Interaction of Chromate on Surfactant Modified Montmorillonite:  Breakthrough Curve Study in Fixed Bed Columns

Abstract

Interactions between chromate and surfactant modified montmorillonite at room temperature (25 °C) and different pHs (1−7) in aqueous solution in fixed bed columns have been studied. A series of column tests were performed to determine the breakthrough curves at different initial surfactant loadings (0.5−3 CEC) of the bed. The interlayer spacing increased with the surfactant loading from 14.2 to 40.5 Å. Experimental results of the column tests and the basal spacing of the column material showed that the adsorption of chromate onto the clay did not occur until the initial surfactant loading was beyond a critical concentration apparently enough to open the clay sheets for the entry of chromate species. The shapes of the breakthrough curves indicate that the chromate ions enter the interlamellar region only when the initial surfactant loadings are beyond 2 times the CEC of the clay. The amount of adsorbate increases proportionally with increasing bed depth. A simple two-parameter model originally introduced by Yoon and Nelson (Yoon, Y. H.; Nelson, J. H. Am. Ind. Hyg. Assoc. J. 1984, 45, 509) was used to calculate the breakthrough time. Chromate could be recovered completely by washing with ammonium hydroxide, and the column material was found to regain its capacity to adsorb repeatedly after simple acid wash.

A Meticulous Study on the Adsorption of Mercury as Tetrachloromercurate(II) Anion with Trioctylamine Modified Sodium Montmorillonite and Its Application to a Coal Fly Ash Sample

“…The sodium form of the montmorillonite clay was prepared from montmorillonite as described previously in the literature . An 8.6 mL volume of 0.02 mol of trioctylamine in 3 mol L –1 HCl medium was added to 4 g of the sodium montmorillonite suspended in 15 mL of acetone . The acidic medium ensures the protonation of trioctylamine thereby rendering the clay surface organophilic.…”

“…33 An 8.6 mL volume of 0.02 mol of trioctylamine in 3 mol L −1 HCl medium was added to 4 g of the sodium montmorillonite suspended in 15 mL of acetone. 34 The acidic medium ensures the protonation of trioctylamine thereby rendering the clay surface organophilic. Further, the contents were stirred magnetically for 10 h. The mixture was centrifuged and washed, and the centrifugate was verified to ascertain the presence of chloride ion by the silver nitrate test.…”

Effective Cr(VI) Removal from Simulated Groundwater through the Hydrotalcite-Derived Adsorbent

“…The breakthrough curves are similar to those using modified montmorillonite to remove chromate. 19 Based on the data in Figure 1, various breakthrough times (i.e., 5% breakthrough time (t 5 ), the 50% breakthrough time (τ), and the maximum contaminant level (MCL) breakthrough time (t MCL )), as well as the effective Cr(VI) adsorption amount (Q eff ) were extracted, as summarized in Table 1. Note that τ is almost proportional to the adsorbent amount (W) used in the column and is inversely proportional to the Cr(VI) concentration (C I ) However, in some cases (i.e., with less adsorbent used or at a higher influent concentration of Cr(VI)), the [Cr(VI)] value in the effluent was higher than the USEPA MCL (50 µg/L) (i.e., t MCL ) 0 h; see Table 1), because of the short residence time.…”

“…23,25 As a matter of fact, hydrotalcitelike compounds or their calcined derivatives have been noted to adsorb Cr(VI) in a reasonably high amount in the batch reactor. However, there are only fewer papers reporting the investigation of Cr removal through the column using other types of adsorbents, 5,11,19,26 and there seems to be no report regarding the column tests using hydrotalcite-like materials to remove chromate, which is crucial for the groundwater remediation through a permeable reactive barrier. 3 Therefore, we hypothesize that the calcined hydrotalcite-like compounds are also effective in removing Cr(VI) through intercalation in the column experiments.…”

Uptake of permanganate from aqueous environment by surfactant modified montmorillonite batch and fixed bed studies

“…The surface modifications with organic cations have been widely used in order to alter the surface properties of swelling clays to improve their adsorption ability (Mahadevaiah et al 2008). Quaternary ammonium salts such as hexadecyltrimethylammonium (HDTMA) bromides are known to swell smectite layers to different extents depending on their initial loading.…”