Removal Properties of Anionic Dye Eosin by Cetyltrimethylammonium Organo-Clays: The Effect of Counter-Ions and Regeneration Studies

Abstract

The organo-clays (OCs) were prepared by a cation exchange reaction between surfactant (cetyltrimethylammonium, C16TMA) from different counterions (Bromide, Chloride, and Hydroxide). The effect of the counterions was investigated on the physico-chemical properties of the prepared organo-clays. The highest uptake of organic cations (1.60 mmol/g) was achieved using cetyl trimethylammonium bromide solution and the lowest value (0.93 mmol/g) was obtained after modification with cetyl trimethylammonium hydroxide solution starting from the same initial ratio of mmol/g of clay greater than 2.40. The arrangement of C16TMA cations within the interlayer space was assumed to be perpendicular with a tilt angle of 32° to the plane of clay sheets instead of being parallel to the clay surface using C16TMAOH solution at the same ratio. Different techniques were used to characterize these materials. The thermal stability of these organ-clays was investigated using an in-situ X-ray diffraction (XRD) technique. The decomposition of the surfactant moiety occurred at temperatures higher than 215 °C and was accompanied with a shrinkage of the basal spacing value to 1.42 nm. These materials were applied in the removal of an acid dye “eosin.” The removed amount of eosin depended on the initial concentrations and the content of surfactants in the organo-clays. The removal of eosin was found to be an endothermic process. The maximum amount of 90 mg/g was achieved. The preheated treatment temperature of two selected OCs did affect the removal properties of eosin. A progressive reduction was observed at temperatures higher than 200 °C. The regeneration of spent OCs was studied and acceptable removal efficiency was maintained after 4 to 6 cycles depending on the used initial concentrations.

Waste Bricks Applied as Removal Agent of Basic Blue 41 from Aqueous Solutions: Base Treatment and Their Regeneration Efficiency

“…The removal process for basic blue 41 was performed as reported in previous studies [19,33]. A stock solution of 1000 mg/L was prepared by dissolving 1 gram of BB-41 solid dye into 1 liter of distilled water.…”

“…The thermodynamic parameters, such as standard Gibbs energy change (∆G • ), enthalpy change (∆H • ), and entropy change (∆S • ) are summarized in Table 3 and were determined as reported in a previous work [19]. These parameters provide further details on the spontaneity, feasibility, and sorbate-sorbent interactions during the of BB-41 removal process.…”

“…A number of regeneration methods were summarized and discussed in recent reviews [23,75]. In this study, a regeneration method was adopted with an efficient, eco-friendly, and easy to operate process, to reuse the spent waste bricks [19,76]. The treatment of fresh spent waste bricks was done after the first removal of basic blue 41 by a solution containing cobalt cations and an oxidant oxone.…”

“…These are called as organoclays. These organoclays have a lower thermal stability due to the decomposition of organic molecules in the range of 200 to 400 • C and were used for the removal of acidic dyes [19]. The pillaring process was proposed to modify the chemical composition and enhance the thermal stability of the starting clay minerals.…”

“…This study was carried out to test the hypothesis that the waste bricks obtained from different areas, using different clays, could affect their physiochemical properties and if the resulting waste materials would be effective in the removal of BB-41 in various conditions. The testing of regenerative capacity after the first BB-41 removal was investigated, using a friendly method to the environment [19]. The materials were characterized by different techniques before their use and to correlate these properties to the removal efficiency.…”