Fourier Transform Raman Spectroscopy of Sorbed HDTMA and the Mechanism of Chromate Sorption to Surfactant-Modified Clinoptilolite

Abstract

We examined sorption of the cationic surfactant hexadecyltrimethylammonium bromide (HDTMA) to clinoptilolite zeolite and the subsequent sorption of the chromate anion to surfactant-modified zeolite (SMZ). We used Fourier transform (FT) Raman spectroscopy and batch sorption methods to elucidate the structure of sorbed HDTMA and to determine the mechanisms of chromate sorption. At high HDTMA loading levels (above the zeolite's external cation exchange capacity, ECEC), the Raman spectra indicated that sorbed HDTMA was similar in conformation to solution micelles and, thus, may contain anion exchange sites. Sorbed HDTMA showed less structuring of tail groups and a decrease in head group hydration. At lower loadings, the sorbed HDTMA tail groups tended to have more disorder, similar to solution monomers. When HDTMA loading rates were greater than 100% of the ECEC, chromate sorbed onto SMZ with near-equivalent Br- counterion exchange. A peak in the Raman spectrum at 902 cm-1 indicated the presence of sorbed Cr2O7 2-, although no bulk solution oligomerized chromate species should have been present at a solution pH of 7. A 30 cm-1 shift in the ν1 peak for sorbed versus solution chromate may indicate that surface-enhanced Lewis acid−base interactions were responsible for some chromate sorption in addition to the predominant anion-exchange mechanism.

Adsorption characteristics of triclosan from aqueous solution onto cetylpyridinium bromide (CPB) modified zeolites

“…MB has been successfully applied on the determination of the cation exchange capacity for the mineral surfaces [21,22], based on its replacement character with the exchangeable cations. Furthermore, since MB is a large molecular like tert-butyl ammonium ion [23], it cannot penetrate into the zeolite pore spaces, resulting in the MB cations only can exchange with the external cations of zeolite. Therefore, the external cation exchange capacity (ECEC) of the natural zeolite could be measured by using the adsorption of MB, as a modification of the method proposed by Ming and Dixon [24].…”

Sorption Behavior of 4-Chlorophenol from Aqueous Solutions By a Surfactant-modified Mexican Zeolitic Rock in Batch and Fixed Bed Systems

“…It is well established that zeolites modified with quaternary ammonium salts such as HDTMA can substantially enhance the removal of inorganic oxianions and organic solutes from aqueous solutions (Bowman, Haggerty, Huddleston, Neel, & Flynn, 1995;Haggerty & Bowman, 1994;Li, Anghel, & Bowman, 1998;Sullivan, Hunter, & Bowman, 1998). In a previous work (Cortés-Martínez, Martínez-Miranda, Solache-Ríos, & García-Sosa, 2004) we evaluate the removal of cadmium from aqueous solutions by both the surfactant-modified and sodium zeolitic tuff used in this work, therefore, the aim of this paper was to evaluate this surfactant-modified zeolite for the removal of 4-chlorophenol in batch and column systems.…”

Use of Surface Modified Inorganic Nano Materials as Slow Release Nitrogen Fertilizer

“…The results of the Thin Layer Funnels Analytical Test clearly indicate that the hydrothermally synthesized material SZC and SZM modified with HDTMA and ADOD can be used as slow release formulations, due to their greater tendency to hold Bowman 1997, 1998;Sullivan et al 1998) the plant nutrients (nitrate) and also release them slowly. Unmodified zeolite releases around 25-35% of nitrate and phosphate after the first irrigation, whereas more than 55% of nutrients were leached out from control soil.…”