Effects of cationic surfactants on the sorption of contaminants on birnessite
Date Issued
2014
Date
2014
Author(s)
Wang, Nan-Hui
Abstract
Birnessite is a layered manganese oxide mineral. The hydrated layer structure of birnessite allows for the cations transporting in the interlayer region. To enhance the sorption performance for the organic contaminants, birnessite needs to be first surface modified by organic moieties. Inserting hydrocarbon chain into layers can increase the interlayer distance and hydrophobic property, resulting in higher affinity toward organic substances. Cetyltrimethylammonium modified birnessite (CTMA-birnessite) is prepared by a simple hydrothermal method for removing benzoic acid and methyl orange.
The synthetic birnessite materials are characterized by a number of characterization techniques, including powder X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transforminfrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The results indicate that the prepared birnessite has a basal spacing of 0.71 nm and CTMA-birnessite has a basal spacing up to 3.28 nm. The relative contents of Mn(II), Mn(III) and Mn(IV) on the sample surfaces are about 22.1%, 56.4% and 21.5% for birnessite, and 9.5%, 62.4% and 28.1% for CTMA-birnessite.
The CTAB modified birnessite was used to remove benzoic acid and methyl orange in aqueous solution. CTMA-birnessite has a high removal efficiency of benzoic acid at pH 3, while the uptake of benzoic acid decreased with increasing pH values. The reaction rate of benzoic acid sorption increases with the incorporation of CTMA. The pseudo-second-order kinetic equation provides a good description of the benzoic acid and methyl orange sorption on CTMA-birnessite. Benzoic acid sorption on CTMA-birnessite was well interpreted by Henry isotherm model. Instead, methyl orange sorption on CTMA-birnessite was well interpreted by Freundlich isotherm model.
The results show that the modification of birnessite by intercalation of the surfactant can enhance the sorption capacity of manganese oxides. The intercalation of CTMA+ to birnessite will enhance the efficiency on the sorption of organic substances. The mechanism of benzoic acid or methyl orange partition to CTMA+ and adsorption on the birnessite surface were also proposed in this study.
Subjects
吸附
苯甲酸
甲基橙
界面活性劑
水鈉錳礦
Type
thesis
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