Bandosz Teresa J
Department of Chemistry, City College of New York, New York, NY 10031, USA.
J Colloid Interface Sci. 2002 Feb 1;246(1):1-20. doi: 10.1006/jcis.2001.7952.
Activated carbons of various origins (bituminous coal, wood, coconut shells, and peat) were studied as adsorbents of hydrogen sulfide. Before the experiments the surface of the adsorbents was characterized by using the sorption of nitrogen, Boehm and potentiometric titrations, thermal analysis, and FTIR. The adsorbents were chosen to differ in their surface areas, pore volumes, and surface acidities. To broaden the spectrum of surface acidity, carbons were oxidized by using nitric acid and ammonium persulfate. After hydrogen sulfide adsorption the species present on the surface were analyzed using thermal analysis, ion chromatography, and elemental analysis. The H(2)S breakthrough capacity tests showed that the performances of different carbons differ significantly. For a good performance of carbons as hydrogen sulfide adsorbents a proper combination of surface chemistry of carbon and porosity is needed. It was demonstrated that a more acidic environment promotes the formation of sulfur oxides and sulfuric acid despite yielding small H(2)S removal capacities. On the other hand, a basic environment favors the formation of elemental sulfur (sulfur radicals) and yields high capacities. The presence of a sufficient amount of water preadsorbed on the carbon surface to facilitate dissociation also plays an important role in the process of H(2)S adsorption/oxidation. The results showed that there is a critical value in carbon surface acidity, which when exceeded results in a negligible hydrogen sulfide breakthrough capacity. This is consistent with the mechanism of H(2)S adsorption on unmodified carbons, where the rate-limiting step is the reaction of adsorbed hydrogen sulfide ion with dissociatively adsorbed oxygen. When the acidity is expressed as pH, its value should be higher than 5 to ensure the effective removal of hydrogen sulfide from the gas phase. Study of carbon regeneration using water washing and heat treatment showed that the adsorbents can be regenerated to about 40% of their initial capacity.
研究了各种来源（烟煤、木材、椰壳和泥炭）的活性炭作为硫化氢吸附剂的性能。在实验前，通过氮气吸附、 Boehm滴定法、电位滴定法、热分析和傅里叶变换红外光谱（FTIR）对吸附剂的表面进行了表征。选择的吸附剂在表面积、孔体积和表面酸度方面存在差异。为了拓宽表面酸度范围，使用硝酸和过硫酸铵对活性炭进行了氧化处理。在硫化氢吸附后，利用热分析、离子色谱和元素分析对表面存在的物质进行了分析。硫化氢穿透容量测试表明，不同活性炭的性能差异显著。要使活性炭作为硫化氢吸附剂具有良好性能，需要碳的表面化学性质和孔隙率的适当组合。结果表明，尽管硫化氢去除能力较小，但酸性更强的环境会促进硫氧化物和硫酸的形成。另一方面，碱性环境有利于元素硫（硫自由基）的形成，并具有较高的容量。预先吸附在碳表面的足够量的水有助于解离，这在硫化氢吸附/氧化过程中也起着重要作用。结果表明，碳表面酸度存在一个临界值，超过该值会导致硫化氢穿透容量可忽略不计。这与未改性碳上硫化氢吸附的机理一致，其中限速步骤是吸附的硫化氢离子与解离吸附的氧的反应。当酸度用pH表示时，其值应高于5，以确保从气相中有效去除硫化氢。用水洗和热处理对碳进行再生的研究表明，吸附剂可以再生到其初始容量的约40%。
