Graphene quantum dot and iron co-doped TiO2 photocatalysts: Synthesis, performance evaluation and phytotoxicity studies

Muhammad Saqib Khan; Nadia Riaz; Ahson Jabbar Shaikh; Jehanzeb Ali Shah; Jamshaid Hussain; Muhammad Irshad; M Saifullah Awan; Asad Syed; Jean Kallerhoff; Muhammad Arshad; Muhammad Bilal

doi:10.1016/j.ecoenv.2021.112855

Graphene quantum dot and iron co-doped TiO₂ photocatalysts: Synthesis, performance evaluation and phytotoxicity studies

Ecotoxicol Environ Saf. 2021 Dec 15:226:112855. doi: 10.1016/j.ecoenv.2021.112855. Epub 2021 Oct 7.

Authors

Affiliations

¹ Department of Environmental Sciences, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
² Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
³ Department of Biotechnology, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan.
⁴ Nano Science and Technology Department, National Centre for Physics (NCP), Shahdra Valley Road, Islamabad 44000, Pakistan.
⁵ Department of Botany and Microbiology, College of Science, King Saud University, P.O. 2455 Riyadh 11451, Saudi Arabia.
⁶ Ecolab, Université de Toulouse, Toulouse, France.
⁷ Institute of Environmental Sciences and Engineering, School of Civil and Environmental Engineering, National University of Sciences and Technology, Islamabad 44000, Pakistan. Electronic address: marshad@iese.nust.edu.pk.
⁸ Department of Environmental Sciences, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan. Electronic address: mbilal@cuiatd.edu.pk.

PMID: 34628153
DOI: 10.1016/j.ecoenv.2021.112855

Abstract

The present study reports the synthesis, photocatalytic decolorization of reactive black 5 dye and phytotoxicity of graphene quantum dots (GQDs) and iron co-doped TiO₂ photocatalysts via modified sol gel method. GQDs were synthesized by direct pyrolysis of citric acid (CA). Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS), Raman spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) and photoluminescence spectroscopy (PL) were used to determine the physicochemical properties of the best performing photocatalysts. The results indicated improved physicochemical properties of GQD-0.1Fe-TiO₂-300 with root mean square roughness (Rz) (33.82 nm), higher surface area (170.79 m² g^-1), pore volume (0.08 cm³ g^-1), and bandgap (2.94 eV). Moreover, GQD-0.1Fe co-doping of TiO₂ greatly improved the photocatalytic decolorization efficiency for RB5 dye. The photocatalytic reaction followed the pseudo first order reaction with gradual decrease in K_app values for increment in RB5 concentration. The K_C value was obtained as 2.45 mg L^-1 min^-1 while the K_LH value was 0.45 L mg^-1 indicating the heterogeneous reaction system followed the Langmuir-Hinshelwood isotherm and simultaneously occurring adsorption and photocatalytic processes. Photocatalytic reaction mechanism studies exhibited the holes and OH radicals as the main active species in the GQD-0.1Fe-TiO₂-300 responsible for the decolorization of RB5. The proposed reaction pathway showed that both Fe-TiO₂ and GQDs play important role in generation of electrons and holes. Additionally, GQD-0.1Fe-TiO₂-300 were durable up to four cycles. Phytotoxicity assay displayed that treated water and best performing photocatalysts had no effect on Lycopersicon esculentum seed germination. Therefore, the proposed system can pave a viable solution for safe usage of dye loaded wastewater and effluent for irrigation after treatment.

Keywords: Graphene quantum dots; Photocatalysis; Phytotoxicity; Reaction kinetics.

MeSH terms

Catalysis
Graphite* / toxicity
Iron
Quantum Dots* / toxicity
Titanium / toxicity

Substances

titanium dioxide
Graphite
Titanium
Iron