The group of ionic polysaccharides is rather large and most of them are negatively charged. In our review we will focus on chitosan, which is a biopolycation in acidic conditions. The term chitosan is generally referred to the random block copolymer of glucosamine (GlcN) and N-acetyl glu- cosamine (GlcNAc), linked by β-(1–4)-glycosidic bonds. The fraction of N-acetyl glucosamine determines the degree of acetylation (DA). In most cases, chitosan is obtained by alkaline or enzymatic deacetylation of chitin, poly N-acetyl glucosamine (see Fig. 1). The density of chargeable groups along the polymer backbone is determined by the degree of deacetylation. Chitosan is rather well biodegradable and can easily be- come chemically modified by reactions on its amino and hydroxylic side groups [13–15]. The ease of modification, in addition to its antibacterial, antiinflammatory and mucoadhesive properties are reasons why this bio- polymer has found applications in a wide range of fields. For instance it is interacting well with skin and hair and therefore is employed in different types of cosmetic formulations or for food processing [16]. In the medical field chitosan has shown outstanding performance in the field of wound covering and healing [17]. The polyelectrolyte properties of chitosan itself have for instance been employed for purposes of coagulation/flocculation processes, which is a relatively eco-friendly approach compared to methods employed so far [18–20]. Another environmentally relevant ap- plication of chitosan is the removal of heavy metal ion