Synthesis and properties of polysiloxane xerogels containing tetrasulfide groups

• Published in: Russian journal of inorganic chemistry 2012-11, Vol.57 (11), p.1496-1501
• Main Authors: Nazarchuk, G. I., Mel’nik, I. V., Kozhara, L. I., Goncharik, V. P., Zub, Yu. L.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Physical Methods of Investigation
• ISSN: 0036-0236; 1531-8613
• DOI: 10.1134/S0036023612110095

Polysiloxane xerogels with a functional group content of 1.1–1.9 mmol/g have been obtained by the hydrolytic condensation of the alkoxysilanes Si(OC 2 H 5 ) 4 and [(C 2 H 5 O) 3 Si(CH 2 ) 3 S 2 ] 2 in the 2 : 1, 4 : 1, and 8 : 1 ratios. It has been demonstrated by 13 C and 29 Si CPMAS NMR spectroscopy that the xerogels have a polysiloxane framework with dipropyl tetrasulfide bridges, silanol groups, unhydrolyzed ethoxyl groups, and hydrogen-bonded water molecules on the surface. The xerogels have a porous structure. As the molar ratio of the reacting alkoxysilanes is increased in the above-specified range, the specific surface area of the xerogel increases (from 89 to 312 m 2 /kg) and the same is valid for other structure-adsorption characteristics. The synthesized polysiloxane xerogels readily sorb Hg 2+ from acidified solutions. Their static sorption capacity can be as high as 1.5 g Hg per gram of sorbent. However, in the course of time, the 1 : 1 complexes forming on the xerogel surface undergo transformations accompanied by the release of mercury sulfide and/or Hg 2+ reduction to mercury metal.