Influence of Surface Properties on the Mechanism of H2S Removal by Alkaline Activated Carbons

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• 作者：Rong Yan ; Terence Chin ; Yuen Ling Ng ; Huiqi Duan ; David Tee Liang ; and Joo Hwa Tay
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：January 1, 2004
• 年：2004
• 卷：38
• 期：1
• 页码：316 - 323
• 全文大小：156K
• 年卷期：v.38,no.1(January 1, 2004)
• ISSN：1520-5851

文摘

Alkaline activated carbons are widely used as adsorbentsof hydrogen sulfide (H₂S), one of the major odorouscompounds arising from sewage treatment facilities.Although a number of studies have explored the effectsof various parameters, mechanisms of H₂S adsorption byalkaline carbons are not yet fully understood. The majordifficulty seems to lie in the fact that little is known withcertainty about the predominant reactions occurring on thecarbon surface. In this study, the surface properties ofalkaline activated carbons were systematically investigatedto further exploit and better understand the mechanismsof H₂S adsorption by alkaline activated carbons. Twocommercially available alkaline activated carbons and theirrepresentative exhausted samples (8 samples collectedat different height of the column after H₂S breakthroughtests) were studied. The 8 portions of the exhausted carbonwere used to represent the H₂S/carbon reaction process.The surface properties of both the original and theexhausted carbons were characterized using the sorptionof nitrogen (BET test), surface pH, Boehm titration,thermal and FTIR analysis. Porosity and surface areaprovide detailed information about the pore structure ofthe exhausted carbons with respect to the reaction extentfacilitating the understanding of potential pore blockages.Results of Boehm titration and FTIR both demonstratethe significant effects of surface functional groups, andidentification of oxidation products confirmed the differentmechanisms involved with the two carbons. From theDTG curves of thermal analysis, two well-defined peaksrepresenting two products of surface reactions (i.e., sulfurand sulfuric acid) were observed from the 8 exhaustedportions with gradually changing patterns coinciding withthe extent of the reaction. Surface pH values of theexhausted carbons show a clear trend of pH drop alongthe reaction extent, while pH around 2 was observed for thebottom of the bed indicating sulfuric acid as thepredominant products. Although both carbons are coal-based and of KOH impregnated type, performances of differentcarbons differ significantly. A correlation is well establishedto link the reaction extent with various surface properties.In summary, not only the homogeneous alkali impregnationand physical porosity but also the carbon surface chemistryare significant factors influencing the performances ofalkaline activated carbons as H₂S adsorbents.