazilian and Spanish standards for potable water (varying from < 0.3 to 5 mg/L depending on toxicity). The CMC complexes could be recovered by mechanical removal at the pH where these complexes are not very soluble. This process can be applied to municipal wasterwater treatment plants as CMC is a more cost-effective and non toxic alternative material than commercial employed alum. The metals can be recycled after the decomplexing process from the recovered solid complexes and with the additional benefit of using CMC that it will leave no trace of Al 3+ ions in the water rising from the use of alum.