Application of Organo-Magadiites for the Removal of Eosin Dye from Aqueous Solutions: Thermal Treatment and Regeneration

Abstract

Na-magadiite exchanged with cetyl-trimethylammonium cations provided organophilic silicate materials that allowed for the effective removal of the acidic dye “eosin”. The organic cations were intercalated into the interlayer spacing of the layered silicate via an exchange reaction between the organic cations from their bromide salt and the solid Na-magadiite at room temperature. Different techniques were used to characterize the effect of the initial concentration of the surfactant on the structure of the organo-magadiites. The C, H, and N analysis indicated that a maximum of organic cations of 0.97 mmol/g was achieved and was accompanied by an expansion of the basal spacing of 3.08 nm, with a tilted angle of 59° to the silicate layers. The conformation of the organic surfactants was probed using solid-state 13C, finding mainly the trans conformation similar to that of the starting cetyl trimethylammonium bromide salt (C16TMABr). Thermal gravimetric analysis was carried out to study the thermal stability of the resulting organo-magadiites. The intercalated surfactants started to decompose at 200 °C, with a mass loss percentage of 8% to 25%, depending on the initial loading of the surfactant, and was accompanied by a decrease of the basal spacing from 3.16 nm to 2.51 nm, as deduced from the in situ X-ray diffraction studies. At temperatures below 220 °C, an expansion of the basal spacing from 3.15 to 3.34 nm occurred. These materials were used as a removal agent for the anionic dye eosin. The maximum amount of the dye removed was related to the organic cation content and to the initial concentration of eosin, with an improvement from 2.5 mg/g to 80.65 mg/g. This value decreased when the organo-magadiite was preheated at temperatures above 200 °C. The regeneration tests indicated that an 85% removal efficiency was maintained after six cycles of use for the organo-magadiite using Ci of 200 mg/L.

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

“…This part indicated that the modification of the PG clay with surfactants has enhanced the removal of an acidic dye. Similar data were obtained using different organo-silicates [ 25 , 63 ].…”

“…As the C16TMA content increased, the removal amount was also improved due to the complete covering of the negative charge on PG clay by the surfactant, which means the electrical repulsion overcame [ 66 , 67 , 68 ]. Similar data were achieved using local clay mineral [ 32 ] and other silicate layered materials [ 25 , 63 ].…”

“…The intercalated C16TMA cations behave differently than the neat salt in the way that there was no increase of the basal spacing of the OCs in the range of 100 to 150 °C, which was reported for the C16TMABr salt. However, when other types of silicate were used as a host matrix, the intercalated C16TMA cations behave in the same way than the C16TMABr salt [ 25 , 63 ]. This fact could be related to an intrinsic effect of the type of silicate layers and its properties.…”

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

“…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.…”

Adsorption Process and Properties Analyses of a Pure Magadiite and a Modified Magadiite on Rhodamine-B from an Aqueous Solution

“…There are so many hydrated sodium ions between the plates that the cationexchange capacity (CEC) is higher than other silicates, such as montmorillonite and can reach up to 2.22 meq/g [8], which was determined from the ideal formulation of MAG (Na2Si14O29). So far, the cation-exchange properties of MAG investigated [9][10][11][12][13], indicate that MAG can be used as an adsorbent, based on cation exchange [14,15]. According to the current study, MAG can be synthesized [16][17][18][19][20][21]; the laminate of MAG was composed of SiO4 and has no other impurities.…”