School of Environmental Science and Engineering, Shanghai Jiao Tong University, No. 800, Dongchuan Rd., Shanghai 200240, China.
J Hazard Mater. 2012 Sep 15;231-232:57-63. doi: 10.1016/j.jhazmat.2012.06.035. Epub 2012 Jun 26.
The aim of this study was to examine the adsorption capability and mechanism of hexadecyltrimethylammonium modified zeolite, which was synthesized from coal fly ash, for the removal of ionizable phenolic compounds (phenol, p-chlorophenol and bisphenol A, with different pK(a)) and non-ionizable organic compounds (aniline, nitrobenzene, and naphthalene, with different hydrophobicity). The obtained zeolite was identified as type Na-P1 (Na(6)Al(6)Si(10)O(32)·12H(2)O, JCPDS code 39-0219), which is classified into the gismondine group with a pore size of 3.1 Å × 4.5 Å [100] and 2.8 Å × 4.8 Å [101]. The adsorption of the two kinds of organic compounds was due to loaded surfactant bilayer because modified zeolite showed great ability for the removal of organic chemicals while little adsorption by zeolite was observed. The isotherm data of ionizable compounds fitted well to the Langmuir model but those of non-ionizable chemicals followed a linear equation. Uptake of ionizable compounds depended greatly on pH, increasing at alkaline pH conditions. In contrary, adsorption of non-ionizable chemicals was essentially the same at all pH levels studied. The adsorption of both kinds of organic compounds correlated well to k(ow) value, suggesting that more hydrophobic organic contaminants are more easily retained by modified zeolite. Based on the different adsorption behavior, the uptake of non-ionizable pollutants was thought to be a single partitioning process into the surfactant bilayer. For ionizable compounds, however, interaction of the phenol group(s) with the positively charged "head" of surfactant additionally functions.
本研究旨在考察十六烷基三甲基铵改性沸石（由粉煤灰合成）对可离子化酚类化合物（苯酚、对氯苯酚和双酚 A，具有不同的 pK(a)）和非离子化有机化合物（苯胺、硝基苯和萘，具有不同的疏水性）的吸附能力和机制。所得沸石被鉴定为 Na-P1 型（Na(6)Al(6)Si(10)O(32)·12H(2)O，JCPDS 编号 39-0219），属于 gismondine 组，孔径为 3.1 Å×4.5 Å [100]和 2.8 Å×4.8 Å [101]。两种有机化合物的吸附是由于负载的表面活性剂双层引起的，因为改性沸石对去除有机化学品具有很强的能力，而沸石本身几乎没有吸附作用。可离子化化合物的等温线数据很好地符合朗缪尔模型，但非离子化化学品的等温线数据遵循线性方程。可离子化化合物的吸收强烈依赖于 pH 值，在碱性 pH 条件下增加。相反，在研究的所有 pH 水平下，非离子化化学品的吸附基本相同。两种有机化合物的吸附都与 k(ow) 值密切相关，表明疏水性更强的有机污染物更容易被改性沸石保留。基于不同的吸附行为，认为非离子污染物的吸收是单一的分配过程进入表面活性剂双层。然而，对于可离子化化合物，酚基团与带正电荷的“头”之间的相互作用另外起作用。
