A review of the use of pullulan derivatives in wastewater purification

Polymer derivatives based on polysaccharides have received increasing attention in wastewater treatment due to their easy availability and environmental friendly nature. Thus, a lot of modified polysaccharides (chitosan, dextran, cellulose, starch, etc) have been used as flocculants/adsorbants for removal of different contaminants. However, from the literature study it was observed that in spite of pullulan advantages (high solubility and flexibility of the backbone compared with other polysaccharides) there was a gap in the current research regarding its application, as such or in derivatized form, in wastewater purification. Therefore, in this article we review some important up-to-date results collated from investigations regarding the flocculating and adsorption properties of some pullulan derivatives which have been already evaluated in synthetic wastewater containing inorganic (clay) or organic (dyes, complex formulations of pesticides) contaminants. The data analyzed highlight the driving forces which govern the polycation/contaminant interactions and hence the flocculation/adsorption mechanisms, and demonstrate there are some parameters related to the characteristics of contaminants, polymers and environment which greatly influence the separation efficiency; the best results in terms of optimum polycation dose/removal efficiency and adsorption capacity were established. The accumulated knowledge provides solid arguments for future research regarding the application of pullulan derivatives in wastewater purification.