Use of chitosan for the removal of metal ion contaminants and proteins from water

Naturally abundant biosorbants such as chitin and chitosan are recognized as excellent metal ligands, forming stable complexes with many metal ions, and serving as effective protein coagulating agents. Chitin isolated from crab processing discards was deacetylated over different time periods in order to obtain three types of chitosans [Type 1 (20 h), Type 2 (10 h) and Type3 (4 h)]. Chitosans so prepared were evaluated for their capacity to chelate metal ions in samples of water obtained from a zinc mining site (Buchans, Newfoundland). Metal chelation capacity of chitosan for wastewater was determined by inductively coupled plasma-mass spectrometry (ICP-MS) at three different pH (5, 6 and 7). Chitosan served as an effective coagulating agent in removing proteins from wastewater as well as for the removal of metal ions [Hg(II), Fe(II), Ni(II), Pb(II), Cu(II) and Zn(II)] from industrial wastewater, especially at pH 7, as measured by ICP-MS. Mercury was best chelated by all three types of chitosan under all pH conditions tested. In the protein flocculation study, Type 1 chitosan showed the best flocculation ability followed by Type 2 and Type 3 chitosans.