Elsevier

Radiation Physics and Chemistry

Volume 97, April 2014, Pages 366-369
Radiation Physics and Chemistry

Radiolytic synthesis of prismatical PbSO4 microcrystals

https://doi.org/10.1016/j.radphyschem.2013.07.027Get rights and content

Abstract

The prismatical PbSO4 microcrystals were successfully synthesized by precipitating Pb2+ ions with SO42− ions, which were generated from the reduction of K2S2O8 in the presence of EDTA under N2 atmosphere by γ-irradiation. It was found that EDTA and the controlled release of SO42− play important roles in the formation of the microcrystals.

Introduction

Lead sulfate (PbSO4), commonly known as anglesite, has been widely used as scintillator material, electrode material for storage batteries, white dye, quickly dried-paint and so on (Deng et al., 2009, Shao et al., 2005, Xiang et al., 2005). Thus, much effort has been paid to the preparation of PbSO4. In general, PbSO4 is synthesized by adding SO42− ions directly into the solution containing Pb2+ or complexes of Pb2+. Besides, Pb, PbO and PbO2 can also be used as the lead sources (Xiang et al., 2005), and sodium dodecyl sulfate can be used as the source of SO42− (Salavati-Niasari et al., 2012). Up to now, many PbSO4 particles with different morphologies have been synthesized, for example, rod-like nano- and micro-crystals (Shao et al., 2005, Xiang et al., 2005), highly ordered lamellar mesostructure (Deng et al., 2009), plate-like nanocrystals (Zhou et al., 2002), and nanocubes (Katayama et al., 2004, Salavati-Niasari et al., 2012). However, except for nanocubes, the syntheses of PbSO4 particles with other shapes need the help of the soft templates formed by surfactants and polyelectrolytes, i.e., microemulsion (Xiang et al., 2005, Zhou et al., 2002), micelles (Shao et al., 2005), and layered mesophase (Deng et al., 2009). Therefore, it is worthwhile exploring the template-free preparation of PbSO4 particles.

Ionizing radiation (such as γ-irradiation, electron beam irradiation and so on) has been widely used in preparing metal, core–shell metal or alloy, and metal chalcogenide particles (Belloni, 2006, Chen et al., 2010). However, to the best of our knowledge, there is no report on the radiolytic syntheses of PbSO4 particles. Recently, we obtained BaSO4 microspheres, mainly consisting of quasi-spherical nanoparticles, by precipitating Ba2+ ions with SO42− ions, which were generated via the radiolytic reduction of S2O82− (Chen et al., 2008, Chen and Shen, 2010). Nevertheless, as to PbSO4, its solubility (pKsp=7.60) is much larger than that of BaSO4 (pKsp=9.97) (Dean, 1999). Moreover, the cumulative formation constant for Pb2+ with EDTA (log β=18.3) is considerably larger than that for Ba2+ (log β=7.78) (Dean, 1999). Thus, under the precious condition for the radiolytic syntheses of BaSO4, no PbSO4 particles were obtained. There still remains a challenge. Herein, we report the radiolytic syntheses of prismatical PbSO4 microcrystals without the assistant of template, and the effects of EDTA and the controlled release of SO42− on their morphology.

Section snippets

Experimental

An aqueous solution containing 4.0 mmol/L Pb(NO3)2, 4.0 mmol/L K2S2O8 and 4.0 mmol/L disodium ethylenediaminetetraacetate (EDTA) was prepared. The pH value of the solution was adjusted to 1.0 by 4.0 mol/L HNO3 solution. After bubbling with high-purity N2 under anaerobic conditions for 20 min, the solution was irradiated in the field of a 60Co γ-ray source. The dose rate was 60 Gy/min and the absorbed dose was 6 kGy unless otherwise stated.

After irradiation, white precipitates were obtained and washed

Results and discussion

Fig. 1A presents the SEM images of the obtained sample. It can be seen that the product is composed of rod-like microcrystals, with an average length of ca. 5 μm. From the SEM image at higher magnification (inset, Fig. 1A), most of the end of the microcrystals is triangle, with an average side length of ca. 500 nm. In other words, the microcrystals are prismatical, whose average aspect ratio is ca. 10. The related XPS analysis (curve a, Fig. 2A) shows that the binding energies of Pb 4f, S 2p and

Conclusions

The prismatical PbSO4 microcrystals were successfully synthesized by precipitating Pb2+ ions with SO42− ions, which were generated from the reduction of K2S2O8 in the presence of EDTA under N2 atmosphere by γ-irradiation. It was found that EDTA and the controlled release of SO42− play important roles in the formation of the microcrystals. It is believed that the result reported herein will not only help understanding the effect of irradiation on the formation of inorganic particles, but also

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grants nos. 91226112 and 20871009), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant no. 20110001120121) and the Coordinated Research Projects of International Atomic Energy Agency (Research Contract no. 15107). Sincere thanks are due to Ms. Huizhen Zhang (PKU) for the help with SEM experiments. We also thank Dr. Jinglin Xie (PKU) for the help with XPS experiments and thank Mr.

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