Alginates as Green Flocculants for Metal Oxide Nanoparticles

Flocculation is used for the removal or separation of colloids, e.g. in water treatment and mineral processing. Alginates are linear, anionic biopolymers composed of mannuronic (M) and guluronic (G) acids. The relative amount and distribution of M and G impact the ion-binding and gel-forming properties of the polymer, but still no one has yet addressed the impact of alginate composition on flocculation of nanoparticles or mineral particles. Our results showed that the distribution of G was important for flocculation, especially when Ca 2+ was used as activating ion. With Ce 3+ as activating ion, the shape and size of flocs were affected by alginate acetylation. This work expands the knowledge about the flocculation behavior of alginates and demonstrates that both bacteria- and algae-derived alginates can be potential biodegradable flocculants of ultrafine particles for mineral processing industry.