Efficient removal of methylene blue dye by a hybrid adsorption–photocatalysis process using reduced graphene oxide/titanate nanotube composites for water reuse

Accepted Manuscript

Title: Efficient removal of methylene blue dye by a hybrid

adsorption–photocatalysis process using reduced graphene

oxide/titanate nanotube composites for water reuse

Authors: Chi Hieu Nguyen, Ruey-Shin Juang

PII: S1226-086X(18)30946-8

DOI: https://doi.org/10.1016/j.jiec.2019.03.054

Reference: JIEC 4474

To appear in:

Received date: 8 October 2018

Revised date: 24 December 2018

Accepted date: 28 March 2019

Please cite this article as: Nguyen CH, Juang R-Shin, Efficient removal of methylene

blue dye by a hybrid adsorption–photocatalysis process using reduced graphene

oxide/titanate nanotube composites for water reuse, Journal of Industrial and

Engineering Chemistry (2019), https://doi.org/10.1016/j.jiec.2019.03.054

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1

Revisions submitted to Journal of Industrial and Engineering Chemistry

(Research Article)

(JIEC_2018_392_R1)

Efficient removal of methylene blue dye by a hybrid adsorption–photocatalysis

process using reduced graphene oxide/titanate nanotube composites for water reuse

Chi Hieu Nguyen1,2, Ruey-Shin Juang1,3,4*

1Department of Chemical and Materials Engineering, Chang Gung University, Guishan, Taoyuan 33302, Taiwan

2

Institute of Environmental Science, Engineering and Management, Industrial University of Ho Chi Minh City,

Ho Chi Minh City, Vietnam

3Division of Nephrology, Department of Internal Medicine, Chang Gung Memorial Hospital, Linkou, Taiwan

4Department of Safety, Health and Environmental Engineering, Ming Chi University of Technology, Taishan,

New Taipei City 24301, Taiwan

*Corresponding author: Professor Ruey-Shin Juang

E-mail: [email protected]

Address: Department of Chemical and Materials Engineering, Chang Gung University, 259 Wenhua First Road,

Guishan, Taoyuan 33302, Taiwan

Graphical Abstract

This scheme proposes possible photocatalytic mechanism over rGO/TNT composites. TiO2 nanotubes are

dispersed well on the surface of rGO sheets. Tubular structure of TiO2 improves adsorption ability for dye. Under

photon irradiation, electrons (e

-

) are excited from the valence band (VB) to conduction band (CB), leading to the

formation of holes (h

+

) in the VB. The holes with strong oxidation ability scavenge water molecules on the surface

of TNTs and generate highly reactive hydroxyl radical (·OH). Also, they attack and convert dye molecules to by￾products. The photoinduced electrons (e

-

) reduce the absorbed oxygen molecule to produce superoxide radicals

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2

(·O2

-

), which may directly oxidize organic pollutant into small molecules; and, part of ·O2

-

can react with H+

and

generate H2O2, which is further excited by electrons and changed into ·OH radicals. These active radicals attack

dye molecules and degrade them into the intermediates and final products such as CO2 and H2O. Normally, the

electron-hole pairs for TNTs are ready to be recombined, resulting in poor photoactivity. Herein, the photoinduced

electrons can be trapped by rGO, leading to electron-hole separation. Therefore, the adsorption and photocatalytic

ability of rGO/TNT composites is enhanced.

Highlights

 Reduced graphene oxide/titanate nanotube (rGO/TNT) composites are hydrothermally prepared as

novel photocatalysts.

 Unlike methyl orange (MO), rGO/TNT composite achieves higher decolorization/mineralization of

methylene blue (MB) than P25-TiO2.

 Unlike MO, removal of MB using rGO/TNT composites is due to the synergy of adsorption and

photocatalysis.

 GO content in rGO/TNT composite has a great effect on adsorption and photocatalytic activity for

cationic dye.

 Incorporating rGO in rGO/TNT composite will extend its photocatalytic ability to the visible light

region.

Abstract

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