An easily sedimentable and effective TiO2 photocatalyst for removal of dyes in waterby Ping Jiang, Dengbo Ren, Daiping He, Wensheng Fu, Jian Wang, Mu Gu

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Dye ve a w atal 3B d l si pha 2 on its crystallinity. The anatase TiO calcined at 800 C afforded the highest photocatalytic activity, which semico h atten ions in ed to b show enhanced photocatalytic activity compared to pure anatase powders due to the electron and hole transfer between the two phases [10]. But it is difficult to understand which factors dominate the net photocatalytic activity based on the above physical properties because the photocatalytic reactions proceed through a complicated sequence of competing multistep processes. This demonstrates the importance of understanding the kinetics and r excellentphotoa slurry s ds (flower mal treatm a mixture of TiCl4, ethanol and water [15], a mixture of T and ethylenediamine [16], or through a mild reaction of met with H2O2 aqueous solution containing certain amounts o acid and hexamethylenetetramine [17,18]. Titania microspheres consisted of radial arrays of nanorods [19], nanowires [20] and {001}-facets exposed polyhedra [21] have also been reported.

Herein, anatase TiO2 crystallites have been prepared by hydrothermal homogeneous precipitation from Ti(SO4)2 aqueous solution with urea. The structural evolution with the calcination temperature of the photocatalyst was investigated by X-ray⇑ Corresponding author. Tel./fax: +86 23 6536 2777.

Separation and Purification Technology 122 (2014) 128–132

Contents lists availab ifi .e lE-mail address: (D. He).on electron–hole separation. It is widely accepted that the anatase phase of titania is a relatively ideal photocatalytic material among its three crystalline phases [9]. In addition, it has been known that anatase powders with small fraction of rutile or brookite phase, considerable attentionasphotocatalyst due to thei catalytic activity and facile catalyst-recovery from

Micrometer-sized assembly of 1D titania nanoro sea-urchin-like) has been achieved by hydrother1383-5866/$ - see front matter  2013 Elsevier B.V. All rights reserved. -like or ents of iB2, HF allic Ti f nitriccatalyst for the degradation of harmful pollutants in water and air because of its high stability, nontoxicity and inexpensiveness [4,5].

However, low photocatalytic activity is one of the major factors keeping it from large-scale applications. The photocatalytic activity of TiO2 system depends on its intrinsic properties, such as crystal phase, particle size, crystallinity and specific surface area [6–8].

Furthermore, the catalytic activity of TiO2 also depends strongly immobilised and the addition of electrolytes that favours the coagulation/flocculation of the catalysts as well [11–14], but both strategies show limitations. In the former case the active surface is highly reduced and in the latter case the addition of other chemicals is necessary, increasing both cost and pollutants released to the environment. In recent years, micron-sized aggregates of one-dimensional (1D) titania nanorods, nanotubes or nanowires, attracted1. Introduction

Heterogeneous photocatalysis by green technology, has attracted muc decades due to its potential applicat purification [1–3]. TiO2 has been prov2 was obviously higher than that of commercial Degussa P25 on the photodegradation of X-3B dye in water under ultraviolet light irradiation, and exhibits much faster sedimentability.  2013 Elsevier B.V. All rights reserved. nductor materials, as a tion in the past several air clean-up and water e a very efficient photodynamics of a photocatalytic reaction to establish rational strategies for the imminent development of photocatalytic systems and for future practical applications. Other important factor that compromises the application of photocatalysis at real scale is the final separation of semiconductor from solution when photocatalysis is complete. It has been widely studied the use of photocatalystsKeywords:

Photocatalysis of sulfate ions that are produced during the precipitation of titanium sulfate. The gradually increased photocatalytic activity of the anatase TiO calcined from 110 to 800 C demonstrated strong dependencyAn easily sedimentable and effective TiO of dyes in water

Ping Jiang a, Dengbo Ren b, Daiping He a,⇑, Wensheng a Laboratory of Functional Materials, College of Chemistry, Chongqing Normal University b Sichuan University of Arts and Science, Dazhou 63500, China a r t i c l e i n f o

Article history:

Received 24 December 2012

Received in revised form 28 October 2013

Accepted 30 October 2013

Available online 11 November 2013 a b s t r a c t

Anatase TiO2 crystallites ha aqueous solution with ure temperature of the photoc was investigated using Xhighly resistant to therma crystallinity of the anatase

Separation and Pur journal homepage: wwwhotocatalyst for removal a, Jian Wang a, Mu Gu a ongqing 401331, China been prepared by hydrothermal homogeneous precipitation from Ti(SO4)2 ithout using any additives. The structural evolution with the calcination yst was studied. The photocatalytic activity of the obtained photocatalysts ye as a model pollutant. The as-prepared anatase TiO2 crystallites were ntering, and the calcinations up to 800 C were shown to enhance the se without any rutile phase, which is attributed to the protection of traces le at ScienceDirect cation Technology sevier .com/locate /seppur morphology and particle sizes of the TiO2 were also observed by comparison, the photocatalytic activity of commercial Degussa

P25 TiO2 and TiO2-p800 was also measured under identical conditions. Typically, each TiO2 sample (150 mg) was suspended in 150 ml reactive brilliant red dye X-3B aqueous solution (100 mg/

L). The suspension was magnetically stirred in the dark for 30 min to ensure adsorption/desorption equilibrium in the reaction system, then irradiated under 250 W high-pressure mercury lamp with a wavelength centered at 365 nm at 303 K in thermostated glass reactor. Degradation process of reactive brilliant red dye X-3B was monitored with a UV–vis 2550 spectrophotometer at 540 nm wavelength. 3. Results and discussion 3.1. Structure and morphology of the TiO2 2 cation Technology 122 (2014) 128–132 129scanning electron microscopy (SEM) taken at an accelerating voltage of 20 kV. X-ray photoelectron spectroscopy (XPS) measures were performed with Thermo ESCALAB 250. UV–vis diffuse reflectance spectra (DRS) were determined by a UV–vis spectrophotometer (Shimadzu UV-2550) equipped with an integrating sphere unit. 2.3. Photocatalytic experimentsdiffraction and Raman spectroscopy. The study showed that the anatase phase can be retained even at 800 C without appearance of rutile by the post-treatment. The anatase TiO2 calcined at 800 C has the characteristic of high crystallinity and superior photoactivity, which was obviously higher than that of commercial