The effect of oxidation on the surface chemistry of sulfur-containing carbons and their arsine adsorption capacity

Two carbons with different sulfur contents were prepared and oxidized either by heating in air or by chemical treatment. The samples were then tested as adsorbents of arsine in dynamic conditions at room temperature, both in dry conditions and in the presence of moisture. Chemical and structural features of the initial and arsine-exposed materials were analyzed by energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, sorption of nitrogen and sorption of water. It was found that oxygen- and sulfur-containing groups participate in arsine oxidation to arsenic tri- and pentoxide and/or in the formation of arsenic sulfides. This occurred either via activation of oxygen or a direct involvement of these groups in reactions with arsine. A very hydrophilic surface of sulfur-containing carbons, which causes the presence of adsorbed water, even in dry conditions, enhances arsine removal. On the other hand, in moist conditions water totally occupies the pore system blocking the catalytic action of the surface toward oxidation, which leads to a very limited or zero AsH3 adsorption capacity. (C) 2010 Elsevier Ltd. All rights reserved.