Interactions of Arsine with Nanoporous Carbons: Role of Heteroatoms in the Oxidation Process at Ambient Conditions

摘要

Two carbons obtained from polymers containing no ash and commercial wood based carbons, as received and modified with nitrogen, were tested as adsorbents of arsine in dynamic conditions at room temperature. The chemical and structural features of the initial and exhausted carbons were analyzed by energy dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyses, adsorption of nitrogen, and sorption of water. It was found that heteroatoms present on the surface of the carbons studied, namely oxygen, nitrogen, and sulfur, catalyze arsine oxidation mainly to arsenic tri- and pentoxide and/or in the formation of arsenic sulfides. When the surface has a high degree of hydrophilicity and water is present in the system it blocks these active centers resulting in the negligible arsine removal capacity. On the other hand, on a relatively hydrophobic surface with active nitrogen species arsine is adsorbed and oxidized to arsenic oxide. A small quantity of adsorbed water converts arsenic oxide to arsenic acid, which migrates to small pores releasing the centers for further adsorption and surface reactions. The process proceeds until all pores are filled/blocked, disallowing for further adsorption/reaction of arsine molecules.