Structural behavior of rice husk silica in pressurized hot-water treatmentprocesses

Citation
K. Mochidzuki et al., Structural behavior of rice husk silica in pressurized hot-water treatmentprocesses, IND ENG RES, 40(24), 2001, pp. 5705-5709
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemical Engineering
Journal title
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
ISSN journal
0888-5885 → ACNP
Volume
40
Issue
24
Year of publication
2001
Pages
5705 - 5709
Database
ISI
SICI code
0888-5885(20011128)40:24<5705:SBORHS>2.0.ZU;2-7
Abstract
This paper deals with X-ray fluorescence (XRF), X-ray diffraction (XRD), an d Si-29 nuclear magnetic resonance (29Si NMR) measurements of rice husk sil ica treated under hydrothermal conditions in autoclave and steam-explosion processes. An understanding of the structural behavior of rice husk silica provides insight into its prospective opportunities for industrial applicat ions. The results show that the hydrothermal reaction hardly affected the l ocal silicate structures within the temperature range tested, < 240 degrees C. Regarding the Si local structure, not only Q4 [*Si(OSi)(4)] but also Q2 [(OH)(2)*Si(OSi)(2)] and Q3 [(OH)*Si(OSi)(3)] units were observed in the ho t-water-treatment residues, whereas it is known that rice husk ash consists of only Q4 units. This suggests a possible utilization of the hot-water-tr eatment residue different from that of rice husk ash. Incidentally, some po rtion of the silica dissolved in the aqueous phase, affecting the apparent XRD crystallinity but sustaining amorphous structures. The metallic impurit y level of the solid phase was remarkably lowered because of dissolution of the coexisting metals.