PRODUCT SEPARATION AND RECOVERY

Membranes of chitin and chitosan and chromatographic columns can be used to separate and recover products. Both substances can also encapsulate adsorbents or coagulate suspended material.

Membrane separation : Chitosan membranes can help to separate water from organic substances. This would be useful in the manufacture of alcohols, in the enrichment of ethanol in the distillation and fermentation industries, and in dehydrating and refining mixed organic solvents. Chitosan, in the form of a hollow-fiber membrane, efficiently permeates water without allowing other substances to pass through. The process works well at 25 C to 70 C, and thus requires just one-half to one-third the energy required by conventional distillation.

Heavy metal ions coordinated to ehitosan membranes can aid separation and concentration of organic compounds from solution. This method increases the separation coefficient 20 to 30 times higher than that of membranes with no heavy metal ions.

Chitosan membranes can be used for reverse osmosis, which might be important in desalination applications. Membranes can be made by neutralizing a film of a chitosan salt to chitosan and then treating it with an organic acid, which acetylates it.

The filtration applications could use a microporous membrane composed of polyamide attached to chitosan with a cross-linking agent. Chitosan coated on a filter can adsorb products from solution.

Chromatographic columns. Chitin derivatives function well as filler in chromatographic columns. Porous beads for this application are made by dissolving chitosan powder in dilute acetic acid, and adding the solution, drop by drop, into a basic solution. Cross-linking by bifunctional reagents improves the physical properties and durability of the material toward organic acids. The resulting beads have a high surface area and compressive strength and can be steam sterilized.

Enzynes such as lysozyme can be isolated by adsorbing the enzyme on chitin and the eluting with an aqueous acid solution. It is also possible to imobilize onchitosan a substance specific for the product you want to purify. Another application is to adsorb the contaminants that you don't want, for exaple, nucleic acids or endotoxins, from a drug preparation.

Encapsulating absorbents : chitosan hydrogels can encapsulate adsorbents. The hydrogel acts as a molecular sieve to exclude particles that might otherwise foul the adsorbent. this system permits one to recover products from dirty broth without problems of adsorbent fouling.

Coagulation : Chitosan can coagulate substances for recovery, for example, to recover cells from fermentation broth. Another application is the crystallization of sugar from syrup using chitosan as a flocculant. for pharmaceutical purification, chitosan derivatives can be used to precipitate nucleic acids and endotoxins, leaving the active substance in solution. chitosan can also remove active carbon from suspension.