Functionalization Of Cellulose Nanofibers With Phthalocyanine For Decoloration Of Dye Wastewater

Cellulose nanofibers are promising supports for functional molecules immobilization due to several attractive characteristics:low cost, nontoxicity, high physicochemical stability, and high density of hydroxyl groups from cellulose; and very large surface-to-volume ratio, good mechanical properties as well as easily tunable surface from nanofiber. In this thesis, cellulose nanofibers were selected as support of cobalt tetraaminophthalocyanine (CoPc) catalyst. CoPc was covalently immobilized onto the surface of cellulose nanofibers and the prepared heterogeneous catalyst was used for decolorizing simulated dye wastewater. The main experiments and results are summarized as follow.Cellulose acetate was electrospun into nanofiber mats (CA-NM), CoPc was covalent immobilized onto the surface after hydrolyzation and oxidation. The CoPc functionalized nanofiber mats (CoPc-NM) was used for the treatment of a simulated dye wastewater:reactive red X-3B solution. In acidic solution, CoPc-NM has high adsorption capacity to anionic dye molecules, which can further promote the catalytic oxidation efficiency when H2O2was present as oxidant. At pH2, more than90%of reactive red X-3B can be eliminated by CoPc-NM/H2O2in90min.To further minimize the effects of diffusion limitation and steric hindrance and improve the decoloration efficiency of the heterogeneous catalyst, a novel CoPc functionalized, spacer arm attached cellulose nanofiber mats (CoPc-spacer-NM) nanomaterial was prepared and used for decoloration of the simulated dye wastewater. Compared with CoPc-NM, CoPc-spacer-NM shows much higher adsorption capacity when conducted under acidic condition, which enhances the catalytic oxidation rate of dye molecules when H2O2was used as oxidant. Dye wastewater can also be efficiently decolorized by CoPc-spacer-NM/H2O2system under basic condition. Despite a relatively weak adsorption capacity, the catalytic oxidation rate was73.85μimol·min-1·g-1at pH10. Electron paramagnetic resonance (EPR) results suggest that the catalytic oxidation process involves the formation and reaction of hydroxyl radicals. Gas chromatography-mass spectra (GC-MS) show that reactive red X-3B is mainly decomposed to biodegradable aliphatic acids, such as maleic acid, fumaric acid, glutaric acid and adipic acid. A catalytic membrane reactor was assembled based on CoPc-spacer-NM. At optimal operational condition,90%of dye molecules can be eliminated within9min.To enhance the electron transfer efficiency of CoPc during the catalytic oxidation process, a multiwalled carbon nanotube doped, CoPc functionalized, spacer arm attached cellulose nanofiber mats (MWNT/CoPc-spacer-NM) was prepared. Due to its well conductivity, the introduction of MWNT can accelerate the electron transfer of MWNT/CoPc-spacer-NM/H2O2, the catalytic oxidation efficiency is20%higher when compared with CoPc-spacer-NM/H2O2system.