The properties of carboxymethylcellulose (CMC) complexes and Co2+ and Al3+ are reported in this work. The complexing power of CMC was greater to Al3+ than to Co2+, 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 Al3+, Co2+, Cu2+, Mo6+(initially in the form of molybdate) and VO2+ 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 b0.3 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 Al3+ ions in the water rising from the use of alum.

The authors wish to thank Fundação Araucária — Paraná — Brasil, CNPq, Professor Dr. Thomas Heinze, University of Jena — Germany, and The Microscopy Center of UFPR, Paraná — Brasil, Vera Regina Pionteke and Professor Dr. Ney Pereira Mattoso Filho

Peer reviewed