In this work, mesoporous geopolymer was synthesized using a novel and easy synthesis route employing metakaolin and rice husk ash as sources of silica and alumina, and soybean oil as a ...mesostructure-directing agent. For comparison purposes, a geopolymer sample was produced without the use of oil. The samples were characterized by Fourier transform infrared spectroscopy (FT–IR), X–ray diffraction (XRD), specific surface area, pore volume, average pore size, and pore size distribution (BET and BJH methods). The materials were tested to remove methyl violet 10B dye from aqueous solutions. The results showed that the mesoporous geopolymer presented adsorptive superior behavior compared to the geopolymer prepared without the use of oil, being attributed to its superior pore properties. The adsorption equilibrium was attained within 120min, and the maximum adsorption capacity of mesoporous geopolymer was 276.9mgg–1. Therefore, the mesoporous geopolymer prepared in this work comprises a potential adsorbent, presenting pore intrinsic properties that result in a high adsorption capacity.
•An activated carbon with a high surface area and outstanding dye adsorption properties was studied.•Dye adsorption isotherms were quantified at different temperatures.•Statistical physics model was ...used to attribute theoretical interpretation of dye adsorption mechanism.
An activated carbon with a high surface area and outstanding adsorption properties was prepared for dye removal from water. The new adsorbent was obtained from the chemical activation and pyrolysis of sodium carboxymethyl cellulose (CMC). This activated carbon was employed to analyze and characterize the adsorption mechanism of three dye molecules: methyl violet, allura red and congo red. Different characterization techniques and experimental adsorption isotherms quantified at different temperatures (25–45 °C) were utilized to interpret the dye adsorption mechanism. A double layer adsorption model was employed to estimate the steric and energetic parameters associated with the adsorption of these dye molecules. The modelling results provided the possible adsorption orientations of these dyes on adsorbent surfaces at different operating temperatures and the number of bonded dye molecules per functional group of this adsorbent was also analyzed. Calculated adsorption energies showed that both exothermic and endothermic processes were feasible for these dyes and physical forces were involved in the adsorption mechanism. Overall, this new adsorbent showed a competitive performance for dye removal in aqueous solution and can be a potential option for industrial applications.
•Phenol and 2-nitrophenol on a biopolymer derived biochar adsorbent was analyzed.•Theoretical analysis of phenol and 2-nitrophenol adsorption mechanisms was performed.•The role of adsorbate structure ...on tested adsorbents was theoretically explained.
In this paper, the adsorption of phenol and 2-nitrophenol on a biopolymer-based biochar in single and binary systems was investigated at 298–328 K and pH 5. Experimental results indicated that the adsorption capacities of phenol were significantly reduced from single to binary systems compared to those obtained for 2-nitrophenol. This experimental evidence suggested an antagonistic effect between both adsorbates generating an inhibitive adsorption. In terms of modeling analysis, the single and binary adsorption isotherms were well reproduced by monolayer and competitive monolayer statistical physics models, respectively. These two models showed that phenol and 2-nitrophenol molecules have been mainly docked with an inclined and horizontal positions in single and binary systems, respectively. A detailed analysis of the number of captured phenol (n1) and 2-nitrophenol (n2) molecules per site in the binary systems demonstrated that its corresponding evolution varied with a completely inverse way thus corroborating the inhibition effect between phenol and 2-nitrophenol molecules. The monolayer and competitive monolayer models were used to estimate two adsorption energies to characterize the single and binary adsorption mechanisms. The analysis of the energetic parameters suggested that the adsorption process was a physisorption. The interpretation of all monolayer and competitive monolayer model parameters provided new insights that contributed to understand the single and binary adsorption mechanisms of phenol and 2-nitrophenol molecules on tested adsorbent.
•Two new adsorbents were prepared for dye adsorption from aqueous solution.•Statistical physics modeling was performed to characterize dye adsorption mechanism.•Physical interactions were involved in ...the endothermic dye adsorption.•Dye adsorption capacities ranged from 281 to 632 mg/g.
Activated carbons were prepared from ashitaba waste and a walnut shell to study the adsorption mechanism of congo red and methylene blue dyes in aqueous solution. These adsorbents were characterized via XRD, FTIR and SEM techniques and the dye adsorption isotherms at three temperatures were quantified. A statistical physics model was applied to interpret the adsorption mechanism of tested dyes and adsorbents. Modeling results showed that these dyes were practically separated in the solution leading to an absence of the aggregation process. Adsorption orientations of dye molecules on the adsorbents changed depending on the temperature and nature of systems. The adsorption capacity of ashitaba waste activated carbon for the removal of congo red was significant thus indicating strong interactions between this dye and tested adsorbent. Calculated adsorption energy varied from 7.25 to 20.43 kJ/mol and they showed that the adsorption of both adsorbates occurred via physical interactions at different temperatures where the removal process was endothermic.
•Adsorption of three dyes brilliant blue, sunset yellow and tartrazine on chitosan was studied.•Adsorption mechanism was analyzed with a multilayer statistical physics model.•Adsorption was performed ...with a horizontal position of molecules on the chitosan surface.
This study reports the statistical physics modeling of the adsorption of three dyes brilliant blue (BB), sunset yellow (SY) and tartrazine (TT) on chitosan from aqueous solution. A multilayer statistical physics model was applied to understand the dye adsorption at different temperatures (i.e., 298–328 K) and pH 3. Modeling results showed that the adsorption was performed with a horizontal position of BB, SY, and TT molecules on the chitosan surface. Dye adsorption capacities ranged from 406.19 to 814.27 mg/g for BB, from 924.88 to 1432.98 mg/g for SY and from 611.27 to 1065.55 mg/g for TT, respectively. Overall, the chitosan showed the highest adsorption capacities for dye SY (Q0 (SY-chitosan) > Q0 (TT- chitosan) > Q0 (BB- chitosan)). The analysis of adsorption energies indicated that the removal of these dyes was an exothermic physisorption process, which could be governed by steric parameters according to the results obtained with the multilayer statistical physics model. This study contributes with new theoretical and experimental findings of the dye adsorption using natural polymers.
•Preparation and characterization of a novel adsorbent for dyes adsorption.•The adsorption was performed via a mixed orientation.•Chracterization of the dyes adsorption mechanism via adsorption ...energy.
Herein, a novel mountain soursop seeds powder (MSSP) adsorbent was employed to explore the adsorption mechanism of two relevant environmental pollutants: crystal violet CV and methylene blue MB. As a first assessment to investigate the adsorption mechanism and to analyze the performance of this adsorbent, the dye adsorption isotherms were measured at 298–328 K and pH 8. Experimental results demonstrated that this adsorbent was more effective to remove the CV dye compared to MB dye from aqueous solution, thus concluding that it could utilized for the treatment of dye polluted industrial effluents. To further interpret the adsorption mechanism and to obtain a new physicochemical vision, a successful phenomenological theoretical analysis via double layer adsorption model was detailed in this paper. At high equilibrium concentration, the adsorbed quantities at saturation were calculated and they followed this sequence: Qsat (CV-MSSP) > Qsat (MB-MSSP). This theoretical finding explained the highest adsorption for CV dye at different temperatures and characterized analytically its affinity for tested adsorbates. The geometry inclination of tested dyes on MSSP adsorbent surface was described in the paper by analyzing the bonded number of CV and MB dye molecules per site. It was demonstrated that these dyes were adsorbed via a mixed orientation. Based on the estimated concentrations at half-saturation, the calculated adsorption energies suggested that the adsorption of CV and MB on MSSP adsorbent was endothermic. A general analytical description of the dye adsorption mechanism showed that the density of receptor sites and adsorption energies followed the same trend as the adsorption capacity, then they can be considered as the factors that governed this separation process.
In this research, the solid-liquid adsorption systems for MSAC (PbFe
O
spinel-activated carbon)-phenol and pristine activated carbon-phenol were scrutinized from the thermodynamics and statistical ...physics (sta-phy) viewpoints. Experimental results indicated that MSAC composite outperformed pristine AC for the uptake of phenol from waste streams. By increasing the process temperature, the amount of phenol adsorbed onto both adsorbents, MSAC composite and pristine AC, decreased. Thermodynamic evaluations for MSAC demonstrated the spontaneous and exothermic characteristics of the adsorption process, while positive values of ΔG for pristine AC indicated a non-spontaneous process of phenol adsorption in all temperatures. In a mechanistic investigation, statistical physics modeling was applied to explore the responsible mechanism for phenol adsorption onto the MSAC composite and pristine AC. The single-layer model with one energy was the best model to describe the experimental data for both adsorbents. The adsorption energies of phenol onto both adsorbents were relatively smaller than 20 kJ/mol, indicating physical interactions. By increasing temperature from 298 to 358 K, the value of the absorbed amount of phenol onto the MSAC composite and pristine AC at saturation (Q
) decreased from 158.94 and 138.91 to 115.23 and 112.34 mg/g, respectively. Mechanistic studies confirm the significant role of metallic hydroxides in MSAC to facilitate the removal of phenol through a strong interaction with phenol molecules, as compared with pristine activated carbon.
•Characterization of magnetic geopolymer for dyes adsorption was performed.•Advanced modeling analysis was applied to analyze dye adsorption.•Interpretation of the dyes adsorption mechanism via ...statistical physics parameters.
A magnetic geopolymer (MG) was used as an effective adsorbent for water decolorization, in particular, for the removal of acid green (AG) and procion red (PR) from aqueous solutions. AG and PR dyes adsorption mechanism for this adsorbent was experimentally and theoretically characterized via the analysis and description of eight adsorption isotherms obtained at 298–328 K. Results showed that the AG dye was strongly adsorbed in comparison to PR dye. It was also concluded that the temperature showed a minor effect on the variation of the adsorption capacity for both dyes. An analytical double layer adsorption model was chosen to explain these experimental findings. This model contained theoretical parameters that can be utilized to understand the dyes adsorption mechanism. The temperature effect on all model parameters was analyzed concluding that this operating parameter had a minor effect on the number of accepted amount of AG and PR dyes per receptor site of MG adsorbent (n) and the density of receptor sites (Dm). The trends of parameters n and Dm led to a slightly variation of the adsorption capacity at saturation (Qsat = 2.n.Dm) as a function of temperature. Particularly, it was also concluded that AG and PR dyes retained their adsorption orientations on the magnetic geopolymer surface. Overall, it was established that the adsorption performance for the removal of AG dye could be associated to its short molecular size. Calculated adsorption energies varied from 18.55 to 29.14 kJ/mol and from 8.55 to 14.77 kJ/mol for the AG-GP and PR-GP systems, respectively. These adsorption energies indicated that physical interactions were involved during the adsorption mechanism of these water pollutants.
Abstract
A novel lead ferrite-magnetic activated carbon (lead ferrite-MAC) composite was developed using the chemical co-precipitation method. Instrumental analyses such as X-ray diffraction (XRD), ...scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis were performed to characterize adsorbent. The uptake of phenol from aqueous solutions using the developed adsorbent was compared to that of pristine activated carbon. The maximum adsorption capacity of lead ferrite-MAC composite (145.708 mg/g) was more than that of pristine activated carbon (116.606 mg/g) due to the metal hydroxides coated on activated carbon since they improve the retention of phenol on the available active sites of adsorbent and create an additional electrostatic interaction with the phenol adsorbate. Regarding the high value of the coefficient of determination (
R
2
) and adjusted determination coefficient (
R
2
adj
), coupled with the lower values of average relative error (
ARE
) and minimum squared error (
MSE
), it can be found that the isothermal data for the lead ferrite-MAC adsorbent were in agreement with the isotherm models of Redlich-Peterson and Langmuir. From the kinetic viewpoint, pseudo-second-order and linear driving force models explained the phenol adsorption data for both adsorbents. The reusability tests for lead ferrite-MAC composite revealed that after six cycles, 85% of the initial adsorption capacity was maintained. The developed adsorbent can be successfully applied to uptake phenol from aqueous solutions.
•Methylene blue adsorption on a biomass was analyzed via theoretical physics-based calculations.•Role of biomass functionalities for dye adsorption was explained.•DFT simulation characterized the ...interactions between the methylene blue andbiomass surface.•Experimental and theoretical findings of dye adsorption on lignocellulosic biomass ere reported.
The adsorption of the methylene blue on the biomass obtained from brazilian berries seeds was studied. Experimental adsorption data and results of the physicochemical characterization of the adsorbent besides theoretical physics-based calculations were utilized to understand the dye adsorption mechanism. A monolayer adsorption model was proposed to simulate the dye adsorption assuming an interaction adsorbent + adsorbate via two different functional groups on biomass surface. This statistical physics model calculated the number of bonded MB dye molecules and the saturated adsorption capacity for both functional groups at different temperatures. For instance, the values of n1 and n2 were 0.34 and 0.51 at 298 K thus indicating that MB molecules interacted via a horizontal adsorption orientation with two and three functional groups of biomass surface. Calculations based on statistical physics and density functional theory characterized the role and relevance of proposed functional groups on dye adsorption including its thermodynamic parameters. Results demonstrated that the hydrogen and oxygen functionalities of biomass surface were the main responsible functional groups for dye adsorption. Therefore, this paper reports new findings to understand the adsorption mechanism of dye molecules on lignocellulosic biomasses.
