Recovery of chitosan from aqueous acidic solutions by salting-out: Part 1. Use of inorganic salts

We describe a novel and easy-to-use approach based on salting-out to efficiently recover chitosan from aqueous acidic solutions. Inorganic salts of the Hofmeister series salted-out chitosans of 30 kiloDaltons (kDa), 240 kDa (35 cP) and a 70 cP form of the biopolymer dissolved in dilute HCl or acetic acid. The efficiency generally followed the ranking order of the Hofmeister's salts (SO42- > H2PO4- congruent to HPO42- > NO3-). Temperature (4 degrees C, room temperature, 50 degrees C) did not markedly affect the process. Ammonium sulfate was the Most efficient salting-out agent of chitosans over a wide range of molecular sizes (2300 Da to > 240,000 Da). The solubility (dilute HCl or acetic acid) of the salted-out chitosans varied from readily soluble to nearly insoluble. The choice of the Hotmeister's salt(s) for salting-out chitosans must take into account, (1) the efficiency of recovery, and (2) the molecular size of the chitosans to be recovered. (c) 2007 Elsevier Ltd. All rights reserved.