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Immobilization of Laccase onto Graphene Oxide-based Nano-Composites for Decolorization of Colored Wastewaters

kashefi, Saeed | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51831 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Borghei, Mehdi; Mahmoodi, Neyazmohammad
  7. Abstract:
  8. Using free laccase, enzymatic decolorization of two azo dyes were optimized. The optimum conditions with the aim of maximizing the decolorization of AB92 dye (92.30%) were: dye concentration = 11.85 mg L-1, pH = 5.1, and enzyme concentration = 98.37 mg L-1. While, these conditions to achieve the maximum decolorization yield of DR23 (95.60%) were: dye concentration = 17.68 mg L-1, pH 3.7 and enzyme concentration =97.89 mg L-1.In the second part, the laccase enzyme was covalently immobilized onto GO nanosheets. At the concentration of graphene oxide and laccase enzyme equal to 1 mg mL-1 and 0.9 mg mL-1, respectively, the enzyme loading was 156.5 mg g-1 and the immobilization efficiency was 64.6%. The optimum concentration of the nanobiocatalyst was 300 mg mL-1 for both of dyes. In this conditions, the biodegradation of AB92 and DR23 dyes were 48.7% and 88.7%, respectively.In the third section, GO synthesis, its step-by-step modification with CuFe2O4 nanoparticles, and then their chemical modifcation, was presented. The optimum ratio of the enzyme to support was 0.9 (the concentration of the magnetic substrate was 1mg mL-1), in which the maximum enzymatic loading was 209.7 mg g-1 and the maximum immobilization efficiency was equal to 77.5%. The Lac-fMGO biocatalyst can maintain over 80% of its initial activity after 10 consecutive cycles of reaction and isolation.In the final part of the study, two different commercial laccase enzymes were immobilized onto various agarose derivatives. The best result was obtained for EDA-SIGMA-Aga-GLY biocatalyst, which despite their low mean recovery rate (25%), had a half-life of about 9 hours and was 6.1 times more stable than free enzyme
  9. Keywords:
  10. Enzyme Stabilization ; Laccas Enzyme ; Graphene Oxide ; Magnetic Nanocomposite ; Biocatalyst ; Waste Treatment ; Dye Removal

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