Prediction of bisolute adsorption isotherms using single-component data for dye adsorption onto carbon

Competitive adsorption of Alizarin Red S and Bromocresol Green from aqueous solutions using brookite TiO2 nanoparticles: experimental and molecular dynamics simulation

In this work, the effective adsorption and the subsequent photodegradation activity, of TiO₂ brookite nanoparticles, for the removal of anionic dyes, namely, Alizarin Red S (ARS) and Bromocresol Green (BCG) were studied. Batch adsorption experiments were conducted to investigate the effect of both dyes' concentration, contact time, and temperature. Photodegradation experiments for the adsorbed dyes were achieved using ultraviolet light illumination (6 W, λ = 365 nm). The single adsorption isotherms were fitted to the Sips model. The binary adsorption isotherms were fitted using the Extended-Sips model. The results of adsorption isotherms showed that the estimated maximum adsorption uptakes in the binary system were around 140 mg g^-1 and 45.5 mg g^-1 for ARS and BCG, respectively. In terms of adsorption kinetics, the uptake toward ARS was faster than BCG molecules in which the equilibrium was obtained in 7 min for ARS, while it took 180 min for BCG. Moreover, the thermodynamics results showed that the adsorption process was spontaneous for both anionic dyes. All these macroscopic competitive adsorption results indicate high selectivity toward ARS molecules in the presence of BCG molecules. Additionally, the TiO₂ nanoparticles were successfully regenerated using UV irradiation. Moreover, molecular dynamics computational modeling was performed to understand the molecules' optimum coordination, TiO₂ geometry, adsorption selectivity, and binary solution adsorption energies. The simulation energies distribution exhibits lower adsorption energies for ARS in the range from - 628 to - 1046 [Formula: see text] for both single and binary systems. In addition to that, the water adsorption energy was found to be between - 42 and - 209 [Formula: see text].

Sustainable competitive adsorption of methylene blue and acid red 88 from synthetic wastewater using NiO and/or MgO silicate based nanosorbcats: experimental and computational modeling studies

The competitive adsorption of cationic and anionic model molecules; methylene blue (MB) and acid red 88 (AR88), respectively, in aqueous solutions onto NiO and/or MgO SBNs was studied. Adsorption isotherms, kinetics and pH effect were investigated in batch modes. Computational modeling was conducted on Acclerys Material Studio for MB and AR88 adsorption. pH study showed that the adsorption is strongly pH dependent, increases for MB while decreases for AR88 with increasing the pH from 4 to 11. Isotherm studies revealed that the Sips model was the best fit for both molecules in single cases, and thus the Extended-Sips model for the binary systems. The kinetics for the binary systems were well-described by the external mass transfer model; thus, film diffusion is the most dominant in the adsorption of both organic onto the SBNs. The adsorption uptakes in binary systems exceed 130 mg g⁻¹ for AR88 (167.7 MgO-SBNs, 132.93 NiO-SBNs, and 178.5 mg g⁻¹ NiO-MgO-SBN), while it reached an uptake of 76.2 MgO-SBNs, 81.5 NiO-SBNs, and 94.7 mg g⁻¹ NiO-MgO-SBNs for MB within the time needed to reach equilibrium (10 min). The adsorption of these two molecules in binary systems showed a synergistic effect onto the three types of SBNs, that enhanced the adsorption uptakes. Computational modeling confirmed the synergistic effect, the adsorption energy of binary systems was lower than that in single systems. Regeneration study was conducted over four adsorption cycles to confirm the sustainability of SBNs. They were stable under thermal oxidation at 400 °C, without any impact on the adsorption capacity.

Silica-based NiO and MgO nanosorbcats (SBNs) for competitive adsorption of methylene blue and acid red 88.

Adsorption Model for the Removal of Acid Dyes from Effluent by Bagasse Pith Using a Simplified Isotherm

The adsorption of two acid dyes, viz. Acid Red AR114 and Acid Blue AB25, on to bagasse pith, a waste material from the sugar cane industry, has been studied. Equilibrium isotherms and agitated batch contact time studies have been carried out. A mass-transfer model has been used based on a Langmuir-type isotherm at maximum saturation. This simple or pseudo-irreversible isotherm and the assumption of pore diffusion enables a pore diffusion mass-transfer model to theoretically predict the experimental concentration decay curves very rapidly.

A modified homogeneous surface diffusion model for the fixed-bed adsorption of 4,6-DMDBT on Ag–CeOx/TiO2–SiO2

The adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from diesel fuel using a fixed bed column was investigated.

Applicable models for multi-component adsorption of dyes: a review

Adsorption is one of the several techniques that has been successfully used for dyes removal. Since most industrial colored effluents contain several components including dyes, having a strong knowledge about the scope of competitive adsorption process is a powerful key to design an appropriate system. This is mainly because of the complexity brought about by the increasing number of parameters needed for process description which complicates not only the process modeling but also the experimental data collection. A multicomponent adsorption model should be based on fundamental soundness, speed, and simplicity of calculation. For such systems, competition will change the adsorbent-adsorbate attractions. Thus, there is major concern to develop an accurate and reliable method to predict dye adsorption behavior in multi-component systems. This article covers topics such as the theory of dyes adsorption in multi-component systems along with applicable models according to the consistent theories presented by researchers.

Revisiting the determination of langmuir parameters--application to tetrahydrothiophene adsorption onto activated carbon

The selection of a proper sorbent for a given application is a complex problem. The design and efficiency of adsorption processes require an equilibrium adsorption model. Linear transformation is one of the methods available to estimate the adjustable parameters of isotherm models but possesses limitations compared to nonlinear regressions. A different approach to calculate predicted equilibrium isotherm values leading to an alternative nonlinear regression is presented in this paper and compared with usual regression methods. Adsorption isotherm data of gaseous THT onto three activated carbon materials constitute an experimental basis for the discussion. Assessment of the goodness-of-fit of the Langmuir model is supported by different selected test functions. The new nonlinear approach did not obtain the best results for each test function, but raises questions about the inherent combined error in regression procedures.

Single and multicomponent equilibrium studies for the adsorption of acidic dyes on carbon from effluents

The ability of activated carbon to adsorb three acidic dyes, namely, Acid Blue 80 (AB80), Acid Red 114 (AR114), and Acid Yellow (AY117), from wastewater has been studied at 20 degrees C. The three single-component systems and the three binary equilibrium systems have been measured experimentally. The three single-component isotherms were analyzed using the Langmuir, Freundlich, Redlich-Peterson, and Sips equations. The Redlich-Peterson equation gave the lowest errors using the sum of the squares of the errors closely followed by the Sips and Langmuir equations; the Freundlich fits were significantly worse. The three bisolute experimental equilibrium sets of data were analyzed by incorporating the previous four single-component isotherm equations into the ideal adsorbed solution theory (IAST). The solution methods for each of the four isotherm equations are presented in the paper, and the predicted results for the three bisolute systems, using the four isotherm equations, are compared. For the three bisolute systems (AB80 + AR114, AB80 + AY117, and AR114 + AY117), the Redlich-Peterson isotherm gives the best correlation with the experimental isotherm data.

Film-pore diffusion model for the fixed-bed sorption of copper and cadmium ions onto bone char

The sorption of copper and cadmium ions onto bone char in single component systems has been studied using fixed-bed column adsorbers. The effects of solution flowrate, initial metal ion concentration and bone char particle size have been studied. A film-pore diffusion model has been developed to predict the fixed-bed breakthrough curves for the two metal ions. A sensitivity analysis has been carried out to investigate the influence of the external mass transfer coefficient (film resistance), the effective diffusion coefficient (pore diffusion) and the solid phase loading capacity. It is found that under the experimental conditions employed in the study, film diffusional resistance was low and the Biot numbers were relatively high. Furthermore, a constant effective pore diffusivity was not sufficient to correlate the breakthrough curves accurately and a variable dependent effective diffusivity was required; suggesting a possible contribution from surface diffusion. Since the metal ion-bone char systems take a long time to reach equilibrium, the solid phase loading capacity, as predicted by the "best-fit" equilibrium isotherm, was not suitable for use in the diffusional mass transport model and the mass balance solid phase loading was utilised instead.