Difference between revisions of "Team:SDSZ China"

Seafood is almost a common delicacy to everyone. Boston is famous for lobster; Japan is famous for all kinds of sashimi. Few people have paid attention to the huge amount of shells being tossed away annually, but, in fact, there is a special kind of chemical component forming the crustaceans’ outer bones. This is CHITIN（(C8H13O5N)n), an abundant natural macromolecular substance that is rich in common crustaceans such as insects or crabs. In most crustaceans, chitin is combined with calcium carbonate and produces a much stronger composite. This composite material is much harder and stiffer than pure chitin and is tougher and less brittle than pure calcium carbonate. Chitin is insoluble and lack of bioactivity, therefore not widely used in industry.

Because of chitin’s insolubility and bioactivity, it is usually converted by deacetylation to soluble and bioactive CHITOSAN ((C8H13NO5)n (203.19)n). It is white powder and has relatively more industrious usages: Agriculture: used in seed treatment and biopesticide, helping plants to fight off fungal infections. Winemaking: used as a fining agent, helping to prevent spoilage. Industry: used in a self-healing polyurethane paint coating. Medicine: used in bandages, helping to reduce bleeding and serving as an antibacterial agent; used to help deliver drugs through the skin.

The current technology of chitosan production is the treatment with concentrated alkali. The chitin/chitosan process involves the crushing and drying of crab shell or other suitable species of crustaceans such as shrimp shell waste. The product is processed with acid and alkaline in order to remove protein and calcium. The product is then further dried, ground, and packaged as a finished or semi-finished product. A plant set-up would involve a number of pieces of equipment for grinding or particularization, drying, acid and alkaline treatment, packaging and effluent treatment. Crushed shrimp waste was kept in a polyethylene bags at ambient temperature (28±2oC) for 24 hours for partial autolysis to facilitate chemical extraction of chitosan and to improve the quality of chitosan. The Three steps: Demineralization, Deproteinization, and Deacetylation Demineralization: Demineralization of shrimp shell has been carried out with three different concentration of HCI (4%, 3%, 2%) at ambient temperature (28±2oC) with a solid to the solvent ratio 1:5 (w/v) for 16 hours (Toan, 2009). The residue was washed and soaked in tap water until neutral pH. Deproteinization: Deproteinization of shrimp shell was done with 4% NaOH at ambient temperature (28±2oC) with a solid to the solvent ratio 1:5 (w/v) for 20 hours (Toan, 2009). The residue was washed and soaked in tap water until neutral pH. Then purified chitin was dried until it has become crispy. Chitin flakes were grounded to small particles to facilitate deacetylation. Deacetylation: Removal of acetyl groups from chitin was experimented using four different concentration of NaOH (30%, 40%, 50%, 60%) at 650C temperature with a solid to solvent ratio 1:10 (w/v) for 20 hours. (Toan, 2009).The residue was washed until neutral pH with tap water. The resulting chitosan was then dried at cabinet dryer for 4 hours at 65±50 C and prepared for characterization. However, current chitosan production has exposed many drawbacks: deficiency over time and reactant, huge energy cost during the process, instability of product quality, unsafe condition for employees, and, especially, the destructive pollution of basic wastewater. Acid and alkali wasted water can easily pollute waterbody and farmland.