The Effect of Different Morphologies of Polyaniline-TiO2 Composites on the Photodegradation of Reactive Black 5 Dye

Khor, Shu Hui (2023) The Effect of Different Morphologies of Polyaniline-TiO2 Composites on the Photodegradation of Reactive Black 5 Dye. Masters thesis, Tunku Abdul Rahman University of Management and Technology.

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Abstract

The release of toxic organic dyes has contaminated the environment. Photocatalysis is widely used as it is an environmentally friendly method able to eliminate the harmful organic compounds by mineralizing it to carbon dioxide and water with the use of light illumination. In this research study, a binary system of PANI-TiO2 photocatalyst with different morphologies including, nanotubes, nanofibers, nanospheres, star micro/nanostructures and leaf micro/nanostructures and a series of L-PANI-TiO2 with different ratio of TiO2 (5%, 10%, 20%, 30%) had been fabricated via chemical oxidation polymerization and the photodegradation towards RB5 toxic dye were evaluated under visible (VIS) light irradiation. Morphologies of PANI is an important factor that may affect the performance of photodegradation. All photocatalysts were characterized by Fourier transformed infra-red (FTIR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy and X-ray diffractometry (XRD), thermogravimetric analysis (TGA), Resistivity meter, Field electron scanning emission microscope (FESEM) along with energy dispersive x-ray (EDX) and Brunauer-Emmett-Teller (BET) technique. 10wt% of TiO2 with PANI, leaf micro-nanostructure (L-PANI-TiO2) was found to be the best photocatalyst (48.8%) among all the morphologies in terms of photodegradation compared with pristine PANI of the corresponding morphology, whereas the photodegradation for L-PANI with 5wt%, 20wt%, and 30wt% of TiO2 was 44.2%, 41.7%, and 35.5%, respectively. Hence, L-PANI-TiO2 (10wt%) was selected to further study by varying the reaction conditions including, dark adsorption time, light reaction time, initial concentration of dye and amount of catalyst in order to achieve the best photodegradation. The tauc plot obtained had demonstrated that PANI-TiO2 composites had lowered the band gap of TiO2 from 3.28eV to the range of 2.68-2.72eV which proved that PANI-TiO2 composites is able to activate in VIS light region while photoluminescence (PL) analysis showed that the electron hole recombination rate of binary composites had been delayed from the range of 10991-45495a.u. to 27910-58927a.u.. Furthermore, L-PANI, TiO2 and L-PANI-TiO2 (5wt%, 10wt%, 20wt% and 30wt%) had been selected to further photodegraded under the same reaction condition. Results showed that these photocatalyst are following pseudo first-order kinetics plot with correlation coefficients of 0.99 and the rate constant was decreased as following the sequence: L-PANI-TiO2 (10wt%) (0.0223 min-1)> L-PANI-TiO2 (5wt%) (0.0121 min-1) > L- 2 PANI-TiO2 (20wt%) (0.0099 min-1)> L-PANI-TiO2 (30wt%) (0.0093 min-1) > L-PANI (0.0078 min-1)> TiO2 (0.0012 min-1). In conclusion, 250mg/L of L-PANI-TiO2 (10wt%) was left in dark condition for 80mins before irradiation was found to be the optimized catalyst as it successfully photodegraded 98.2% of 10ppm RB5 within 180 mins under VIS light illumination.