Abstract:Azo dyes have been identified as the most toxic of all dyes since they may be converted into potentially carcinogenic and/or mutagenic amines as a result of the reductive cleavage of the azo linkages after being released into the aquatic environment. Azo dyes are extensively used in industries such as textile, paint, plastic, cosmetic and paper. The aim of the present work was to develop a clay-based methodology which could successfully be employed for the removal of dyes from aqueous solution. The adsorption … Show more
The purpose of this study was to determine whether a bentonite from the Gafsa deposit (western Tunisia) could be used to remove the Foron Blue 291 (FB) azo dye from wastewater. Batch adsorption and desorption experiments were conducted using untreated and purified bentonite and the influence of contact time, pH, adsorbent mass and temperature of the dye solution on the adsorption of FB was evaluated. Kinetic and isotherm data were fitted using two non-linear kinetic and two non-linear isotherm equations. In addition, the fits were evaluated using the coefficient of determination (R2) and the RMSE. The percentage of dye removal increased with increasing amount of adsorbent until total discolouration was achieved. The adsorption isotherms followed the Langmuir model, with the purified bentonite having a higher adsorption capacity than the raw material due to its higher specific surface area. In addition, the FB molecules were removed from the liquid medium by physical adsorption. Batch desorption experiments were conducted to study the desorption kinetics and the characteristics of the desorption isotherms as well as to quantify the portion of the FB (by mass) that was irreversibly fixed on the solid. Overall, the desorption kinetics were similar to the adsorption kinetics, which indicated that the adsorption-desorption process of azo dye is non-singular; irreversibility occurred that was underlined by an observed thermodynamic index of irreversibility (TII) of 0.69–0.94. The desorption isotherms of the FB depended on the mass of the FB that was initially adsorbed on the bentonite sample, suggesting hysteresis. The amount of irreversibly retained FB was between 46 and 68% of the initial adsorbed mass.
The purpose of this study was to determine whether a bentonite from the Gafsa deposit (western Tunisia) could be used to remove the Foron Blue 291 (FB) azo dye from wastewater. Batch adsorption and desorption experiments were conducted using untreated and purified bentonite and the influence of contact time, pH, adsorbent mass and temperature of the dye solution on the adsorption of FB was evaluated. Kinetic and isotherm data were fitted using two non-linear kinetic and two non-linear isotherm equations. In addition, the fits were evaluated using the coefficient of determination (R2) and the RMSE. The percentage of dye removal increased with increasing amount of adsorbent until total discolouration was achieved. The adsorption isotherms followed the Langmuir model, with the purified bentonite having a higher adsorption capacity than the raw material due to its higher specific surface area. In addition, the FB molecules were removed from the liquid medium by physical adsorption. Batch desorption experiments were conducted to study the desorption kinetics and the characteristics of the desorption isotherms as well as to quantify the portion of the FB (by mass) that was irreversibly fixed on the solid. Overall, the desorption kinetics were similar to the adsorption kinetics, which indicated that the adsorption-desorption process of azo dye is non-singular; irreversibility occurred that was underlined by an observed thermodynamic index of irreversibility (TII) of 0.69–0.94. The desorption isotherms of the FB depended on the mass of the FB that was initially adsorbed on the bentonite sample, suggesting hysteresis. The amount of irreversibly retained FB was between 46 and 68% of the initial adsorbed mass.
“…As shown in Figure 6, the pure Na-MMT shows absorption band at 1000 cm −1 , which corresponding to the Si–O stretching vibration of tetrahedral sheet, at 3615 and 1637 cm −1 are attributable to O–H stretching and bending vibrations from both the hydration water and the structural Si–OH, at 773 cm −1 corresponding to the Mg (Li)–(OH) vibration. All spectra display typical absorption bands of Na-MMT (Ren et al, 2013; Kaur et al, 2011). Figure 6.FT-IR spectrum of Na-MMT, DTHDB, and Na-MMT/DTHDB.…”
“…Modification using organic compound increases the interlayer height which makes the insertion of guest molecules [6]. OrganoMT can gener ally be obtained by intercalating cationic surfactants such as qua ternary ammonium compounds into the interlayer space through ion exchange process [7]. However, intercalation with quaternary ammonium salts containing long alkyl chain surfactants in the interlayer space is irreversible and prevents any further ionic ex changes which consequently limit the applications of the Orga noMT as new hybrid materials [8].…”
Short half-life and low bioavailability of Venlafaxine hydrochloride (VF), an
antidepressant drug, necessitates the frequent administration of VF tablets in a
day in order to maintain adequate drug concentration in blood plasma. This
generates the need for the development of formulations which could prolong the
release of VF and reduce the multiple dosages. The present work explores the
combination of Montmorillonite (Mt) with Pluronic F-68 (PF-68) (OrganoMT) for
oral delivery of VF. The effect of various parameters including pH of aqueous
drug solution, contact time and initial drug concentration on drug loading
capacity of OrganoMT has been studied. The synthesized OrganoMT-VF complexes
were characterized by various suitable techniques. XRD studies indicated that
the VF molecules were intercalated within the OrganoMT layers. In vitro release
behavior of VF from OrganoMT-VF complexes shows an extended-release pattern for
a period of 30 h and reaches upto 70% and 60% compared
to pure VF having complete release time of 5.5 h and 3.5 h in
simulated gastric and intestinal fluid respectively. Various kinetic models were
employed to elucidate the drug release mechanism where the best fitting was
obtained with Korsmeyer Peppas model. The results suggest the possibility of
designing an oral extended controlled release formulation for VF to minimize its
administration frequency thereby increasing the effectiveness of drug. This
improves patient compliance by reducing the dose from 4 times in 24 h to
once in 24 h.
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