Reactive adsorption of hydrogen sulfide on visible light photoactive zinc (hydr)oxide/graphite oxide and zinc (hydr)oxychloride/graphite oxide composites

Abstract

Composites of zinc (hydr)oxide and graphite oxide (GO) with 2, 5, and 20wt.% of the GO component were obtained by precipitating zinc hydroxide from zinc chloride with dispersed GO present in the solution. The materials were evaluated as adsorbents of hydrogen sulfide at ambient conditions. The surface properties of the initial and exhausted samples were studied by FTIR, XRD, SEM/EDX, TEM, nitrogen adsorption, potentiometric titration, microcalorimetry, and thermal analysis. The adsorption capacity increases with an increase in the content of GO in the composites studied. The lower adsorption capacities measured for the samples with 2 and 5wt.% of graphite oxide are linked to the zinc (hydr)oxychlorides phase present in these composites. The heats of H2S adsorption on the zinc (hydr)oxide and its composites were measured in nitrogen and in air flow. The results indicate that highly energetic adsorption centers are formed on the composite surfaces. Exposure to visible light decreases the H2S adsorption capacity. This behavior is linked to photoactivity that leads to the reduction of the composite and formation of sulfur and sulfites/sulfates. These processes involve active centers, OH groups, which react with hydrogen sulfide.