Investigation on the surface active sites variation of mineral dusts

Abstract

The paper analyzed the groups naked and the transformed of fibrous brucite, wollastonite, chrysotile asbestos, sepiolite, palygorskite, clinoptilolite, crocidolite and diatomaceous earth mineral dusts by using IR under acid and alkali etched, strong mechanical and polarized molecular interaction. The results show that the active site focuses on ends in stick dusts and on defects or hole edges in pipe dusts. The inside active sites of dusts play the main role in small molecular substance. The shape of dusts affects their distributions and densities of active sites. The strong mechanical and weak chemical force make the active site feature of minerals change, the powder process brings about more naked surface groups and more combined types. The dust activity relates to the type, contribution, and naked level of surface groups. The studied dust surface groups are mainly as follows: OH⁻, Mg(OH)⁻, Si-O-Si, Ca-O-Si, -Mg-OH₂,-Al(Si)-OH, -Mg(Ca)-OH₂, Ca-O,-Si···OH, Mg(Fe)-OH. Due to the difference of surface composition and structure, the minerals have a large disparity on activity and character of surface groups. The one side surface group of chrysotile layer is the same as fibrous brucite and stripped layer with more naked group. The fibrous sepiolite and palygorskite surface OH⁻ similar to crocidolite is naked with their surface structural defects and cleavage. The more development of mineral defects, the higher of OH⁻ (H₂O⁺) content, the main H₂O⁺ of clinoptilolite is partly transformed into H⁺, NH₄⁺ or OH⁻. The acid etched process may change OH⁻ concentration, distribution and increase the defects and porosity of mineral fiber surface. The alkali etched has no effect on Si-O, Si-OH etc. and destroyed Al-O, Al-OH⁻ acid site of sepiolite, palygorskite and clinoptilolite. Some surface groups of remnant differ from original dusts. The surface process of small polarized molecular or middle moleular’s branch may produce ionation and new coordinate bond, and change the active properties and level of original dusts, such as the porous minerals producing acid site may act as some assistance catalysis in biochemistry process.

Keywords

mineral dusts / surface group / active site

References

[1] SantarenJ, AlvarazA. Assessment of the health effects of mineral dusts[J]. Industrial Minerals, 1994, 319: 101-109

[2] Wen L, Laing W X, Zhang Z G, et al. The IR spectra of minerals(in Chinese) [M]. Chongqing University Press, 1988. 34–97.

[3] FengQ M, DongF Q, LiG W, et al.. Discussion the active features and their hardness of mineral fiber dusts[J]. Non-Metallic Minerals, 1998, 21(supplement): 50-54(in Chinese)

[4] Dong F Q, Wan P, Pan Z L, et al. Study on the applied mineralogy of fibrous brucite (in Chinese)[M]. Sichuan Science and Technology Press, 1997. 39–48.

[5] BlancoC. Infrared studied of surface acidity and reversible folding in palygorskite[J]. Clay & Clay Minerals, 1988, 36(4): 364-368

[6] Dong F Q, Wan P, Feng Q M, et al. Study on the surface active sites and their variation of mineral dusts[A]. PIECE’ 99[C]. Yamaguchi, Japan, 1999. 23.

[7] InagakiS, FukishimaY, DoiH, et al.. Pore size distribution and adsorption selectivity of sepiolite [J]. Clay Minerals, 1990, 25: 99-105