Effect of natural organic substances on the surface and adsorptive properties of environmental black carbon (char): Attenuation of surface activity by humic and fulvic acids
Effect of natural organic substances on the surface and adsorptive properties of environmental black carbon (char): Attenuation of surface activity by humic and fulvic acids
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DOI：
10.1021/es061307m
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发表时间：
2006-12-15
影响因子：
11.4
通讯作者：
Lu, Yufeung
中科院分区：
文献类型：
--
作者：
Pignatello, Joseph J.;Kwon, Seokoon;Lu, Yufeung
黑碳（BC）在土壤和沉积物中污染物的有效性中起着潜在的重要作用。最近的证据表明，天然物质可能会减弱原始BC的高表面活性。研究了土壤胡敏酸（HA）和富里酸（FA）对人工合成木炭表面性质和有机物亲和性的影响。将炭粉悬浮在HA或FA溶液中，通过吸附、蒸发水分或与Al 3+共絮凝等方式负载有机物。选择这些处理来模拟环境暴露的初始和更高级阶段。共蒸发显着减少了N-2 Brunauer-Emmett-Teller的总表面积的焦炭，但只有适度的CO2累积表面积高达1.4 nm。腐殖酸在吸附态和共絮凝态对有机物吸附的抑制程度与其分子大小成正比，苯<萘<菲，1，2，4-三氯苯和菲。腐殖物质也增加了等温线的线性。我们提出的模型假设，腐殖物质被限制在外表面，它们作为孔阻塞剂或竞争吸附剂，这取决于温度和吸附物的大小。氮被阻止从内部孔隙空间由于硬度在77 K的腐殖酸链延伸到孔喉，给人为低的表面积。与以前的结果一起，这一发现表明，N-2可能无法检测到地质吸附剂中的BC微孔。在较高的温度下（CO2，273 K;有机物，293 K），腐殖酸链更灵活，可以进入内部孔隙。腐殖酸抑制吸附的反直觉的分子尺寸依赖性是由于孔中的分子筛效应，其中有机化合物可用的吸附空间越来越局限于外部位点。
Black carbon (BC) plays a potentially important role in the availability of pollutants in soils and sediments. Recent evidence points to the possible attenuation of the high surface activity of raw BC by natural substances. We studied the effects of soil humic (HA) and fulvic (FA) acids on the surface properties and affinity for organic compounds of synthesized wood charcoal. Char powder suspended in a solution of HA or FA was loaded with organic matter via adsorption, evaporation of the water, or coflocculation with Al3+. These treatments were chosen to simulate initial and more advanced stages of environmental exposure. Coevaporation dramatically reduced the N-2 Brunauer-Emmett-Teller total surface area of the char, but only moderately the CO2 cumulative surface area up to 1.4 nm. Organic compound adsorption was suppressed in proportion to molecular size, benzene < naphthalene < phenanthrene and 1,2,4-trichlorobenzene, phenanthrene, for humics in the adsorbed and coflocculated states, respectively. Humic substances also increased the linearity of the isotherms. The model we propose assumes that humic substances are restricted to the external surface where they act as pore blocking agents or competitive adsorbates, depending on the temperature and adsorbate size. Nitrogen is blocked from the internal pore space due to stiffness at 77 K of humic strands extending into pore throats, giving an artificially low surface area. Together with previous results, this finding indicates that N-2 may not detect BC microporosity in geosorbents. At higher temperatures (CO2, 273 K; organics, 293 K), humic strands are more flexible, allowing access to interior pores. The counterintuitive molecular size dependence of adsorption suppression by humics is due to a molecular sieving effect in pores in which the adsorption space available to the organic compound is more and more restricted to external sites.