Preparation and characterization of nano structured Ba2SnO4 as a novel photocatalyst material for the chromate reduction

S Omeiri,N Allalou,Y Bessekhouad,G Rekhila,M Trari

doi:10.1007/s13204-013-0276-z

S Omeiri, N Allalou + Show 3 more

Open Access

https://doi.org/10.1007/s13204-013-0276-z

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Abstract

The photo-electrochemical properties of the layered perovskite Ba2SnO4, prepared by nitrate route are reported for the first time. The oxide exhibits a direct optical transition at 2.98 eV, attributed to the charge transfer O2−: 2p → Sn4+: 5s and possesses a chemical stability over the whole pH range. The Mott Schottky plot in acidic medium is characteristic of n type conductivity with a flat band potential Efb of −0.84 VSCE and an electron density ND of 1.14 × 1017 cm−3. The electrochemical impedance spectroscopy reveals the bulk and grain boundaries contributions. Ba2SnO4 is of interest for the environmental protection. At pH 2.5, its conduction band (CB, −0.86 VSCE) is below the HCrO4− level, yielding a spontaneous reduction to Cr3+ under UV light. The reduction is optimized with respect to the Cr(VI) concentration. The photo reduction follows a pseudo-first-order kinetic and the data fit well the Langmuir–Hinshelwood (L–H) model with an apparent rate constant of 0.18 h−1 for an initial concentration of 50 ppm. The chromate reduction under solar light is studied under optimized conditions. In presence of oxalic acid, 73 % of initial concentration disappears after ~2 h of irradiation.

Highlights

Environment protection has become a field of high priority because of the large scale aquatic pollution (Karunakaran et al 2009; Gherbi et al 2011)
The applications of the photocatalysis are numerous and it is the environmental aspect that we develop through the reduction of chromate, recognized as a worldwide problem (World Health Organization International Agency for Research on Cancer 1990)
The X-ray diffraction (XRD) pattern (Fig. 1) is characteristic of single phase; all peaks are indexed in the perovskite structure with a quadratic symmetry (SG: I4/mmm, JCPDS) in agreement with the JCPDS card N° 40–0010

Summary

Introduction

Environment protection has become a field of high priority because of the large scale aquatic pollution (Karunakaran et al 2009; Gherbi et al 2011). The Mott Schottky plot in acidic medium is characteristic of n type conductivity with a flat band potential Efb of -0.84 VSCE and an electron density ND of 1.14 9 1017 cm-3. The photo reduction follows a pseudo-first-order kinetic and the data fit well the Langmuir–Hinshelwood (L–H) model with an apparent rate constant of 0.18 h-1 for an initial concentration of 50 ppm.

Results

Conclusion