Graphene oxide supported Fe₃O₄-MnO₂ nanocomposites for adsorption and photocatalytic degradation of dyestuff: ultrasound effect, surfactants role and real sample analysis

ABSTRACT

Present work demonstrates the synthesis, characterisation and application of a novel hybrid nanocomposite GO@Fe₃O₄-MnO₂ for adsorption and catalytic degradation of dyestuff malachite green and tartrazine from wastewater. The nanocomposite GO@Fe₃O₄-MnO₂ was characterised by FT-IR, XRD, SEM-EDS and pH_zpc. Effects of various optimising parameters such as contact time, solution pH, surfactants, light, adsorbent dose, ultrasonication and coexisting ions were investigated. The removal efficiencies of malachite green and tartrazine were observed as high as 99.9% and 98% under direct sunlight, respectively. The adsorption kinetics follows the pseudo-second order model (R² = 0.99) where k₂ for malachite green and tartrazine were 0.0097 and 0.0011 g mg⁻¹ min⁻¹, respectively, that means adsorption was controlled by chemisorption. Equilibrium adsorption isotherm of these dyes was analysed in the context of Langmuir and Freundlich models, and the maximum adsorption capacity for Langmuir isotherm was found to be 8.0 and 5.1 mg g⁻¹ for malachite green and tartrazine, respectively. The percentage removal was initially low, but when the ultrasound was irradiated, the removal percentage (96% for malachite green and 98% for tartrazine) was drastically increased because of the formation of highly active ^•H and ^•OH radicals in the water through the decomposition of water molecules by the formation of hot spots. On treatment with H₂O₂, advance oxidation processes were observed with high remediation percentage (99.5% for malachite green and 98% for tartrazine) of dye. The synthesised GO@Fe₃O₄-MnO₂ was finally used for the treatment of dyes from real water samples. The used nanocomposite was separated using an external magnet and recycled with 0.1 N HCl or 0.1 N NaOH as desired.

KEYWORDS:

• Graphene nanocomposite
• hazardous dye
• magnetic photocatalyst
• ultrasonication
• wastewater treatment

Acknowledgments

Dr. Gautam is thankful to UGC for DSK–PDF (No. F. 4-2/2006(BSR)/17-18/0271). Mr. Ankit, Ms. Shreanshi and Ms. Jyoti are grateful to UGC for providing research fellowships Chem./2018-19/RET/Sept.18-term/1/4809, Chem./2019-2020/RET-2/Sept.19-term/1/975 and Chem./2021/RET-Ex/March-21-term/37/240, respectively. We are thankful to Mr. Subham Das for help during experimental work. We are grateful to BHU Varanasi for providing characterisation facility.

Authors contributions

AKS: Designed and performed experiment, data interpretation and wrote first draft; RKG: performed experiment, conceptualisation and illustration draw; SA: review and editing: JP: synthesis and characterisation; IT: arranged instrumentation facilities, supervision and finalised manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03067319.2022.2091930