Photocatalytic performance of fgnpzno composite for methylene blue degradation under uv-vis light irradiation
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Date
2020-08-01
Authors
Rabiatul Aliah Mahmud
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Abstract
Wastewater crisis has been worsening and pollution abatement should be taken
seriously to reduce the pollutant content in the water stream. Advanced oxidation
processes (AOPs) is known to be an effective method to overcome this raised issue
and photocatalysis is the best option among all. This is due to the utilization of
renewable energy by using semiconductor and at the same time mineralized the
harmful pollutant into non-toxic CO2 and H2O. A novel F-GNP/ZnO composites were
synthesized via facile one-step solvothermal method, where the oxygen
functionalization of GNP and F-GNP/ZnO composites formation were conducted
simultaneously. The low-density oxygen-functional groups attached on GNP was
shown by Fourier Transform Infrared Spectroscopy (FTIR) and correlated with
Raman spectroscopy. The formation of F-GNP/ZnO heterojunction was shown in the
X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), High-Resolution
Transmission Electron Microscopy (HRTEM), Energy Dispersive X-Ray (EDX),
FTIR and Brunauer-Emmett-Teller (BET), that proves on the intimate contact
between F-GNP and ZnO n.p. Then, Photoluminescence (PL) and UV-vis Diffuse
Reflectance Spectroscopy (UV-vis DRS) has successfully provides the evidence on
reducing recombination of electron-hole pairs and wider light absorption compared to
ZnO n.p, respectively. In this study, adsorption and photocatalytic activity of MB was
studied and obtained 45% F-GNP/ZnO composite as the best GNP content in the
composite with adsorption capability and degradation of MB up to 70% and 87%,
respectively. In all, MB removal has successfully achieved with 97% by using 45%
F-GNP/ZnO composite. Here, the high adsorption capability of the composites was
proven by using Brunauer-Emmett-Teller (BET) surface area, where the surface area
is directly proportional to the GNP content in the composites. FTIR and Raman
analyses have shown a significant result, where the interaction that contributed to the
high adsorption was % − % interaction presence between MB molecule and F-GNP
due to the low oxygen density in GNP structure. In addition, process parameter studies
concluded that the best photocatalytic activity of 45% F-GNP/ZnO composite was
achieved using 0.1 g/L catalyst loading in MB with concentration of 10 mg/L and pH
5. Moreover, pseudo-second order for adsorption and pseudo-first order for
photocatalytic activity for 45% F-GNP/ZnO composite were revealed from kinetic
studies and obtained rate of 0.2250 g/mg.min and 0.034 min-1, respectively. Based on
the scavenger test, hydroxyl radical was found to be the most active species that
responsible for the degradation of MB.