Elsevier

Materials Letters

Volume 168, 1 April 2016, Pages 143-145
Materials Letters

Novel Bi2O3 loaded sepiolite photocatalyst: Preparation and characterization

https://doi.org/10.1016/j.matlet.2016.01.051Get rights and content

Highlights

  • Bi2O3 loaded sepiolite was synthesized to make Bi2O3 powder dispersed effectively.

  • The absorption edge of 25% Bi2O3/sepiolite was about 555 nm.

  • The specific surface area of 25% Bi2O3/sepiolite was 7.640 m2/g.

  • Bi2O3/sepiolite showed good photocatalytic activity for malachite green degradation.

Abstract

Novel Bi2O3 loaded sepiolite photocatalysts were first prepared to overcome the problem that the Bi2O3 powder particles are easily agglomerated. The crystalline phases, morphologies, specific surface areas and light absorption abilities were characterized by XRD, SEM, BET and UV–vis diffuse methods, respectively. And malachite green (MG) was used as the model pollutant to investigate their photocatalytic activities. Bi2O3 particles were scattered on the surface of the sepiolite from the XRD analysis and the SEM observation. The 25% Bi2O3/sepiolite had the largest specific surface area and the smallest band gap energy, which contributed to its strongest adsorption ability and efficient photocatalytic degradation ability for MG.

Introduction

Organic substances, such as organic dyes, have caused considerably damage to the environment and human beings because of their high toxicity character. Bi2O3, a semiconductor with band gap of 2.8 eV, has been widely used to decompose organic dyes, such as Rhodamine B [1], [2], [3], [4], methyl orange [1], [3], methyl blue [3], malachite green [5] and demonstrated to be an effective visible light-driven photocatalyst.

However, ultra fine Bi2O3 powders easily agglomerate into larger particles, resulting in weakening of photocatalytic performance. Dispersing Bi2O3 particles onto clay minerals is a promising method to resolve the agglomeration problem of Bi2O3 powders.

Sepiolite is a fibrous, hydrated Mg–Al silicate clay mineral. Its each structural block consists of two tetrahedral silica sheets and a central octahedral sheet containing magnesium, resulting in zeolite-like channels. The unique pore structure with interior channels contributes for its strong adsorption ability [6]. Recently, sepiolite has been employed as the support to prepare TiO2 loaded sepiolite photocatalyst and the results showed that loading TiO2 onto sepiolite indeed improved the dispersion situation of TiO2 particles and ultilized the adsorption ability of sepiolite sufficiently [6], [7], [8], [9], [10].

To our best knowledge, there is no report about loading Bi2O3 on sepiolite. In order to overcome the disadvantage that Bi2O3 powder particles are easily agglomerated and improve the photocatalytic activity of Bi2O3 powder, Bi2O3/sepiolite photocatalysts were explored to be fabricated and their performances relating to photocatalytic activity were characterized.

Section snippets

Materials

Raw sepiolite was purchased from Shijiazhuang Xinlei Mining. All reagents such as Bi(NO3)3·5H2O, HNO3, NaOH were of analytical grade and were used without further purification.

Preparation of photocatalyst

Refinery of sepiolite: the raw sepiolite powder was added into deionized water (the ratio of sepiolite mass and deionized water volume was 1:20) and stirred for 120 min, then the suspension was centrifuged and the solid was dried at 120 °C.

The Bi2O3/sepiolite photocatalysts with 5%, 25% and 50% mass percent of Bi2O3 were

XRD

Fig. 1 shows the XRD patterns of the samples. It can be seen that all the samples were well crystallized. 5% Bi2O3/sepiolite almost had the same pattern as sepiolite for the very low content of Bi2O3. When the content of Bi2O3 reached 25% and 50%, some characteristic diffraction peaks labeled by circle were observed, which could be indexed as Bi2O3 (JCPDS file no. 27-0050), indicating that Bi2O3 particles were loaded onto the sepiolite.

SEM and specific surface area

The morphologies of sepiolite and 25% Bi2O3/sepiolite are

Conclusion

Bi2O3 loaded sepiolite photocatalysts were synthesized successfully. The Bi2O3 particles were well dispersed on the surface of the sepiolite, which resolved the agglomeration problem of Bi2O3 powders. The absorption edge of 25% Bi2O3/sepiolite reached 555 nm. Besides, its specific surface area was increased to 7.640 m2/g, which was confirmed by the very low concentration of MG after being placed in the dark. After irradiation for 180 min, approximately 98.15% of MG was degraded by 25% Bi2O3

Acknowledgments

This work is financially supported by the Youth Innovation Foundation of Tianjin University of Science & Technology (No. 2015LG11).

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