Assessment of adsorption kinetics for removal potential of Crystal Violet dye from aqueous solutions using Moroccan pyrophyllite

Abstract

This study involves the adsorption of Crystal Violet (CV) dye adsorbed from solution on the pyrophyllite's surface. The batch technique was used under a variety of conditions to produce quantitative adsorption, namely amount of adsorbent, dye concentration, contact time, pH solution and temperature. The maximum adsorption capacity of Crystal Violet on pyrophyllite was 9.58 mg/g for 10 mg/L of CV concentration, pH = 6.8 at a temperature 20°C and 1 g/L of adsorbent. This study of adsorption kinetics was carried out within framework of three models: intraparticle diffusion, pseudo-first order and pseudo-second order. The experimental isotherm data were analyzed using Langmuir and Freundlich models. Different thermodynamic parameters have shown spontaneous reaction with endothermic nature (The estimated value for DG was À7.64 kJ/mol at 293 K). Various techniques for characterizing the adsorbent were applied including X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled by energy dispersive X-ray spectroscopy (EDX). In addition, the regenerated adsorbents technique was reused several times; this demonstrated an economical aspect of using pyrophyllite which underlines the re-use importance considering the material capacity to regenerate.

Physically Crosslinked Poly (Vinyl Alcohol)/Kappa-Carrageenan Hydrogels: Structure and Applications

“…For PVA, K/PVA 1:20 and K/PVA 1:6, the model that best fits the experimental kinetic data is the pseudo-second order over the entire contact time range, which is consistent with the findings from the reference literature for this type of dye and hydrogel sorbents [85]. The high determination coefficients for the pseudo-second-order model implies that the sharing or exchange of electrons between the polymer substrate and CV (for PVA) and the electrostatic interaction between the ionized chemical groups of κ-carrageenan and the organic cation of CV is the rate-controlling step.…”

“…The contact time data from Figure 9c was fitted against various kinetic models, such as pseudo-first order, pseudo-second-order, intra-particle diffusion, liquid film diffusion and Elovich. The significance of each model was not presented here; however, it can be consulted from the reference literature [84][85][86]. The equations of the kinetic models, the parameters of the equations and the determination coefficient indicating the goodness of the fit (R 2 ) are depicted in Table 6.…”

“…Parameters of the isotherm models fitted onto the experimental CV adsorption data. : rate constant of pseudo-first order kinetic (min −1 ), k 2 : second-order rate constant (g/mg min), k d : rate constant of intraparticle diffusion (mg/g min 1/2 ), C: intercept of intraparticle diffusion, k fd : liquid film diffusion rate coefficients (min −1 ), α: (mg/g min) and β: (g/mg) are the initial adsorption rate of the Elovich equation, respectively the desorption constant related to the extent of surface coverage and activation energy constant for sorption [85,86].…”

“…Based on this model, the sorption of CV on the hydrogels could be described as a three-step process: (1) the transport of CV from the boundary liquid film to the surface of the adsorbent (external film mass transfer); (2) the further transfer of CV from the surface of the adsorbate to the internal active binding sites (intraparticle diffusion); and (3) the interaction of CV with the active binding sites. The appropriateness of the Weber and Morris intra-particle diffusion model to describe the sorption kinetic in the early-time approximation is extensively described by other studies involving hydrogel or biomass-derived materials [85,86]. At longer contact times, the external mass transfer and dynamic equilibrium processes could also play an important role in CV sorption.…”

Batch mode for adsorption of crystal violet by cedar cone forest waste

“…It is highly toxic to mammalian cells; it is also non-biodegradable and persists in the environment for longer time. It is therefore very important to remove this dye from water and wastewater [2,10].…”