Novel of TiO2/Ag3PO4/Bentonite Composite Photocatalyst: Preparation, Characterization, and Application for Degradation of Methylene Blue in Aqueous Solution

Novel of TiO2/Ag3PO4/Bentonite Composite Photocatalyst:

Preparation, Characterization, and Application for Degradation

of Methylene Blue in Aqueous Solution

Thi Thanh Thuy Tran,1 Van Dat Doan,1 Tran Thai Thuan Ho,1

Van Thuan Le,2 and Hoai Thuong Nguyen3,4,*

1

Faculty of Chemical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh City, Vietnam. 2

Center for Advanced Chemistry, Institute of Research and Development, Duy Tan University, Danang, Vietnam. 3

Division of Computational Physics, Institute for Computational Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam. 4

Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam.

Received: April 24, 2018 Accepted in revised form: July 7, 2018

The present work is devoted to the synthesis of a novel photocatalyst of TiO2/Ag3PO4/bentonite composite and

its utilization for degradation of methylene blue (MB) in aqueous solution under visible light irradiation. The

synthesized catalyst was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field

emission scanning electron microscopy, Brunauer-Emmett-Teller method and energy-dispersive X-ray tech￾niques. Degradation conditions were optimized as pH of 7, catalyst loading of 0.1 g, initial MB concentration of

50 mg/L at room temperature with composition weight ratio of TiO2:Ag3PO4:bentonite corresponding to

1:0.15:1, respectively. Results indicated that photocatalytic activity of this material was significantly improved

due to the combination of advantages of its components. Kinetics of degradation process fitted well with a

pseudo first-order model. A possible degradation mechanism was proposed and analyzed in detail. In addition,

recycling study demonstrated a high stability of the catalyst over five continuous cycles of MB degradation.

Keywords: degradation; methylene blue; photocatalysis; TiO2/Ag3PO4/bentonite; visible light

Introduction

Development of various kinds of industries in the past

decades has led to the alarmingly severe environmental

pollution, especially water pollution, caused by a large

amount of wastewater (about 2 million tons) discharging into

eco-systems every day; therein a major contributor to that is

related to persistent organic pollutants from dyeing and tex￾tile industries (Hessel et al., 2007; Earnhart, 2013). In this

context, various detoxification methods, including biological

methods using bacterial, coagulation–flocculation, precipi￾tation, reverse osmosis, oxidation with strong oxidizing

agents, or advanced oxidation with many kinds of photo￾catalysts, have been employed (Holkar et al., 2016; Hou

et al., 2017; Orge et al., 2017; Paz et al., 2017). Among these

methods, photocatalysis using inexhaustible solar energy

source has received enormous interest because of its potential

application in solving environment and energy problems

(Zayani et al., 2009; Olya et al., 2013; Battiston et al., 2014).

Since the concept of photocatalysis has come into being, in

chemistry it refers to the reactions that occur under the si￾multaneous interaction of light and a catalyst; therein light is a

trigger factor to initiate the reaction. After being excited by

light, the catalyst creates electron–hole pairs for electron

exchange between its surface and adsorbed substances

through semiconductor bridges. It then accelerates photo￾chemical process through a series of oxidation-reducing re￾actions (Dionysios et al., 2016).

TiO2 is one of the most promising photocatalysts that has

attracted great attention from scientific community because

of its chemical inertness, eco-friendly nature, and high pho￾tocatalytic activity by means of a high degradation efficiency

of organic pollutants under light exposure (Mishra et al.,

2017). TiO2 with a band-gap of around 3.2 eV has good

properties in charge transport and photo-electronic genera￾tion, supporting the formation process of reactive oxygen

species in an aqueous medium such as hydroxyl radicals OH

and superoxide anions O

2 that are capable of degrading

organic pollutants (Kim et al., 2016). In general, however,

3.2 eV in the term of photo-electronic generation is a quite

large band-gap that only ultraviolet (UV) light at wavelength

k < 380 nm can stimulate electrons from the valence band

(VB) onto the conduction band (CB) to cause photocatalysis.

This limits the photocatalytic potential of TiO2, thereby

narrowing the applicability of this material (Kim et al., 2015;

Islam et al., 2016; Miao et al., 2016; Zoltan et al., 2016).

To use visible light in the photocatalytic process of TiO2,

many metals such as Ag, Ni, Au, and Pt (Vasilaki et al., 2015),

*Corresponding author: Division of Computational Physics, In￾stitute for Computational Science, Ton Duc Thang University, Ho

Chi Minh City, Vietnam; and Faculty of Electrical and Electronics

Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet￾nam. Phone: +84-8688-44-310; Fax: +84-28-37-755-055; E-mail:

[email protected]

ENVIRONMENTAL ENGINEERING SCIENCE

Volume 00, Number 00, 2018

ª Mary Ann Liebert, Inc.

DOI: 10.1089/ees.2018.0179

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