Value adding physico-chemical modifications of shrimp chitosan | |
| Author | Trang Si Trung |
| Call Number | AIT Diss. no.BP-03-4 |
| Subject(s) | Chitosan Value added Shrimps |
| Note | A dissertation submitted in partial fulfillment of the requirements of the degree of Doctor of Technical Science |
| Publisher | Asian Institute of Technology |
| Abstract | In this study, an investigation has been carried out on the value adding modifications of shrimp chitosan by physico-chemical methods. Systematic data have been acquired about the effect of modifications on the quality of shrimp chitosan by varying the degree of deacetylation and the degree of crystallization. New methods has been introduced to decrystallize chitosan and to enhance the resistance of chitosan to lower pl-I. The results of this study have been applied in the use of decrystallized chitosan in the decolorization of textile wastewater. Three chitosan samples, prepared from shrimp shell waste with different degree of deacetylation (75, 87, 96 %) but with a controlled molecular weight of 0.81 million Daltons were used for the determination of the effect of degree of deacetylation on properties of chitosan and its membranes. The result shows that for chitosan in powder form, the dye binding capacity, the fat binding capacity and the crystallinity increased with increasing degree of deacetylation. The water binding capacity, bulk density, and biodegradation decreased with the increasing degree of deacetylation. For membranes prepared from these types of chitosan, it was observed that chitosan membranes increase in tensile strength and crystallinity with higher degree of deacetylation but that swelling index, permeation ability and iodegradation were lower. Chitosan has been regenerated from various acid solutions by dissolution followed by precipitation. The regeneration process appears to be an easy and effective way to purify chitosan and to obtain chitosan with modified physical properties. Chitosan, dissolved in formic acid, acetic acid, propionic acid, lactic acid, citric acid, ascorbic acid or hydrochloric acid, was regenerated by precipitation using 4% NaOH. The regenerated chitosan preparations showed higher purity in terms of decrease in ash content and turbidity in solution. The degree of deacetylation remained the same. The molecular weight of all regenerated chitosan preparations was not significantly decreased compared to that of the original chitosan except for chitosan regenerated from ascorbic acid. Reduction in crystallinity of regenerated chitosan preparations was observed; especially chitosan regenerated from citric acid showed an amorphous Structure. Functional properties of regenerated chitosan such as binding capacity for dye varied with acid treatments. It is concluded that regeneration of chitosan from organic acid solvents has a strong potential for purification of chitosan and physico-chemical modification of chitosan. Two methods to decrystallize chitosan have been investigated in detail using citric acid and sulfuric acid, receptively. The resultant chitosan powder has a strongly reduced crystallinity and a much higher binding capacity for small molecules like pigments used in textile industry. A method is described to prepare chitosan from shrimp shells with a low degree of crystallinity (10%) and a high anionic dye binding capacity. Decrystallized chitosan has been applied for the purification of textile industry dye effluent. Decolorization of textile dye effluent by decrystallized chitosan reached 90% completion within l0 min, and can be carried out over a pl-I range from 4.5 to 8.1. Decrystallized chitosan can be regenerated by 2 M HZSO4 and can be reused more than 10 times. Reinforcement of chitosan in powder and membrane form in order to make it stable at acidic condition was earned out by sulfuric acid treatment. The stability and crystallinity of the treated chitosan were investigated. The treated chitosan samples Were highly stable even at very low pH. During 24 h of immersion in acidic solution ofpl-I l, only 7 % of the chitosan membrane material dissolved while total dissolution (100 °/0) was observed for normal chitosan. The treated chitosan and its membrane have low crystallinity. Moreover, the treated membrane has higher tensile strength compared to that of untreated membrane. This treated chitosan might be applied in enzyme immobilization, in metals and dye adsorption, and as drug release control carrier facing low pH conditions. The overall conclusion is that chitosan, a biodegradable and biocompatible natural polymer with many practical applications in various fields, that can be physically modified by some simple treatments to obtain new chitosan preparations with different physico- chemical properties. Especially, decrystallized chitosan has shown to be a promissing absorbent for dccolorization of wastewater from textile industry. This chitosan has been proposed for application in enzyme and cell immobilization, fat and cholesterol binding and wastewater treatment. |
| Year | 2003 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Bioprocess Technology (BP) |
| Chairperson(s) | Stevens, Willem F. ; |
| Examination Committee(s) | Suwalee Chandrkrachang;Amararatne Yakupitiyage;Nguyen Thi Kim Oanh;Udomchai Chinadit;Chen, Rong H.; |
| Scholarship Donor(s) | Asian Institute of Technology ; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2003 |