Yan Rong, Chin Terence, Ng Yuen Ling, Duan Huiqi, Liang David Tee, Tay Joo Hwa
Institute of Environmental Science and Engineering, Nanyang Technological University, Innovation Centre, Block 2, Unit 237, 18 Nanyang Drive, Singapore 637723.
Environ Sci Technol. 2004 Jan 1;38(1):316-23. doi: 10.1021/es0303992.
Alkaline activated carbons are widely used as adsorbents of hydrogen sulfide (H2S), one of the major odorous compounds arising from sewage treatment facilities. Although a number of studies have explored the effects of various parameters, mechanisms of H2S adsorption by alkaline carbons are not yet fully understood. The major difficulty seems to lie in the fact that little is known with certainty about the predominant reactions occurring on the carbon surface. In this study, the surface properties of alkaline activated carbons were systematically investigated to further exploit and better understand the mechanisms of H2S adsorption by alkaline activated carbons. Two commercially available alkaline activated carbons and their representative exhausted samples (8 samples collected at different height of the column after H2S breakthrough tests) were studied. The 8 portions of the exhausted carbon were used to represent the H2S/carbon reaction process. The surface properties of both the original and the exhausted carbons were characterized using the sorption of nitrogen (BET test), surface pH, Boehm titration, thermal and FTIR analysis. Porosity and surface area provide detailed information about the pore structure of the exhausted carbons with respect to the reaction extent facilitating the understanding of potential pore blockages. Results of Boehm titration and FTIR both demonstrate the significant effects of surface functional groups, and identification of oxidation products confirmed the different mechanisms involved with the two carbons. From the DTG curves of thermal analysis, two well-defined peaks representing two products of surface reactions (i.e., sulfur and sulfuric acid) were observed from the 8 exhausted portions with gradually changing patterns coinciding with the extent of the reaction. Surface pH values of the exhausted carbons show a clear trend of pH drop along the reaction extent, while pH around 2 was observed for the bottom of the bed indicating sulfuric acid as the predominant products. Although both carbons are coal-based and of KOH impregnated type, performances of different carbons differ significantly. A correlation is well established to link the reaction extent with various surface properties. In summary, not only the homogeneous alkali impregnation and physical porosity but also the carbon surface chemistry are significant factors influencing the performances of alkaline activated carbons as H2S adsorbents.
碱性活性炭被广泛用作硫化氢（H₂S）的吸附剂，硫化氢是污水处理设施产生的主要恶臭化合物之一。尽管许多研究探讨了各种参数的影响，但碱性碳吸附H₂S的机制尚未完全理解。主要困难似乎在于，对于在碳表面发生的主要反应，人们确切了解的很少。在本研究中，系统地研究了碱性活性炭的表面性质，以进一步开发并更好地理解碱性活性炭吸附H₂S的机制。研究了两种市售碱性活性炭及其代表性的耗尽样品（在H₂S穿透试验后在柱的不同高度收集的8个样品）。这8份耗尽的碳用于代表H₂S/碳反应过程。使用氮气吸附（BET测试）、表面pH、 Boehm滴定、热分析和FTIR分析对原始碳和耗尽碳的表面性质进行了表征。孔隙率和表面积提供了有关耗尽碳的孔结构相对于反应程度的详细信息，有助于理解潜在的孔堵塞。Boehm滴定和FTIR的结果都证明了表面官能团的显著影响，氧化产物的鉴定证实了两种碳所涉及的不同机制。从热分析的DTG曲线中，在8个耗尽部分中观察到两个明确的峰，代表表面反应的两种产物（即硫和硫酸），其模式逐渐变化，与反应程度一致。耗尽碳的表面pH值显示出沿反应程度pH下降的明显趋势，而在床底部观察到pH约为2，表明硫酸是主要产物。尽管两种碳都是煤基且为KOH浸渍型，但不同碳的性能差异显著。建立了良好的相关性，将反应程度与各种表面性质联系起来。总之，不仅均匀的碱浸渍和物理孔隙率，而且碳表面化学也是影响碱性活性炭作为H₂S吸附剂性能的重要因素。
