Date of Award

2010

Thesis Type

Masters

Document Type

Dissertation

Divisions

Faculty of Science

Department

Institute of Biological Sciences

Institution

Universiti Malaya

Abstract

Synthetic dyes are used for coloration of various materials like textiles, leather and food. Wastewater from dyeing industries constitutes a threat to the environment as many synthetic dyes are often toxic, mutagenic and carcinogenic. Besides, light absorption is hindered by the dyes run-off creating problems to photosynthetic aquatic plants and algae. Biodegradation of waste dyestuff with enzymes provides a viable alternative compared to the often expensive physical/chemical methods. Laccase from Trametes versicolor was chosen in this study as it exhibits low substrate specificity and high ability to oxidize many pollutants which suggested its potential in wastewater treatment and bioremediation. The enzyme was immobilized using calcium-alginate entrapment method. Calcium-alginate entrapment profile was generated to determine the optimum immobilization condition. The observed loading efficiency was greater than 90%. Triphenylmethane dye i.e. Crystal violet was used in this study and decolorization of crystal violet was followed using spectrophotometer. Variables for efficient dye decolorization viz. initial dye concentration (ppm), agitation speed (rpm) and process time (day) were optimized using response surface methodology (RSM) Box-Behnken design protocol. The optimization of process parameters were monitored in a working volume of one hundred milliliters (100 ml) in shake flasks to study the maximum decolorization of crystal violet using the enzyme. Under optimal condition (60 rpm, 5 ppm and within 2 days) high percentage of crystal violet decolorization (40%) was observed. Experiments were scaled-up to two liters (2 L) stirred tank reactor (STR) to examine the effect of impeller types (60° angled blade and 180° curved blade) towards percentage of decolorization. At high speed (160 rpm), 60° angled blade (axial impeller) was better compared to 180° curved blade for both high (30 ppm) and low (5 ppm) initial dye concentration. Conversely, at low speed (60 rpm), axial impeller is better than curve for low initial dye concentration (5 ppm). However, at high initial dye concentration (30 ppm) there was no significant effect in percentage of dye decolorization for both impellers. By choosing appropriate impellers in STR operation, the percentage of crystal violet decolorization can be improved.

Initial

khm

Additional Information

Dissertation (M.A.) – Academy of Islamic Studies, Universiti Malaya, 2010.

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