# 【8.2 参考资料 14】The 28th Japan-Korea International Seminar on Ceramics, GO-O-6, 2011 年 11 月, Okayama.

# Effect of $ TiO_{2} $ on the distribution of phosphorus due to phase separation of borosilicate glass

Yuki Ohtsuki $ ^{1} $ , Shinichi Sakida $ ^{2} $ , Yasuhiko Benino $ ^{1,*} $ and Tokuro Nanba $ ^{1} $

$ ^{1} $ Graduate School of Environmental Science, Okayama University, Japan

$ ^{2} $ Environmental Management Center, Okayama University, Japan

*benino@cc.okayama-u.ac.jp

Keywords: borosilicate glass, phase separation, phosphorous, glass structure

### 1. Introduction

In fertilizer manufacturing, phosphorus is indispensable element, because it is a vital nutrient for all living organisms, and in Japan, however, there is no yield of phosphorous resources. Recently exports of phosphorous resources have been reduced in the producing countries such as China and USA, and hence recovery and recycling of phosphorus becomes urgent need in Japan.

$$ \mathrm{SiO}_{2}, $$

$$ Al_{2}O_{3} $$

$$ B_{2}O_{3} $$

$$ \mathrm{SiO_{2}} $$

$$ 60-70\% $$

$$ \mathbf{S i O}_{2}\mathbf{-p h a s e} $$

Then, in the authors group, distribution of phosphorous due to phase separation of borosilicate glass has been studied. In the previous study $ [3] $ , it was revealed that $ Al_{2}O_{3} $ promotes distribution of phosphorous to $ SiO_{2} $ -rich phase. In this study, behavior of phosphorus associated with phase separation and the effect of $ TiO_{2} $ addition have been investigated in the ternary $ Na_{2}O-B_{2}O_{3}-SiO_{2} $ system. And then based on the structural analyses, distribution of phosphorus was discussed.

### 2. Experimental procedure

The glasses with compositions given in Table 1 were prepared by a conventional melt-quenching method. The raw materials of reagent grade $ Na_{3}PO_{4} $ , $ Na_{2}CO_{3} $ , $ B_{2}O_{3} $ , $ SiO_{2} $ and $ TiO_{2} $ were mixed thoroughly, and melted in a Pt crucible at $ 1400^{\circ}C $ for 30 min. The melts were quenched by being pressed with iron plates to form glass plates. Differential thermal analyses (DTA) were carried out to determine glass transition and crystallization temperatures, $ T_{g} $ and $ T_{x} $ .

Table 1. Nominal compositions (mol%), $ T_{g} $ and $ T_{x} $ (°C) of the samples.

No.	Na2O	B2O3	SiO2	P2O5	TiO2	Tg	Tx
1	10	40	50	-	-	469	-
2	10	40	47	3	-	450	-
3	10	40	47	3	3	420	-
4	10	40	44	3	5	412	663

Heat treatments for phase separation were performed at 600 - 660 °C, which was the immiscible temperature of the corresponding glasses. After the heat treatment, the glasses were immersed in nitric acid of 1.0 N for 24 h at 90 °C, and the insoluble residues were recovered with vacuum filtration. After being rinsed in water and dried in an oven, silica-rich glasses were obtained.

X-ray diffraction (XRD) measurement was carried out to confirm the crystallization. Chemical compositions of the specimens, such as the glasses before phase separation, the solutions and insoluble residues after immersed in nitric acid were determined by ICP emission spectroscopy and x-ray fluorescence (XRF) spectrometry. Phase separation was confirmed by SEM observation, where the specimens were etched in 5% HF solution for 30 s. Local structures around Si, B, and P were investigated with $ {}^{29} $ Si, $ {}^{11} $ B, and $ {}^{31} $ P MAS-NMR measurements, respectively. For the $ {}^{29} $ Si and $ {}^{31} $ P