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A new linear form analysis of Redlich–Peterson isotherm equation for the adsorptions of dyes
... For possible understanding of the MB removal process and prediction of the type of adsorption involved, adsorption data were modeled using kinetic, isothermal, and thermodynamic equations. Kinetic equations investigated were the pseudofirst-order [33], pseudo-second-order [34], Weber-Morris [35], and Elovich [36,37], while isothermal equations were the Langmuir [38], Freundlich [39], Dubinin-Radushkevich (D-R) [40], and Redlich Peterson (R-P) [41]. The linearized equations of the models are shown in Tables 1 and 2. Kinetic parameters: q t represents the amount of dye (mg g −1 ) adsorbed at time, t; k α (mg g −1 min −½ ), k 1 (min −1 ), and k 2 (g mg −1 min −1 ) denote the Weber-Morris rate constant, the pseudo-first-order rate constant and the pseudo-secondorder rate constant, respectively; α (mg g −1 min −1 ) represents initial adsorption rate; β stands for the desorption constant; and C represents intercept, which is associated with the thickness of the boundary layer. ...
... Linearized equation D-R constants, respectively; q mon and b RP are R-P isotherm constants, while α is an exponent variable that takes values between 0 and 1 [41]. All corresponding kinetics and isothermal parameters were determined from the intercept and slope of the plot of the appropriate equation. ...
... The model incorporates elements from both the Langmuir and Freundlich isotherm and has, therefore, found application in the description of both homogeneous and heterogeneous sorption systems [77]. In order to obtain the best linear fit that gave the highest R 2 value, the exponent variable, α, was assigned arbitrary values (ranging from 0.78 to 0.99), as earlier described [41]. Figure 9 (c, d) shows the plots of the R-P model. ...
This report describes the grafting of methacrylic acid (MAA) onto Garcinia kola pods (GKP) and its utilization in the sequestration of methylene blue (MB) and malachite green (MG) from aqueous medium. The synthesis method involved the use of a simple reactor containing N2 gas inlet and outlet. Free radicals were initiated by ammonium persulfate. With 2 g MAA, 33% grafting yield was obtained after 2 h, at 60 ℃, and with 0.01 mol L⁻¹ initiator. Material characterization was done by FTIR, SEM, XRD, and TGA, with all confirming the success of the grafting process. During the sorption process, solution pH, contact time, initial dye concentration, and temperature were varied. Rise in each of these parameters favored the sorption process up to their optimum states. With 0.1 g GKP-g-MAA, about 96% MB and 93% MG were removed. The adsorption process followed the pseudo-second-order kinetic model, while isothermal data fitted the Redlich-Peterson model best with R² values of 0.9994 and 0.9991 for the sorption of MB and MG, respectively. This was followed by Langmuir, indicating a homogeneous system and a reaction-controlled process. Thermodynamic data portrayed the sorption process as being feasible, spontaneous, endothermic, and characterized with increased disorderliness. Elovich model suggested the contribution of chemisorption; mean free energies, E ˂ 8 k Jmol⁻¹, indicated physisorption, while enthalpy change, ΔH°, depicted physisorption and the contribution of weak chemisorption in the sorption of MB and MG, respectively. Regeneration of the material was efficient, while high % dye removal showed a great adsorbent potential in the copolymer.
... As listed in Table 4, the adsorption process is spontaneous at all studied temperatures, as the value of ΔG0 is negative. The positive sign of ΔS0 means that the system has a good affinity of CV towards magnetic LCF adsorbent [33]. To evaluate the thermodynamic parameters, the ln (q e /C e ) was plotted against 1/T (K -1 ) for adsorption at different temperatures that range from 25 to 70 • C. The initial CV concentration (10 ppm) was constant with 0.025 g adsorbent, 5 min contact time, and pH 7. The ∆H 0 and ∆S 0 were determined from the trend line slope and intercept ( Figure 12). ...
... As listed in Table 4, the adsorption process is spontaneous at all studied temperatures, as the value of ∆G 0 is negative. The positive sign of ∆S 0 means that the system has a good affinity of CV towards magnetic LCF adsorbent [33]. ...
... However, the maximum CV removal (97%) occurs at solution pH 8. It is reported that the low pKa of the CV (0.8) and (5.3) leads to complete and facile ionization of this dye at almost all pH values and is present in the solution as cations [33,34]. Therefore, adjusting the pH solution to be higher than the pk a value is favorable in dye removal. ...
The presence of cationic dyes, even in a tiny amount, is harmful to aquatic life and pollutes the environment. Therefore, it is essential to remove these hazardous dyes to protect the life of marine creatures from these pollutants. In this research, crystal violet (CV) dye elimination was performed using a lignin copper ferrite (LCF) adsorbent. The adsorbent was synthesized and characterized using FTIR, Raman, SEM, EDX with mapping, and VSM, which proved the successful formation of magnetic LCF. Adsorption experiments were performed using different effective parameters. The highest adsorption potential (97%) was executed at mild operating conditions, with a 5 min contact time at room temperature and pH 8. The adsorption kinetic study utilized four kinetic models: first-order, second-order, intraparticle diffusion, and Elovich. The results revealed that the adsorption process complies with the pseudo-first-order with a maximum adsorption capacity of 34.129 mg/g, proving that the adsorption process mechanism is a physical adsorption process. Three isotherm models, Langmuir, Freundlich, and Temkin, were examined. The adsorption mechanism of CV onto LCF was also followed by the Langmuir and Freundlich models. The thermodynamic parameters were examined and revealed that the adsorption onto LCF was an exothermic process. It was proposed that the adsorption process is a spontaneous exothermic process. LCF appears to forcefully remove toxic CV dye from textile wastewater.
... Graficando log(qe) vs log(Ce) se puede determinar si la isoterma de Freundlich describe el proceso de adsorción (Wu et al., 2010). ...
... Freundlich. El mecanismo de adsorción no es híbrido y no se considera adsorción de monocapa ideal en este modelo (Wu et al., 2010). La ecuación RP se observa en la Ecuación 6. ...
... KR es la constante de equilibrio (L g -1 ). El símbolo αR es la constante de RP (L β mg -β ) y β es un exponente que varía de 0 a 1. Pero la forma más fácil de adaptar la ecuación anterior es linealizando, para que sea sencillo el graficar e interpretar datos (Wu et al., 2010). La linealización de la Ecuación 6 se presenta en la Ecuación 7. ...
For the development of this project, the aluminosilicate zeolite from Chihuahua state, Mexico was characterized and analyzed to see the performance in the adsorption of arsenic and cadmium simultaneously. The X ray characterization proved that the zeolite is a clinoptilolite with a heulandite structure. The BET test show possibility of reactivation and the SEM study demonstrate it is a porous material. The most favorable adsorption results are values of 1.015 mg g-1 and 1.345 mg g-1 of arsenic and cadmium respectively, obtained at a pH of 7, 3 grams of sorbent, and 50 mg L-1 of initial concentration of each metal. For the isotherm models, the most fit in the results is the Freundlich isotherm, explaining a heterogeneous multilayer surface adsorption. Even if the zeolite presents a capacity of adsorption of arsenic and cadmium, these can be improved with treatment.
The first treatment, zeolites were combined with HNO3 at different concentrations (3, 6 y 9 M) with a solid/solution ratio of 1:10. It was found that the zeolites treated with HNO3 have an improvement in the remotion of Cd reaching a 98% in the 3 concentrations, but suffer a decrease in the arsenic remotion reaching no more than 20%. An ANOVA analysis indicates there is no significant difference between the different concentrations of HNO3, but a significant difference with the natural zeolite.
Another treatment performed at the zeolite were using MgO and FeCl3 at high concentrations. The treatment with MgO had similar results at the realized with HNO3, while the treatment with FeCl3 was able to remove 100% of the two elements at a concentration of 10 mg L-1 each.
... When K RP and a RP are much higher than 1, Eqn (2) is transformed into the Freundlich model (Eqn (3)), with K F = K RP /a RP and n = (1 − g). 10,12,13 For example, Yu et al. 14 investigated the adsorption process of Congo red dye by organo-vermiculite at 35°C. The parameters (K RP , a RP , and g) of the Redlich-Peterson model (adj-R 2 = 0.9925) were 17 532 L g −1 , 148.3 (L mg −1 ) g , and 0.94, respectively; the corresponding values (K F and n) of the Freundlich model (adj-R 2 = 0.9915) were 115.06 (mg g −1 )/ (mg L −1 ) n and 0.065, respectively. ...
... Because there are still some uncertain references, only references with high reliability of the van't Hoff equation (r 2 > 0.7) were considered. This means that some references (i.e., No. 3,7,12,23,24,26,27,28,37,44, and 60 in Supporting Information, Table S5) were not used for further calculations and discussion. Two methods (linear and nonlinear) were applied to determine those parameters based on the van't Hoff equation. ...
The adsorption equilibrium constant of the Langmuir model (KL; L/mol) has been applied as the so‐called standard thermodynamic equilibrium constantKEqo for calculating the thermodynamic parameters (∆G°, ∆S°, and ∆H°) of adsorption process by using the van't Hoff equation. Some authors have (directly and indirectly) applied the constant KRP (L/kg) of the Redlich–Peterson model for such calculating. However, this is an incorrect application because the unit of KRP is not suitable (it is not equilibrium constant). Its new adsorption equilibrium constant Ke(RP) (L/mol) was revisited based on aRP (L/mol)g. In the literature, there is still uncertainty regarding the application of aRP asKEqo for calculating the thermodynamic parameters. Therefore, the present study aimed to evaluate the feasibility of applying Ke(RP) to calculate thermodynamic parameters using available literature data. The thermodynamic parameters obtained from Ke(RP) were compared to those from KL. A case study on using a biosorbent for adsorbing methylene blue dye at different temperatures was carried out to re‐verify the feasibility. The Redlich–Peterson model is only valid when its exponent is in a strict range (0 ≤ g ≤1). The Redlich–Peterson model (68%; 227 observations collected from 52 published papers) describe adsorption equilibrium datasets better than the Langmuir model. The negative values ΔG° obtained based on Ke(RP) (11.7–47.6 kJ/mol) were significantly different (p = 2.98×10–12) from those on KL (12.2–40.8 kJ/mol). The magnitudes of ΔH° obtained based on Ke(RP) were significant different (p< 0.05) those on KL; however, such difference did not affect conclusions on dominant mechanism adsorption (physical or chemical). The magnitude of ΔH° for chemisorption (involved in covalent bonds) is higher than 200 kJ/mol. For the case study, the ∆H° (kJ/mol) and ∆S° [J/(mol×K)] values calculated based on Ke(RP) (11.65 and 111.5) were similar to those on KL (11.34 and 110.4, respectively). New equilibrium constant Ke(RP) (L/mol) of the Redlich–Peterson model can be applied asKEqo for calculating the thermodynamic parameters (∆G°, ∆S°, and ∆H°) of adsorption process under some specific cases (i.e., F, H, and L‐shaped adsorption isotherms). The majority of the adsorption processes (98%) involve physical adsorption. This article is protected by copyright. All rights reserved.
... Various physical and chemical separation techniques have been proposed for the efficient removal of heavy metals from aqueous solutions. These include chemical precipitation, coagulation, bioremediation, membrane technologies, application of microorganisms and biomass, ion exchange, and adsorption (Gode and Pehlivan 2006;Wu et al. 2010;Landaburu-Aguirre et al. 2010). Among these techniques, adsorption processes are the most applied in the industries and have been widely studied because of their affordability and ease of use (Peng et al. 2017). ...
... adsorbed at equilibrium, respectively, and K RP (L g −1 ) and α(L/mg) β are the R-P isotherm constants. β also is a constant, determining whether the isotherm converts to Langmuir equation (β close to 1) or transforms to Henry's law equation (β close to 0) showing that Freundlich isotherm is more compatible with the adsorption process (Wu et al. 2010). D-R isotherm is a temperature-dependent model used to identify the chemical or physical nature of adsorption by the mean free adsorption energy (E) per molecule sorbate transferred to the surface of solid from an infinite distance. ...
The abundant release of toxic heavy metals into wastewater has been a serious threat to human health, aquatic environments, plants, and animals; thus, it is critical to purify wastewater of these pollutants through a proper treatment process. A novel hydrogel compound was synthesized using partially hydrolyzed polyacrylamide (PHPAm) and functionalized Fe3O4-coated magnetic nanoparticles (PHPAm/Fe3O4@SiO2-SH) that is efficient in removal of mercury and lead from wastewater. This new magnetic nanoadsorbent is characterized using scanning electron microscope, Fourier-transform infrared, thermogravimetric analysis, vibrating sample magnetometer, and energy-dispersive X-ray analysis. The central composite design under response surface methodology (CCD-RSM) was applied in designing the experiments to optimize the main parameters affecting the adsorption capacity: initial concentration (77.50 mg L⁻¹), pH (6.11 and 6.48), adsorbent dosage (25 mg), and contact time (115 and 106 min) for both Hg²⁺ and Pb²⁺ adsorption, respectively. Quadratic models were used for variable predictions and analysis of variance was applied to evaluate the statistical parameters and investigate the interactions of the variables. The high determination coefficient (R² 0.99) for both metals indicates a good correlation between actual and predicted response values. Additionally, thermodynamic modeling showed an endothermic and exothermic for Hg²⁺ and Pb²⁺, respectively, and also the spontaneous nature of both metals’ adsorption process within the temperature range of 288–318 K. Mercury and lead kinetic studies were in agreement with pseudo-second-order modeling, and the equilibrium results revealed that the Langmuir isotherm best fit the experimental data with maximum adsorption capacities of 256.41 and 227.27 (mg g⁻¹) for Hg²⁺ and Pb²⁺, respectively. Overall, PHPAm/Fe3O4@SiO2-SH is thought to have highly promising potential for investigating heavy metals in wastewater treatment, and will make important contributions to similar studies that may be conducted in the future.
... Due to their flexibility, it can be suitable for homogenous and heterogeneous adsorption systems [88]. The linear expression of Redlich-Peterson isotherm model is given by the Equation (14) [89]: ...
... If β = 1 (values that are close to 1), it approaches the Langmuir isotherm model because of low liquid-phase concentration. In the current study, the obtained values of β are 0.541 and 0.605 which is significantly greater than 0 that corresponds to the Langmuir equation [88,89,92]. This suggests that the values are in accordance with the Langmuir conditions. ...
The development of advanced materials for the removal of heavy metal ions is a never-ending quest of environmental remediation. In this study, a facile and cost-effective approach was employed to synthesize copper ferrite (CF) and copper ferrite/reduced graphene oxide (CG) by microwave assisted combustion method for potential removal of barium ions from aqueous medium. The physiochemical characterizations indicated the formation of magnetic nanocomposite with an average crystallite size of CF and CG is 32.4 and 30.3 nm and with specific surface area of 0.66 and 5.74 m2/g. The magnetic results possess multidomain microstructures with saturation magnetization of 37.11 and 33.84 emu/g for CF and CG. The adsorption studies prove that upon addition of rGO on the spherical spinel ferrite, the adsorption performance was greatly improved for CG nanocomposite when compared with the bare CF nanoparticles. The proposed magnetic adsorbent demonstrated a relatively high Ba2+ adsorption capacity of 161.6 mg·g-1 for CG nanocomposite when compared to 86.6 mg·g-1 for CF nanoparticles under optimum conditions ( pH = 7 ; T = 25 ° C ). The pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich models were fitted to the kinetic data, the yielded R 2 value of 0.9993 (PSO) for CF and 0.9994 (PSO) for CG which is greater than the other two models, which signify that the adsorption process is chemisorption. Thermodynamic studies show that barium adsorption using CF and CG adsorbents is endothermic. The as-fabricated CuFe2O4/rGO nanocomposite represents a propitious candidate for the removal of heavy metal ions from aqueous solutions.
... The adsorption isotherm of MB onto APOR fitting to Langmuir [56], Freundlich [57], Dubinin-Kaganer-Raduskavich (DKR) [58], Temkin [55,59,60], and Redlich and Peterson [61,62] models was performed, and different isotherm equations are presented in Table 4. ...
... Redlich-Peterson (RP) [62] using the residual root mean squares (RMSE), sum square error (SSE), and chi-square test (X 2 ) functions where RMSE is the widely applied technique to foretelling the optimum isotherm at low concentrations [67], SSE is one the most utilized error functions, which provides a good match and the best value when we get close to zero [68], while the nonlinear chi-square (X 2 test is useful to show if the experimental result matched the expected data; the X 2 is a parametric test based on the distribution of the difference from normal distribution, small values of chi-square test refer their resemblance, while a larger numbers refer to the difference of the empirical result [69]. Error function equations are listed in Table 6 and results are shown in Table 7. ...
... The adsorption isotherm of MB onto APOR fitting to Langmuir [56], Freundlich [57], Dubinin-Kaganer-Raduskavich (DKR) [58], Temkin [55,59,60], and Redlich and Peterson [61,62] models was performed, and different isotherm equations are presented in Table 4. ...
... Redlich-Peterson (RP) [62] using the residual root mean squares (RMSE), sum square error (SSE), and chi-square test (X 2 ) functions where RMSE is the widely applied technique to foretelling the optimum isotherm at low concentrations [67], SSE is one the most utilized error functions, which provides a good match and the best value when we get close to zero [68], while the nonlinear chi-square (X 2 test is useful to show if the experimental result matched the expected data; the X 2 is a parametric test based on the distribution of the difference from normal distribution, small values of chi-square test refer their resemblance, while a larger numbers refer to the difference of the empirical result [69]. Error function equations are listed in Table 6 and results are shown in Table 7. ...
A new activated adsorbent was produced from the debris of Posidonia oceanica rhizomes (POR). POR were activated in acetic acid and utilized as an eco-adsorbent for the removal of cationic dye methylene blue (MB) from saline solutions. The purified Posidonia oceanica rhizomes (PPOR) and its activated form (APOR) were characterized by elemental analysis, pH-metric titration, Fourier transformer infrared (FTIR), and surface area measurements, which inferred a remarkable activation of APOR. An enhancement in the free acidic sites was confirmed. The adsorption data obtained were analyzed using Langmuir, Freundlich, Temkin, Dubinin-Kaganer-Raduskavich (DKR), and Redlich and Peterson (RP) isotherm models. The obtained data from these isotherm models were tested using some error functions (residual root mean squares error (RMSE), sum square error (SSE), and chi-square test (X²) function). Temkin isotherm model was the best isotherm fits the experimental data of APOR. Kinetic data were evaluated by pseudo-first-order (PFO), pseudo-second-order (PSO), and intraparticle diffusion models. The adsorption rate was found to follow PSO model with a good correlation (R² = 0.999–1). A suggested, endothermic, multilayer, combined electrostatic and physical adsorption mechanism may be responsible for the removal of MB from water utilizing APOR. Adsorption is anticipated to start with chemisorption on active functional groups of adsorbent’s surface followed by physisorption of the subsequent layers through adsorbate–adsorbate interaction. The removal process was successfully applied for MB-spiked saline and brackish water with removal efficiencies of 51.7–97.2%. The results revealed that activated Posidonia oceanica rhizomes is a promising adsorbent for the removal of the methylene blue dye from real saline and brackish water with high removal efficiencies.
Graphical Abstract
... Redlich-Peterson [25][26][27] ln( A C e q e -1) = g ln( C e ) + ln B ...
The focus of this research is to apply the selected error function equation to establish the equilibrium isotherm model that best describes the adsorption of Pb2+ and Mn2+ onto acid-activated shale. Data collected from the batch experiment were analyzed using selected isotherm models (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Sips and Redlich-Peterson). To compute the isotherm parameters used in choosing the best-fit isotherm model, selected non-linear error functions, namely, error sum of the square, normalized standard deviation, hybrid error function, root mean square error and Marquardt’s percent standard deviation were employed. From the scanning electron microscope results, it was observed that the surface characteristics of the shale change considerably with calcination and acid treatment but the acid-treated shale shows better uneven porous surface characteristics. Error function computation shows that the Dubinin-Radushkevich isotherm model had the least sum of normalized error of 0.3623 for Pb2+ adsorption and 0.5465 for Mn2+ adsorption; hence, it was selected as the best isotherm model for explaining the sorption of Pb(II) and Mn(II) ions unto acid-activated shale.
... Belhachemi and Addoun (2011) reported that threeparameter equations (Redlich -Peterson, and Sips) showed more applicability than the two-parameter Freundlich and Langmuir isotherms and that the Redlich -Peterson achieved the best fit. Again, Wu et al. (2010) noted that thirty papers reported the Redlich -Peterson was more accurate in describing adsorption systems than the Langmuir and Freundlich isotherms. With the shape parameter K l , the Langmuir model helps understand the nonlinear effect on the contaminant distribution in an aquifer (Landage and Keshari 2016). ...
Sorption is a necessary process influencing the subsurface solute or contaminant transport. There are many adsorption isotherms, and selecting one to represent the system is likely to remain an elusive goal. Also, the lack of observed data and its associated certainty may hinder the determination of sorption parameters. This study investigated the influence of different isotherms – linear adsorption assumption, Freundlich isotherm, Langmuir isotherm, and Redlich – Peterson isotherm, on chloride concentrations. The numerical model also gauged the extent of recharged waters migrating from the injection well. Temporal analysis of groundwater resident volumes helped to understand better the change in chloride concentrations with the selected isotherm. The residual solute concentrations from the isotherms followed the order: Redlich – Peterson < Freundlich < Langmuir. The results highlighted the importance of obtaining a range of sorption values rather than a single value from one fitted isotherm for the productive aid in groundwater decision making.
... The Redlich -Peterson model incorporates features of both Langmuir and Freundlich equations. It can be described as follows (Hamdaoui and Naffrechoux, 2007;Wu et al., 2010): ...
The use of biosorption as a strategy for lowering the amount of pollution caused by heavy metals is particularly encouraging. In this investigation, a low-cost and efficient biosorbent, Inula Viscosa leaves were used to remove zinc ions (Zn2+) from synthetic wastewater. A Fourier transform infrared spectroscopy experiment, a scanning electron microscopy experiment, and an energy dispersive X-ray spectroscopy experiment were used to describe the support. Several different physicochemical factors, such as the beginning pH value, contact duration, initial zinc concentration, biosorbent dose, and temperature, were investigated in this study. When the Langmuir, Freundlich, Temkin, Toth, and Redlich-Peterson models were used to match the data from the Inula Viscosa leaves biosorption isotherms, it was found that the biosorption isotherms correspond most closely with the Langmuir isotherm. On the other hand, the kinetic biosorption process was investigated using pseudo-first-order (PFO), pseudo-second-order (PS2), and Elovich models. The PS2 model was the one that provided the most accurate description of the biosorption kinetics. The thermodynamics process shows the spontaneous and endothermic character of Zn2+ sorption on Inula Viscosa leaves, which also entails the participation of physical interactions. In addition, the atom-in-molecule analysis, density functional theory, and the conductor like screening model for real solvents, were used to investigate the relationship that exists between quantum calculations and experimental outcomes.
... . . . (Wu et al., 2010, Jahed et al., 2014 . . (Moussavi et al., 2013, Sathishkumar et al., 2009, Ada et al., 2009 . . ...
Organophosphate pesticides such as diazinon and fenitrotion are fat-soluble, so delayed
toxicity occurs if significant amounts of them are stored in adipose tissues. These insecticides have been classified by the World Health Organization (WHO) as class II, having a moderate hazard. Therefore the preparation and use of grafted β
cyclodextrin/thermo-sensitive polymer/modified Fe3O4/SiO2 nano-particles was investigated for the removal of fenitrothion and diazinon from aqueous solution. Modified MNPs were synthesized due to increase of removal efficiency and applicability in different condition. MNPs were synthesized and characterized by using FTIR, SEM, CHN, TGA, and TEM. The effect of some operational parameters, such as pH, adsorption isotherms, sorption kinetics, concentration, reusability, adsorption/desorption temperature, and ultrasound effect on desorption were examined. The results showed that the best sorption of pesticides on the MNPs-AGENVC-CD took place at 20 °C and optimum pH of 6. The initial concentration and nano-sorbent dosage were 100 mg/L and 0.01 g, respectively. The kinetic study showed that the best time for the pesticides sorption was
90 min. Also, the Pseudo-Second-Order model used fitted the adsorption kinetics well, thus exhibiting high correlation coefficients. Pesticides sorption capacity was found to be 34 and 29 mg/g. The equilibrium data of pesticides modified by the MNPs-sorbent were correctly shown by Langmuir, Freundlich, Redlich-Peterson, and Temkin models. The data was well-fitted to Langmuir equation. The findings showed that the proposed method was very impressive, providing a significant adsorption capacity, appropriate reusability and control functions along with temperature variations.
... The Redlich-Peterson isotherm describes the adsorption equilibrium over a wide concentration range and can be applied in either homogeneous or heterogeneous systems due to its versatility. The good agreement of experimental results with the Redlich-Peterson adsorption isotherm was also found for dyes' adsorption on mesoporous activated carbon prepared from pistachio shells with NaOH activation [43]. ...
Water hyacinth biomass was used for the synthesis of activated carbons in the process of chemical activation with H3PO4, followed by controlled carbonization. The study investigates the effect of various impregnation weight ratios of H3PO4 and dry hyacinth (0.5–3.0), as well as different carbonization temperatures (T = 400–800 °C), on the surface characteristics of the produced activated carbons (AC). The activated carbon obtained with an impregnation ratio of 1.5 and a carbonization temperature of 600 °C (1.5 AC/600) showed the highest values of specific surface area of 1421 m2 g−1, representing a selected adsorbent for metformin removal. The chosen sample was characterized by elemental analysis, adsorption–desorption isotherms of nitrogen at −196 °C, via FTIR spectroscopy and the SEM method. The modeling of the experimental adsorption data showed that metformin adsorption: (i) can be best described by the Langmuir isotherm model, with the value of qmax = 122.47 mg g−1; (ii) led the pseudo-second order kinetic model; and (iii) is a spontaneous (ΔG° = −3.44 kJ mol−1) and endothermic (ΔH° = 8.77 kJ mol−1) process. A desorption study has shown that 92% of metformin was successfully desorbed in the presence of a 0.1 MHCl/ethanol mixture (volume ratio 2:1). The recovery of the adsorbent of 84%, after five successive cycles, indicated that the 1.5 AC/600 has potential to be applied in the real systems for water treatment.
... The Redlich-Peterson isotherm contains three parameters and incorporates the features of the Langmuir and the Freundlich isotherms, and the mechanism of adsorption is a hybrid and does not follow ideal monolayer adsorption (Wu et al., 2010). The experimental data apparently fit the equation's model, but the values of some physical constants have negative values which has not a physical meaning. ...
In this work, we report the synthesis of a biobased hydrogel comprised of collagen, chitosan, and polyurethane for the removal of textile dyes. The adsorption capacity of this hydrogel was improved by adding a magnesium metal‐organic framework to the semi‐interpenetrating polymer matrix yielding a composite hydrogel. Removal of Bismarck Brown and Congo red was studied, and the experimental results fit Freundlich’s model. Both hydrogel formulations were tested for the removal of textiles dyes from wastewaters. The magnesium‐metal organic framework improved the efficiency of the biobased hydrogel for the removal of direct and mordant dyes reaching up to 89 ± 2 %. The composite hydrogel was tested for the removal of Congo Red in a fixed bed column observing the breakthrough point after 168 min. Also, a flocculant material was prepared from collagen and chitosan and was tested for the removal of direct red dye from wastewater removing up to 80 ± 1%. The pretreated wastewater by coagulation‐flocculation was treated by adsorption yielding a global removal efficiency of 99%. Finally, the studied hydrogels are potentially biodegradable being completely degraded by the proteolytic action after 22 days.
... This is not apparent in the linear fit where the correlation coefficients are significantly lower. The Redlich-Peterson model incorporates both Langmuir and Freundlich isotherms with the introduction of a third parameter that accurately measures the adsorption affinity [58]. It is known that the isotherm fits more towards the Langmuir model if β is close to unity, and in our case, the β value of 0.333 at 303 K indicates that the adsorption of boron was due to both Langmuir and Freundlich isotherms. ...
... Redlich-Peterson isotherm is used to correct the errors encountered in using Langmuir and Freundlich adsorption isotherm [42]. The model is actually the blend of Langmuir and Freundlich adsorption isotherms into one [24] [43]. The Redlich -Peterson isotherm modeling for the Cd 2+ sorption was also presented in Table 1. ...
Recently, the harmful impact of toxic metals in the aquatic environment cannot be over emphasized again. This work investigated the potential application of ginger root waste (GRW) to remove toxic cations (Cd2+ and Pb2+) from the aqueous medium. Batch adsorption examination was carried out as a function of sorbent dose, initial metal ion concentration, contact time, and temperature. The sorption equilibrium of the metal ions onto the GRW was subjected to Langmuir, Freundlich, Elovich and Redlich-Peterson isotherm models over concentration ranges of 10-50 mg/L. Sorption information was used for kinetic and thermodynamic modeling. The GRW materials before and after sorption was characterized using FTIR and SEM. Results showed higher removal percentage of Cd2+ over Pb2+ ions in all the factors studied. The Redlich – Peterson isotherm model affirmed that sorption of Cd2+ and Pb2+ occurred in a heterogenous surface of the sorbent which is strongly influenced by multiple micropores and caves. Kinetic studies revealed that the sorption was controlled through intra-particle diffusion model aided by surface and chemical reactions. Meanwhile, thermodynamic parameters indicated that the Cd2+ and Pb2+ sorption process was endothermic, however, non-spontaneous at temperature of 303 and 313 K. The FTIR and SEM data showed the evidence of successful sorption of the toxic cations on to the sorbent material.
... concentration increased from 0.5 mg/L to 3.0 mg/L. This was because a further increase in concentration beyond 0.5mg/L does not increase the sorption capacity of Ag-PET MPs due to the saturation of phenol molecules on the surface of the sorbent after the established equilibrium temperature (298 K)[31,[33][34][35]. Thus, the best performance of Ag-PET MPs was unarguably favored at low temperatures corresponding to 298 K, with a maximum phenol removal efficiency of 89 % recorded at 298 k.Similarly, for the Pr-PET MPs sorbent, the surface plot ofFig. ...
Optimization modeling and the interpretation of the adsorptive uptake of phenol from aqueous solution using pristine (Pr), modified (Mod-) and aged (Ag-) polyethylene terephthalate microplastics (PET MPs) as adsorbents at optimum conditions have been investigated. The surface morphology and functional groups of the MPs were evaluated using SEM and FTIR-ATR systems, while the surface area of the MPs was estimated using the Brunauer-Emmett Teller (BET) model. Experimentally determined optimization and Response Surface Methodology (RSM) were used to simulate and interpret the adsorption of phenol onto PET MPs, to determine the effects of four adsorption factors (contact-time, initial concentration, pH, and temperature) on the response (removal efficiency) using central composite design (CCD). The results showed that optimum operating conditions for the PET MPs adsorption of phenol from aqueous solution corresponds to contact-time of 77 minutes, 50 mg/L initial concentration, pH of 6, and temperature of 298 K respectively. The maximum removal efficiency of phenol ions under this operating condition was found to be 93.72%, 92.78% and 95.80% for Pr-PET MPs, Mod-PET MPs and Ag-PETMPs respectively. To understand the nature of the PET MPs sorption process, Redlich−Peterson (R-P), Elovich and Dubinin-Radushkevich (D-R) isotherms were employed. The results proved that, D-R model best fitted the PET MPs sorption process at 0.7214 ≤ R² ≤ 0.9043. Elovich model confirmed the performances of the PET MPs uptake of phenol ions occurred by physical and exothermic processes. Their adsorption capacities followed Pr-PET MPs (0.226 mg/g) > Ag-PET MPs (0.216 mg/g) > Mod-PET MPs (0.126 mg/g) respectively.
... En cuanto a propuestas de isotermas de tres parámetros, se tienen los modelos de Hill en 1946 (Farouq y Yousef, 2015), isoterma de Dubinin-Radushkevich (Vijayaraghavan et al., 2006), isoterma de Langmuir (Gasparik et al., 2012), isoterma de Redlich-Peterson (Wu et al., 2010), isoterma de Sips (Loganathan et al., 2015), isoterma de Toth (Keller y Staudt, 2005), isoterma de Khan (Amrhar et al., 2015), isoterma de Radke-Prausnitz (Radke y Prausnitz, 1972) y la isoterma de Koble-Corrigan (Koble y Corrigan, 1952). Las isotermas de cuatro términos, aunque pueden ser más precisas, requieren de más iteraciones para encontrar sus parámetros, aun así fueron revisadas; se inicia con la isoterma de Fritz-Schluender (Fritz y Schluender, 1974), isoterma de Baudu (Vijayaraghavan, 2015), isoterma de Weber-van Vliet (van Vliet et al., 1980), isoterma de Dubinin-Astakhov (Sartarelli et al., 2012) y la isoterma de Marczewski-Jaroniec (Sivarajasekar y Baskar, 2014); finalmente se tiene una de cinco parámetros, la isoterma de Fritz y Schluender (Hamdaoui y Naffrechoux, 2007). ...
El gas puede estar presente en la roca generadora, ya sea como gas libre en el medio poroso, gas libre en las fracturas naturales o gas que se encuentra adsorbido, el cual puede llegar a representar hasta el 85% del volumen total presente en el yacimiento. Diferentes cuestionamientos han sido generados por los profesionales de la industria de los hidrocarburos acerca de si todos los parámetros necesarios son considerados en la cuantificación del volumen de gas original in situ, con el fin de mitigar la incertidumbre en su estimación. El objetivo de esta investigación es estudiar los principales métodos y correlaciones empleados para cuantificar el gas adsorbido por la roca, para finalmente estimar el gas total. Para lo anterior, se estudiaron múltiples modelos de adsorción con información de la literatura, con el fin de determinar cuáles modelos presentaban menor desviación, con respecto a los datos de laboratorio. Así mismo, usando las características de la Formación La Luna en Colombia, se propone una analogía con el fin de estimar las posibles reservas de esta formación. Los resultados demostraron que los modelos con mayor número de parámetros involucrados presentan mejor ajuste con los datos de laboratorio, sin embargo, modelos como el de Langmuir de tres parámetros o el de Jovanović se acercaron en gran medida a los valores reales. Lo anterior garantiza un menor error en el cálculo del gas total.
... A = bq ml, where q ml is the adsorbent's maximum Langmuir adsorption capacity (mg/g), and when = 0 [16] reduces to Henry's equation, with 1/(1 + b) denoting Henry's constant. The linear form of the Redlich-Peterson isotherm is given by [17][18] [19][20]. ...
Recent industrial growth in India has caused large quantities of heavy metals including mercury, lead, zinc, copper, nickel, cadmium, and chromium to be released into the environment. As heavy metals are extremely toxic and non-biodegradable, it is extremely difficult to separate them from the atmosphere. Many research studies attempted to address the ability of the non-conventional absorbents in removing different types of wastewater pollutants. As a cost-effective alternative to conventional effluent treatment methods, Bio-sorption technology utilizes natural and agricultural waste materials as absorbents, which are relatively cheaper, sustainable, and abundant. The study concentrates on the capacity of rice husk and orange peel in extracting heavy metals from waste water. Adsorption tests has been carried out for different combinations of rice-husk and orange peel varying dosage, contact time, pH and mixing speed and optimal levels resulting in maximum removal efficiency levels are ascertained. To determine the efficiency of the adsorbents, Redlich-Peterson isotherms were constructed using different combinations of orange peel and rice-husk under varying conditions.
... This equation can be represented in a different form (Eq. 10), preserving the symbols of the parameters (Eq. 9) (Wu et al. 2010): ...
The environmental pollution by toxic Co(II) ions had a negative impact on living organisms and water resources. The amorphous Zr-Ca-Mg and Ti-Ca-Mg phosphates with varied Zr and Ti content with the mesoporous structure (A BET = 19-232 m 2 /g, V des. = 0.075-0.370 cm 3 /g, D des. = 6.2-10.9 nm) were synthesized. The effect of adsorbent chemical composition, the presence of competing ions (0.1-1.0 M NaCl and 0.01-0.1 M CaCl 2 backgrounds), and pH (3.0-7.0) of aqueous solution on adsorption removal of Co(II) ions by Zr-Ca-Mg and Ti-Ca-Mg phosphates was studied. The highest adsorption capacity of Zr-Ca-Mg-1 and Ti-Ca-Mg-1 samples reached 253.3 and 212.8 mg/g. The prepared adsorbents demonstrated high efficiency at pH in the range of 3.0-7.0 and the presence of 0.1-1.0 M NaCl and seawater with a salinity of 35.0 g/L backgrounds. The chemisorption and ion-exchange mechanisms of Co(II) ions removal for Zr-Ca-Mg and Ti-Ca-Mg phosphates were proposed. The adsorption isotherms were well fitted with Sips and Langmuir models that proved the heterogeneous nature of adsorption sites as well as assumed the monolayer adsorption that occurs at specific homogeneous sites within the adsorbent without any interaction between the adsorbed substances. The kinetic data was well described by the pseudo-second-order model that is suitable for chemisorption processes as liming adsorption stage. The presented results shown the prospects of developed adsorbents for the investigation of real wastewater treatment from heavy metal ions and liquid radioactive waste purification.
... In other words, boron adsorption using poly (S-VBC-NMDG) seems to obey the principles of both monolayer adsorption on the homogeneous surface and multilayer adsorption on the heterogeneous surface [88][89][90]. In this case, the Redlich-Peterson isotherm exponent (g) equals 0.749 which shows the deviation of this model from the Langmuir model (if g = 1, the Redlich-Peterson model will be the same as the Langmuir model) [51,91,92]. ...
Boron removal by novel sulfur-based boron selective adsorbent is herein reported. The sulfur-based polymer prepared by the inverse vulcanization of sulfur and 4-vinylbenzyl chloride (VBC) under optimized reaction conditions was used as a substrate and further functionalized by N-methyl-D-glucamine (NMDG) under optimized reaction conditions. Batch adsorption boron removal tests showed that a pH of 9 results in the highest adsorption capacity while an increase in the adsorbent dosage also showed a non-linear increase in the removal capacity. Acid and alkali regeneration of the used adsorbent showed 86% of its initial capacity after five cycles. The equilibrium isotherms of the adsorption were best fitted with the Redlich-Peterson model indicating that the boron adsorption obeys the principles of both monolayer and multilayer adsorption with a Langmuir maximum adsorption capacity of 7.186 mg/g. On the other hand, pseudo-second-order best fitted the adsorption kinetics meaning that chemisorption is the main controlling mechanism. The thermodynamic studies showed an endothermic spontaneous adsorption process with an increased randomness degree at the solid/liquid interface after the adsorption. The developed adsorbent is the first sulfur-rich polymer and selective boron adsorbent that can effectively reduce boron in water while also offering a considerably lower price due to utilizing the cheap and already available elemental sulfur.
... The Freundlich, Langmuir, and Redlich-Peterson models were used as equilibrium models (SI). If g is 1, the Redlich-Peterson model is reduced to the Langmuir model, and if a R C e g is much larger than 1, the Redlich-Peterson model will be deducted to the Freundlich model (Wu et al. 2010). Because the Redlich-Peterson model contains both Langmuir and Freundlich models, the Redlich-Peterson model would fit best if the adsorption response falls between the trends shown by both models (Belhachemi and Addoun, 2011). ...
In this study, we optimized and explored the effect of the conditions for synthesizing Fe-loaded food waste biochar (Fe@FWB) for Cr(VI) removal using the response surface methodology (RSM) and artificial neural network (ANN). The pyrolysis time, temperature, and Fe concentration were selected as the independent variables, and the Cr(VI) adsorption capacity of Fe@FWB was maximized. RSM analysis showed that the p-values of pyrolysis temperature and Fe concentration were less than 0.05, indicating that those variables were statically significant, while pyrolysis time was less significant due to its high p-value (0.2830). However, the ANN model results showed that the effect of pyrolysis time was more significant on Cr(VI) adsorption capacity than Fe concentration. The optimal conditions, determined by the RSM analysis with a lower sum of squared error than ANN analysis, were used to synthesize the optimized Fe@FWB (Fe@FWB-OPT) for Cr(VI) removal. From the equilibrium model fitting, the Langmuir model showed a better fit than the Freundlich model, while the Redlich–Peterson isotherm model overlapped. The Cr(VI) sorption capacity of Fe@FWB-OPT calculated from the Langmuir model was 377.71 mg/g, high enough to be competitive to other adsorbents. The kinetic Cr(VI) adsorption was well described by the pseudo-second-order and Elovich models. The XPS results showed that Cr adsorbed on the surface of Fe-FWB-OPT was present not only as Cr(VI) but also as Cr(III) by the reduction of Cr(VI). The results of Cr(VI) adsorption by varying the pH indicate that electrostatic attraction is a key adsorption mechanism.
... A plot of Q versus log Ce enables the determination of the isotherm constants a and b from intercept and slope of straight-line plot. The Redlich-Peterson isotherm [28] incorporates the features of Langmuir and Freundlich isotherms, which has a linear dependence on concentration in numerator and exponential function in the denominator. It can be expressed as follows. ...
Persistent organic pollutants (POPs) foul aquatic ecosystems. The remediation of these contaminants is essential to promote public health, environmental quality, and the economy. To solve this problem, the efficiency of nanomaterial adsorption capacity was applied in this study to find the best way to decrease the amount of these risky materials in the environment. Low amount of nano-alumina (<10 g) has been used in this research which is much less than previous techniques where of nanoparticle was used and effect of small amount of nano-alumina on several Malaysian residual soil properties such pH, Plastic index and CEC was investigated. In comparison with popular bioremediation method, this method is easier to use in the field, due to its shorter process which saves time and reduces cost. Experiments were conducted using batch adsorption procedures at different DDT concentrations, from10 to 60 mg/L. The amounts of nano-alumina were 0.25, 0.50, 0.75, 1.0, 2.0 and 10% of mass of soil. The adsorption of DDT solution onto the nano-alumina was also characterized by initial rapid adsorption, which gradually became constant within 16 hours. Results of this study indicated nano-alumina adsorbed up to 70% of DDT. Result show that the effect of nano-alumina on soil properties is very minor effect.
... The values of B and A T obtained from this model are presented in Table 4. One of the three-parameter isotherms used in the adsorption process is the Redlich-Peterson isotherm (Wu et al. 2010). According to the empirical data, the Redlich-Peterson isotherm for nitrate adsorption by SMRM and RM was developed. ...
This research aimed to develop a novel composite as a low-cost adsorbent for the removal of nitrate ion from aqueous solutions. The characterization of this composite (composition of red mud with dimethyldioctadecylammonium bromide (DDAB)) was performed by XRF, XRD, FTIR, and BET analyses. The most influential variables on nitrate adsorption, including contact time, solution acidity, adsorbent amount, and temperature were studied. The maximum amount of nitrate adsorbed onto the prepared adsorbent was obtained at pH 5.5 and contact time 30 min. The heterogeneous adsorption occurred during the uptake of nitrate. The results of kinetic study revealed that intra-particle diffusion was the major limitation for nitrate adsorption rate. The values of thermodynamic parameters illustrate the non-spontaneous, associative, and exothermic adsorption process. Increasing the temperature enhances the tendency of the process to non-spontaneously. Research on fixed-bed column has been done under different initial nitrate concentrations. The adsorption capacity of nitrate was increased with an increase in the initial concentration of nitrate. The results of column data were successfully explained using the Thomas and Yoon–Nelson models.
... The Freundlich, Langmuir, and Redlich-Peterson models were used as equilibrium models (SI). If g is 1, the Redlich-Peterson model is reduced to the Langmuir model, and if a R C e g is much larger than 1, the Redlich-Peterson model will be deducted to the Freundlich model(Wu et al. 2010). Because the Redlich-Peterson model contains both Langmuir and Freundlich models, the Redlich-Peterson model would t best if the adsorption response falls between the trends shown by both models (Belhachemi &Addoun 2011). ...
In this study, we optimized and explored the effect of the conditions for synthesizing Fe-loaded food waste biochar (Fe@FWB) for Cr(VI) removal using the response surface methodology (RSM) and artificial neural network (ANN). The pyrolysis time, temperature, and Fe concentration were selected as the independent variables, and the Cr(VI) adsorption capacity of Fe@FWB was maximized. RSM analysis showed that the p -values of pyrolysis temperature and Fe concentration were less than 0.05, indicating that those variables were statically significant, while pyrolysis time was less significant due to its high p -value (0.2830). However, the ANN model results showed that the effect of pyrolysis time was more significant on Cr(VI) adsorption capacity than Fe concentration. The optimal conditions, determined by the RSM analysis with a lower sum of squared error than ANN analysis, were used to synthesize the optimized Fe@FWB (Fe@FWB-OPT) for Cr(VI) removal. From the equilibrium model fitting, the Langmuir model showed a better fit than the Freundlich model, while the Redlich–Peterson isotherm model overlapped. The Cr(VI) sorption capacity of Fe@FWB-OPT calculated from the Langmuir model was 377.71 mg/g, high enough to be competitive to other adsorbents. The kinetic Cr(VI) adsorption was well described by the pseudo-second-order and Elovich models. The XPS results showed that Cr adsorbed on the surface of Fe-FWB-OPT was present not only as Cr(VI) but also as Cr(III) by the reduction of Cr(VI). The results of Cr(VI) adsorption by varying the pH indicate that electrostatic attraction is a key adsorption mechanism.
... The Redlich-Peterson isotherm is used to represent the adsorption equilibrium in a wide range of concentrations and can be applied in homogeneous and heterogeneous systems (Wu et al. 2010). The Sips isotherm is a combined form of Langmuir and Freundlich expressions deduced to predict the adsorption systems heterogeneous and circumvent the limitation of the concentration of increasing adsorbate associated with the Freundlich isotherm model. ...
Hexavalent chromium (Cr VI) has mutagenic and carcinogenic properties and causes severe health and environmental effects. The chromium’s adsorption equilibrium in aqueous media, its mechanisms, and different lignocellulosic wastes have been studied by many researchers. In this way, this paper provides a systematic, updated, and critical overview of Cr (IVI) adsorption by lignocellulosic waste adsorbent. Besides, analyzing the Cr (VI) problems in the aquatic environment addressed to lignocellulosic waste and its properties as adsorbent. Also, it was made a deep revision about important topics such as chemical regeneration and Cr (VI) recovery, characterization techniques, and interfering factors effects (e.g., pH, dosage). In addition, it was studied carefully the adsorption phenomena through several mathematical models of kinetics and isotherms and analyzed the thermodynamics results reported by an important number of research papers. Through this review, it was observed that the lignocellulosic wastes adsorption capacities usually range from 0.32 to 403.23 mg g−1, the adsorbent percentage removal after regenerating cycle ranged between 26.5 and 98.69%, and a greater performance of removing Cr (VI) occurs at pH range 1–6. The pseudo-second-order and Langmuir models were the models that presented the best adjustment of the experimental data for Cr (VI) adsorption, and the thermodynamic nature was spontaneous and endothermic for most cases. Further studies about lignocellulosic waste adsorbents lifecycle, stability, large-scale production, and production cost analysis are still necessary to determine the stability and efficacy of lignocellulosic wastes adsorbents in real effluent treatment.
... Wu et al. proposed an effective exponential linear equation that was suitable and accurate to fit with adsorption experimental data in compare to logarithmical linear equation of Redlich-Peterson isotherm. The proposed equation was used for predicting the behavior of three dyes adsorption on certain kinds of pistachio shell activated carbons, and its performance was appropriate (Wu et al., 2010). ...
Among numerous methods developed in purification and separation industries, the adsorption process has received considerable attention due to its inexpensive, facile, and eco-friendly nature. The importance of the adsorption process causes extraordinary endeavors for modeling the adsorption isotherms during the years; thus, myriads of research have been conducted and many reviews have been published. In this paper, we have attempted to gather the most widely used adsorption isotherms and their related definitions, along with examples of correlated work of the recent decade. In the present review, 37 adsorption isotherms with about 400 references have been collected from the research published in the period of 2010–2020. The adsorption isotherms utilized are alphabetically organized for ease of access. The parameters of each isotherm, as well as the applicable definitions, are presented in the table, in addition to being discussed in the text. Another table is provided for the practical use of researchers, featuring the usage of the related isotherms in peer-reviewed studies.
... The values of Q max and K L were calculated from the slope and intercept obtained by a linear plot of 1/q e versus 1/C e (Langmuir, 1918). The Redlich-Peterson isotherm is a three-parameter equation, which is expressed as follows (Wu et al., 2010): ...
Broiler litter is generated in large quantities as a waste by-product of chicken meat production. N may be lost from the litter and emitted from bird housing as gaseous NH3, which can be damaging to the environment and limit the recycling of a valuable nutrient. This study investigated the effect of lignite application rate (0, 5, 10, 15, 20%) on N loss from broiler litter in a static chamber laboratory incubation. Lignite was subsequently dewatered and subbituminous coal modified by aerobic thermal oxidation and their ammoniacal N adsorption potentials were characterised. In a second static chamber incubation, the capacity of these materials (applied at 20%) to reduce N loss from litter was investigated. Finally, their potential to directly reduce NH3 emissions was examined using a chamber acid trap system. This study showed that lignite reduced N loss when applied to litter at a rate ≥ 5%, with the amount of N retained increasing with increasing lignite application rate. Litter treated with 20% lignite retained 24% more N than untreated litter. Following aerobic thermal treatment, maximum ammoniacal N adsorption capacities of the materials were as follows: lignite > dewatered lignite > modified subbituminous coal > subbituminous coal. Despite inequalities in adsorption capacity, lignite, dewatered lignite and modified subbituminous coal reduced total N loss by 17.3, 18.2 and 18.4% and NH3 emissions by 41.6, 49.1 and 29.8%, respectively. This study demonstrates the potential of coal-based materials to reduce NH3 emissions from broiler litter and increase the nutrient value of waste by reducing N loss.
The existence of lead ions seriously affects the quality of many metal products in metallurgical enterprises. Currently, the various methods of lead-ion removal tried by researchers will affect valuable metals in the removal process, thus resulting in low economic efficiency. In this study, a novel metal-organic framework adsorbent (UiO-FHD) which efficiently and selectively captures lead ions is developed by introducing multiple ligands. The maximum adsorption capacity of lead ions is 433.15 mg/g at pH 5. The adsorption process accords with the pseudo-second-order kinetic and the Langmuir isotherm models at room temperature. Thermodynamic experiments indicate that the removal of Pb(II) is facilitated by appropriate temperature reduction. The performance tests indicate that UiO-FHD maintains a high removal rate of 90.35% for Pb(II) after four consecutive adsorption-desorption cycles. The distribution coefficient of lead ions (26.7 L/g) shows that UiO-FHD has excellent selective adsorption for lead ions. It is revealed that the chelation of the sulfhydryl groups and the electrostatic interaction of the hydroxyl groups are the dominant factors to improve the removal rate of Pb(II) by density functional theory calculations. This study clarifies the value of self-designed novel organic ligands in metal-organic framework materials that selectively capture heavy-metal ions.
As heavy metals are very noxious for health also known as one of the most poisonous classes of water contaminants. Typically, metal pollutants are non-biodegradable and impervious towards oxidants, heat, and light. Thus, it is a precisely demanding task to eliminate them from water to reduce water pollution. In current studies, the process of adsorption was employed for deracination of Zn and Fe with modified surface of natural material as an adsorbent. TiO2 NPs were synthesized by using leaf extract of Putranjiva roxburghii and its nanocomposites were made with the fish scale biomass. Prime conditions for proficient removal of zinc were recognized at pH = 4 and for iron at pH = 6 having an initial concentration 100 mg/L, adsorbent dose rate of 0.1 g and contact time 120 minutes. Thermodynamic study revealed that process was spontaneous, and exothermic, resulted in increase in entropy with rise in temperature. Adsorption process has been certified with different isotherm and kinetic models, where the experimental data was brought into being good agreement with pseudo second order (R2 = 0.986) and Freundlich isotherm (R2 = 0.993) as compared with other models. For characterization of synthesized adsorbents scanning electron microscopy, UV–visible spectroscopy and Fourier-transform Infrared spectroscopy, X-ray diffraction, and energy-dispersive X-ray were used. Average particle size of the adsorbent used ranged from 1 to 5 µm.
Engineered landfills are considered to be one of the best municipal solid waste (MSW) disposal technique due to its cost-effectiveness, efficiency, and large capacity. However, the continuous occurrence of several bioprocesses results in the generation of considerable quantity of leachates with high concentration of heavy metals in addition to other organic and inorganic compounds. Seepage of such leachates containing heavy metal ions contaminates nearby environment and ground which causes severe health problems and unhygienic environment for living beings. A well-designed liner acting as hydraulic barrier is needed to minimize or restrict the intrusion of leachates into the natural ground. The present study discusses the suitability of soil–bentonite mixture as a bottom liner material to minimize leachate migration in engineered landfills. The extensive experimental study is performed on emphasizing adsorption characteristics of soil–bentonite mixture when in contact with leachate of different concentrations and at varying durations. Variation in adsorption characteristics was assessed by using batch adsorption and column testing studies. Several adsorption isotherm models were utilized to fit the experimental data for varying presumptions to be taken into consideration for the considered clay liner-leachate interactions. Results revealed that Redlich–Peterson nonlinear model fits the experimental outcome more precisely as compared to other isotherm models.KeywordsClay linerHeavy metalAdsorptionIsotherm model
The present research article depicts the adsorptive denitrogenation of indole-containing model oil using cobalt-incorporated acid-activated carbon (Co-MAC). The active metal incorporated acetic acid-activated bio-sorbent showed a significant adsorption capacity for indole from model fuel oil than mere activated carbon. In a batch study, maximum 96% indole removal was achieved with an initial indole concentration of 500 mg/L, catalyst dose of 10 g/L, time of 4 h, and reaction temperature of 303 K. The non-linear regression analysis was opted to fit the experimental equilibrium data into various adsorption isotherms, including Langmuir, Freundlich, Temkin and Redlich, and Peterson. Thermodynamic parameters of adsorption were investigated, and the entropy and heat of adsorption change were determined to be 0.26 kJ/mol K and 57.31 kJ/mol, respectively. Besides, a plausible adsorption mechanism of indole was also explored.
In the present study, we reported the feasibility to exploit the low cost, and renewable biomass Anethum graveolens (AG) as adsorbent to remove Rhodamine B (RhB) dye from aqueous solutions. The capacity of A. graveolens to absorb the dye was investigated by using batch adsorption procedure with examination of different operational factors such as pH (2–10), stirring speed (100–400 ppm), adsorbent concentration (0.5–5 mg L−1) and the initial dye concentration (10–50 mg L−1). The RhB removal efficiency increased from ~ 63 to 95%, depending on the operating conditions; the optimal conditions are 300 rpm for stirring speed, 6 and 7 for pH, 3 g L−1 for biomass dosage and 10 mg L−1 for dye’s concentration. In order to estimate the equilibrium parameters, the experimental data were analyzed using the nonlinear forms of different kinetic models (pseudo-first order kinetic model, pseudo-second order kinetic model, Elovich and intra-particle diffusion models), also different isotherm models (Langmuir, Freundlich, Dubinine and Temkin models) were studied. The results indicated that the RhB sorption follows the pseudo second order model; under the optimum conditions, the maximum biosorption capacity (qmax) of AG was (52–56 mg g−1). Langmuir and Freundlich model could fit the data better than Dubinin–Radushkevich and Temkin models. Scanning electron microscopy (SEM–EDX), X-ray fluorescence, attenuated total reflectance and X-ray diffraction analyses have been used to evaluate the morphological changes and the mechanisms of dye interaction with biomass. The chemical modification of functional groups of biomass institute the major contribution of hydroxyl groups for effective dye decolorization through complexation and electrostatic interactions due to the interactions of dye molecules of RhB with the functional groups, of adsorbent such as OH, COOH, CN, and CH groups.
The potentially toxic electroneutral and small boron species in water have presented a major challenge in their removal using conventional membrane technologies. The facile functionalization of cellulose nanocrystals (CNCs) with amino-polyol was successfully demonstrated and resulted in essential hydroxyl and amine functional groups for strong interactions with boron. The maximum boron uptake by the amino-polyol CNC (AP-CNC) was determined to be 71.9 mg g⁻¹ at 303 K, and the sorbent nanomaterial was capable of reaching over 90 % of its adsorption capacity within 1 minute. The as-synthesized AP-CNC showed excellent boron removal performance between pH 7 and 9 due to the predominant di-complexation of boron with the vicinal diols and amines. Furthermore, the larger aggregate of the hyperbranched polymer allowed for more accessible chemisorption sites, which explains the ultrafast kinetics of boron uptake. In this form, the regenerable AP-CNC, which outperformed all other reported sorbent materials, can be useful as a nanofiller in membranes or in sorbent cartridges for water purification and desalination applications.
Alkali lignin (AL) has attracted great attention as a material for treating dye wastewater due to its low cost and environmental friendliness. However, the unique structure and aggregation characteristics of AL regarding the dye wastewater removal mechanism have not been systematically revealed. Here, the removal process of typical cationic dye contaminants (methylene blue, MB) from dye wastewater by AL at different pH was explored and the unique synergistic effect mechanism of adsorption and flocculation was revealed. With increasing pH, the removal rate initially increased and then decrease. With increasing MB concentration, the optimal pH value corresponding to the maximum adsorption rate increased regularly. Zeta potential and Fourier transform infrared spectroscopy (FTIR) showed that electrostatic and π–π interactions and hydrogen bonding consisted push-pull balance under the influence of pH. In addition, scanning electron microscopy (SEM), ultraviolet and visible spectrum (UV) and particle size analysis showed that the aggregate structure and synergistic mechanism changed with the solution pH and concentration. In the low concentration solution, adsorption dominated. While in the high concentration solution, flocculation dominated. The removal mechanism consisted of the synergy of adsorption and flocculation laying the foundation for the efficient and environmentally friendly treatment of dye wastewater by AL.
The discharge of harmful dyes in water bodies is a serious pollution problem, dangerous for the ecosystem’s equilibrium and human health. In this sense, the aim of this work was to determine the influence of electrolytes (NaCl, KCl, CaCl2 and MgCl2) in the adsorption of Reactive Blue BF-5G dye, the most common dye used in industrial process for fabric coloring, using bovine bone char as the adsorbent. The bovine bone char was characterized by pH of point of zero charge (pHPZC), N2 adsorption-desorption isotherms, Fourier transform-infrared spectroscopy (FT-IR) and X-ray diffractometry (XDR). The characterization revealed a mesoporous structure (pore mean diameter of 94 Å and SBET ∼107 m² g⁻¹) with negative charge distribution at the surface (pHPZC = 3.8). The adsorption experiments revealed that the presence of KCl enhanced the material adsorption capacity (qmax = 195 mg g⁻¹), that the Sips isotherm best fitted the experimental data (R² > 0.9 except for KCl solution) and the adsorption process was mono- and multilayered. The kinetic adsorption experiments indicated that the inorganic electrolytes increased the initial adsorption velocity and the data was best modelled by the surface diffusional model (SDM), implying a resistance (aqueous > CaCl2 > NaCl > MgCl2 > KCl) to mass transfer at the surface of the pores which, in turn, prevented the dye diffusion to the interior of the adsorbent (qe = 71 mg g⁻¹). Therefore, small quantities of KCl can be used to lower the mass transfer resistance and provide higher adsorption capacity with reduced time of operation, thus increasing the overall process efficiency.
Hexavalent chromium (Cr⁶⁺) is a carcinogenic pollutant found in different wastewater streams. The current study investigates the potential removal of Cr⁶⁺ from aqueous solutions by nitrogen-doped coconut granulated activated carbon (N-GAC). The raw GAC was chemically and thermally treated with urea (1:1 ratio) in an ethanol medium and calcined under nitrogen atmosphere at temperatures 400 °C and 600 °C. The optimized sample (N-GAC 400 °C) possessed a remarkable surface area (474.62 m²/g) while the chemical composition analysis revealed successful doping of nitrogen with no significant changes on the mesoporous morphology of the raw GAC. The adsorption studies revealed that Cr⁶⁺ adsorption capacity was higher for N-GAC 400 °C. The removal efficiency was significantly decreased with increasing the initial solution pH (optimum pH 2.2). The temperature has no significant effect on the adsorption capacity. The equilibrium experimental results were best fitted with Sips and Redlich-Peterson isotherm models with R² ≥ 0.987 with a maximum adsorption capacity of 15.15 mg/g. The kinetic data agreed with the pseudo 2nd order model (R² > 0.997). The isotherm and kinetic studies revealed that physisorption and chemisorption processes are involved in the removal process. The adsorption mechanism was mainly controlled by electrostatic interactions, ion exchange and reduction of Cr⁶⁺ to trivalent chromium mechanisms. Accordingly, the N-GAC can be considered a promising material for the adsorptive removal of heavy metals from water.
A novel metal-organic framework (MOF) UiO-66-TLA (UiO-66-Trimellitic Acid) was synthesized by one-pot method with trimellitic acid as modifier, which can effectively remove the basic dye Basic Blue 3 (BB3) in wastewater. Modification with carboxyl groups facilitates the adsorption of the cationic dye Basic Blue 3. The adsorption of BB3 by the modified UiO-66-TLA was significantly greater than that of its parent MOF. The adsorption capacity of the modified UiO-66-TLA for BB3 (234.23 mg g−1) was 93.2% higher than that of the original UiO-66-NH2 (121.24 mg g−1), this is closely related to the electrostatic interaction of -COOH in trimellitic acid. UiO-66-TLA was successfully synthesized as indicated by various characterization results. The adsorption kinetics conformed to the pseudo-second-order model, and the adsorption isotherm conformed to the Redlich-Peterson isotherm. This indicates that BB3 is a multi-parameter model of monolayer/multilayer arrangement on the adsorbent surface, and its rate-controlling step is chemisorption. The adsorption process was non-spontaneous and belonged to an endothermic reaction, in addition, it has great adsorption stability and regeneration The interaction of the modified UiO-66-TLA with BB3 was mainly affected by mechanisms, such as electrostatic interaction, π–π stacking as well as the abundant functional groups on UiO-66-TLA surface. These results demonstrate that UiO-66-TLA is an efficient, regenerable, water-stable material for the removal of BB3 in solution, with practical implications, suggesting its potential as a dye adsorbent.
Walnut shell was used as an adsorbent for adsorption of acetic acid. Batch experiments were conducted for adsorption equilibrium studies and kinetics by using walnut shell. Optimization of parameters like temperature, rotation, adsorbent dose and contact time were studied. Amount of acetic acid adsorbed was analyzed by titration. Equilibrium condition was investigated. Adsorption kinetics were tested for different models and found best suitable for intraparticle diffusion model. The batch experimental data was fitted to Langmuir, Freundlich, Temkin, Sips and Redlich-Peterson isotherms. The best fitted isotherm was Langmuir isotherm. Regeneration was tried by heating the adsorbent in microwave at 200 ºC. Up to three cycles adsorbent gave good efficiency for adsorption of acetic acid.
Phenol is a hazardous organic chemical that is introduced into the environment by industrial and pharmaceutical discharges. Bentonite can abort harmful substances in the environment and is widely used in the field of environmental geotechnical engineering. However, the adsorption effect of bentonite on organic pollutants is poor. At the same time, its permeability and expansion characteristics are easily affected by saline solution and acid aqueous solution. Biochar, as a simple and low-cost adsorbent, can effectively remove inorganic and organic pollutants. The purpose of this study is to prepare a composite material including biochar and bentonite, improve the removal efficiency of phenol and the impermeability of bentonite in saline and acidic aqueous solution. Adsorbents are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), flourier transform infrared spectroscopy (FTIR), and BET-N 2 . Permeability coefficients of bentonite and sugarcane biochar@bentonite(SuBC@Ben) are determined. Effects of bentonite, SuBC@Ben, and sugarcane biochar on the removal of phenol under different contact times, concentrations, pH, and temperature are studied. Results show that the change range of SuBC@Ben permeability coefficient is not obvious with the increase of saline solution concentration, indicating that SuBC@Ben has good impermeability in saline solution.
Synthesis of hollow spherical polyaniline (HSPANI) with the merits of facile strategy, low cost, low safety risk and high adsorption capacity of Cr(VI) is always a big challenge. In this manuscript, we proposed a facile way to preparation of HSPANI by using the poly(styrene‐co‐acrylic acid) sphere as template. The results indicated that HSPANI was emeraldine comprised of lots of basically uniform hollow spheres, and its average pore diameter was about 300 nm. HSPANI displayed high adsorption capacity of Cr(VI), and its value arrived at 601.3, 347.8, 235 mg g−1 at pH = 1, 2, and 3, respectively, which were high than many other adsorbents. The endothermic, spontaneous and chemical adsorption process was responsible for this adsorption. The Cr(VI) adsorption capacity was significant relied on its pH, contact time, Cr(VI) concentration and adsorption temperature. The adsorption behavior was well agreed with pseudo second‐order equation and Redlich–Peterson isotherm models. HSPANI exhibited remarkable selectivity for adsorption of Cr(VI) even if the K+, Cu2+, NO3− and SO42− were coexisted. HSPANI also displayed excellent regeneration performance. Therefore, this work not only provided a facile way to synthesis of hollow spherical polyaniline, but also supplied a potential adsorbent for adsorption of Cr(VI) from the industrial wastewater.
The host–guest β-cyclodextrin has attracted much attention for potential application in various fields due to its low price, natural pores, and functionality. Herein, we report a method using 1,4-phenylene diisocyanate (PPDI) to fabricate β-cyclodextrin (CD)-modified poly(chloromethyl styrene) (PCMS) resin, namely, [email protected] β-Cyclodextrin was utilized to improve the adsorption performance of PCMS, which was then applied to anchor β-cyclodextrin powder. The product exhibits excellent renewability and availability due to the application of PCMS. The adsorption performance was fully exerted by the combination of β-cyclodextrin and PCMS. SEM mapping, FTIR, TG, BET, and XPS analyses were conducted to explore the morphological and structural properties of [email protected] Adsorption experiments show that [email protected] removed 100% of TC and 75% of Cu(Ⅱ), and the maximum adsorption capacity for Cu(Ⅱ) and TC reached 187.6 and 266.4 mg g⁻¹, respectively. After recycling six times, the adsorption ability of Cu(Ⅱ) and TC still achieved excellent removal performance. In addition, the chelation of the lone N pair, the hydrophobicity of the cavity, H-bonding, complexation, n-π interaction, and porous structure showed the possible mechanism. We used computational formulas to simulate the adsorption state and found that the resin is theoretically feasible. Most importantly, we propose a novel application of [email protected] This work shows that the resulting [email protected] is highly efficient and can be easily recycled, making it an attractive resin for adsorption.
In the current investigation, bamboo leaves (BL), H2SO4 treated bamboo leaves (SBL), and H3PO4 treated bamboo leaves (PBL) were utilized as biosorbents for the elimination of Malachite Green (MG) from the synthetic medium. The adsorption study was executed under the variation of different experimental conditions like pH, biosorbent dosage, contact time, and the temperature on the MG. Langmuir isotherm fit the adsorption data with maximum monolayer adsorption capacity, 151.735 mg/g at 298 K - 168.339 mg/g at 318 K for PBL. The data fitted the pseudo-2nd -order kinetic model for all three adsorbents with a correlation coefficient greater than 0.99, indicating that chemisorption controls adsorption. The Dubinin-Radushkevich isotherm indicated that the mean sorption energy (E) is a physisorption mechanism. So, the process involves physical sorption as well as chemical sorption processes with negligible sorption energy. The FTIR, Raman Spectra, and ¹³C NMR results show that different functional groups of cellulose, hemicellulose and lignin are involved in MG elimination. The theoretical studies were applied for a deeper understanding of the adsorption mechanism of MG using semi-empirical quantum chemical calculations. The DFT Calculations yielded valuable information about quantum chemical properties, like EHOMO, ELUMO, electrophilicity, chemical reactivity, dipole moment, and hardness for adsorbent/adsorbate components and the binding energy from adsorbent/adsorbate interactions. Multiple polynomial regression and genetic algorithm also have been successfully applied to predict the removal percentage of malachite green.
Biosorption has great potential in removing toxic effluents from wastewater, especially heavy metal ions such as cobalt, lead, copper, mercury, cadmium, nickel and other ions. Mathematically modeling of biosorption process is essential for the economical and robust design of equipment employing the bioadsorption process. However, biosorption is a complex physicochemical process involving various transport and equilibrium processes, such as absorption, adsorption, ion exchange and surface and interfacial phenomena. The biosorption process becomes even more complex in cases of multicomponent systems and needs an extensive parametric analysis to develop a mathematical model in order to quantify metal ion recovery and the performance of the process. The biosorption process involves various process parameters, such as concentration, contact time, pH, charge, porosity, pore size, available sites, velocity and coefficients, related to activity, diffusion and dispersion. In this review paper, we describe the fundamental physical and chemical processes involved in the biosorption of heavy metals on various types of commonly employed biosorbents. The most common steady state and dynamic mathematical models to describe biosorption in batch and fixed-bed columns are summarized. Mathematical modeling of dynamic process models results in highly coupled partial differential equations. Approximate methods to study the sensitivity analysis of important parameters are suggested.
Deterioration of water quality is a desperate threat worldwide. Industrial development regularly added a vast amount of organic and inorganic contaminants to water. Therefore, eradicating these contaminants is highly essential for the well-being of biotic components. Adsorption-assisted technologies are among the most benign and principally used due to their higher efficiencies at lower costs and independence of complex technological supports. Carbon nanomaterials, such as activated carbons, carbon nanotubes, graphene-based materials, and carbon dots have been broadly adopted as adsorbents because of their outstanding surface characteristics. Researchers worked a lot on activation procedures and chemicals to achieve an ultrahigh surface area (above 3000 m²/g) to increase the adsorption efficiency. Further, cross-linked carbon nanotubes exhibited much-selected adsorption to organics. Carbon dots, a new type of carbon-based nanomaterials emerged as excellent adsorbents when introduced into the polymers matrix and provided promising platforms for the removal of metal ions. Also, graphene oxide and other oxidized forms of carbon being rich in functional groups are reported to exhibit excellent adsorption capacities as high as 2564 mg/g at 25 °C for basic and cationic compounds.
Here, we reviewed the various types of pollutants found in aquatic biota with some basics on fundamentals and mechanistic features of adsorption, adsorption efficiency regulating factors. The article emphasized the performances of carbon nanomaterials and associated nanocomposites for the adsorption of various pollutants. The review also addresses the essential issues for the technical development and commercial application of carbon-assisted materials as nano adsorbents for water decontamination.
Hexagonal boron nitride (hBN)-magnetite (Fe3O4) nanocomposites (hBN-Fe3O4 NCs) were prepared through in situ coprecipitation via the green route using Callistemon citrinus (CC) and used as adsorbents for the removal of Cr(VI) ions from aqueous solution. The synthesized hBN-Fe3O4 NC was characterized by X-ray diffraction, energy-dispersive X-ray (EDX) spectroscopy and field emission scanning electron microscopy (FE-SEM). The specific surface area was measured using the Brunauer–Emmett–Teller (BET) technique, and magnetic measurements were conducted with a vibrating sample magnetometer (VSM). The functional groups on the surface of hBN-Fe3O4 NC were examined using FTIR spectroscopy. When hBN-Fe3O4 NC was used as an adsorbent for removing Cr(VI) ions from K2Cr2O7 solution, the results showed a very high removal efficiency, almost 100% at low pH. The results showed that removal efficiency decreased with an increase in the pH of the solution. The pseudo-second-order kinetic and Freundlich adsorption isotherm models best fit the data for the adsorption of Cr(VI) on the surface of hBN-Fe3O4 NC. The maximum adsorption capacity was estimated as 208.6 mg/g at 50 °C. Thermodynamic studies showed that the adsorption process was endothermic and spontaneous. Cr(VI) ions adsorbed on the surface of hBN-Fe3O4 NC could be reused at least eight times for adsorptive removal of Cr(VI) with good efficiency. The adsorption mechanism was explored, which indicates that physical adsorption dominates the sorption process, while some contributions from the chemisorption process are also present. A life cycle analysis of the NC production process was also conducted.
A Schiff base modified titania (Sal-TiO2) was synthesized and evaluated for eliminating of radioactive Th (IV) ions in comparison with plain TiO2. Thermodynamic studies exhibited that sorption process is entropy-driven onto studied sorbents. Sal-TiO2 exhibited enhanced adsorption properties, and ΔG° of the Sal-TiO2 was around 36% lower. Investigation of linear forms of Langmuir, Freundlich, and Redlich–Peterson adsorption isotherms demonstrated that the adsorption mechanism was in accordance with the Freundlich model. The kinetics of the adsorption onto adsorbents could be well interpreted by pseudo-second-order model. Kinetic and thermodynamic data have been predicted that physisorption is the most possible mechanism for adsorption.
Ciprofloxacin, a second-generation synthetic fluoroquinolone derivative widely used in human and veterinary medicines, has the potential to pose a serious risk to aquatic organisms and humans. The current research investigated the removal of ciprofloxacin using biochar treated with clay mineral and subsequently activated with carbon dioxide (CO2) produced at two different pyrolysis temperatures (350 and 650 °C). Batch adsorption experiments were carried out to assess the removal efficiency of ciprofloxacin by as-synthesized materials. The effects of various factors, such as pH, contact time, adsorbent dose, initial ciprofloxacin concentration, and temperature were studied during the removal process. The physicochemical characterization results verified the successful loading of clay minerals on biochar. Non-linear adsorption models were employed to understand the nature of adsorption processes however, the Pseudo-second-order kinetic and Freudlich and Redlich Peterson isotherm models best fitted with the adsorption data. These findings indicated that the adsorption did not follow an ideal monolayer adsorption suggesting hybrid chemical adsorption process that was spontaneous and endothermic. The maximum adsorption (50.32 mg g⁻¹) of ciprofloxacin was achieved by CO2 activated biochar-clay mineral composite prepared at 350 °C, and was almost two times higher than the pristine biochar at neutral pH and 40 °C. The possible proposed mechanisms involved for the removal of ciprofloxacin were electrostatic attraction, cation exchange, pore-filling effect, and π-π interactions. Our findings demonstrate that application of CO2 activated biochar-clay mineral composite is a promising technique for efficient removal of ciprofloxacin from aqueous solution.
Various studies have focused on the photocatalytic remediation of toxic organic contaminants in water, but low light utilization and difficult catalyst recovery hindered the prospect of industrial-scale application of photocatalytic technology. The dispersion of photocatalysts into the solution is the major cause of these shortcomings. In this work, an alternative strategy of sequential adsorption followed by photocatalytic degradation was verified. This strategy operated photocatalysis on the solid phase saturated with contaminants, which not only avoided the absorption and barrier of light by water, but also the regenerated catalyst can be directly used for the next cycle. For this, H3PO4-modified TiO2 nanoparticles loaded on biochar (P-TiO2/BC) was used to adsorb dyes and then the collected adsorbent was directly illuminated to degrade the adsorbed dyes. P-TiO2/BC was characterized by XRD, FTIR, XPS, SEM, UV–Vis DRS and N2 adsorption–desorption technologies. The influence of solution pH on the adsorption of P-TiO2/BC, as well as the adsorption kinetics, isotherms and desorption was investigated. Photocatalystic experiments showed that the adsorbed dyes can be completely degraded. The free radical trapping experiments and electron spin resonance were performed to examine the mechanism of dye degradation. In the meantime, the adsorbent regenerated by solid-phase photocatalysis can be reused several times with higher regeneration rates (88.1–69.3%). This work should provide an available approach for the photocatalytic treatment of water pollution and the photo-regeneration of adsorbents.
The interaction mechanism between adsorbent and adsorbate is of great significance in the adsorption process. Activated biochar, prepared from pine sawdust using CO2 and H2O as activator, was employed to adsorb methylene blue in printing and dyeing pollutants. The pore structure, carbon structure of the aromatic ring system, and functional groups were investigated though the characterization analysis, and the adsorption kinetics and possible adsorption mechanism were also studied. The activated biochar prepared by CO2 activation had more specific surface area, pore structure, and surface oxygen‐containing functional groups than that prepared by H2O, which was more conductive to improving its adsorption capacity. The electrostatic interaction between the surface oxygen‐containing functional groups and the π‐π interaction formed in the aromatic rings enhanced the adsorption capacity of activated biochar to methylene blue. The adsorption process of methylene blue by activated biochar was spontaneous, and it conformed to the pseudo‐second‐order kinetic characteristics and Langmuir adsorption isotherm equation. It was a monolayer adsorption and the maximum adsorption capacity was about 160 mg/g. Activated biochar as an adsorbent for wastewater treatment has promising application and development prospects. This article is protected by copyright. All rights reserved.
Activated carbons were prepared from solid cork wastes by physical activation with carbon dioxide or steam, and chemical activation by impregnation with phosphoric acid. In this work we show the possibility of using these activated carbons for the adsorption of phenolic compounds from the aqueous phase. The materials present a different response to the adsorptives used (p-nitrophenol, p-chlorophenol, p-cresol and phenol), depending on the type of activation and the parameters (burn-off, absolute concentration) used in each case. All the samples were capable of retaining the contaminants, with the best result being reached by the sample with higher burn-off and the worst with the carbonised, while intermediate values were reached with the remaining samples. The experimental isotherms were analysed with two and three parameters equations (Freundlich, Langmuir, Dubinin–Radushkevich–Kaganer and Redlich–Peterson). The results obtained from the application of the equations are similar in some aspects, but the degree of confidence is quite different. The best fit was achieved with the Redlich–Peterson equation, which can be explained by the fact that this has three adjustable parameters. However, overall the Freundlich and DRK equations appear to be more useful and provide parameters which can be correlated with the structural characteristics of the solids obtained from N2 adsorption measurements.
Mise au point comportant des definitions generales et la terminologie, la methodologie utilisee, les procedes experimentaux, les interpretations des donnees d'adsorption, les determinations de l'aire superficielle, et les donnees sur la mesoporosite et la microporosite
A carbonaceous sorbent derived from the fruit shell of Indian almond (Terminalia catappa) by sulfuric acid treatment was used for the removal of mercury(II) from aqueous solution. Sorption of mercury depends on the pH of the aqueous solution with maximum uptake occurring in the pH range of 5-6. The kinetics of sorption conformed well to modified second order model among the other kinetic models (pseudo first order and pseudo second order) tested. The Langmuir and Redlich-Peterson isotherm models defined the equilibrium data precisely compared to Freundlich model and the monolayer sorption capacity obtained was 94.43 mg/g. Sorption capacity increased with increase in temperature and the thermodynamic parameters, DeltaH degrees , DeltaS degrees and DeltaG degrees , indicated the Hg(II) sorption to be endothermic and spontaneous with increased randomness at the solid-solution interface. An optimum carbon dose of 4 g/l was required for the maximum uptake of Hg(II) from 30 mg/l and the mathematical relationship developed showed a correlation of 0.94 between experimental and calculated percentage removals for any carbon dose studied. About 60% of Hg(II) adsorbed was recovered from the spent carbon at pH 1.0, while 94% of it was desorbed using 1.0% KI solution.
Carbonaceous adsorbents with controllable pore sizes derived from carbonized pistachio shells (i.e., char) were prepared by the KOH activation and steam activation methods in this work. The pore properties including the BET surface area, pore volume, pore size distribution, and pore diameter of these activated carbons were characterized by the t-plot method based on N2 adsorption isotherms. Through varying the KOH/char ratios from 0.5 to 3, the KOH-activated carbons exhibited BET surface areas ranging from 731 to 1687m2/g with a similar micropore content (80–92%). The carbons activated by steam at 830°C for 2h had a BET surface area of 821m2/g with the micropore content of 42%. The micropore/total pore volume ratio (Vmicro/Vpore) and average pore size (Dpore) were independent of the KOH/char ratio, revealing that KOH activation is a powerful method in developing and controlling the number of micropores with a very similar pore size distribution. The adsorption equilibria and kinetics of methylene blue, basic brown 1, acid blue 74, 2,4-dichlorophenol, 4-chlorophenol, and phenol from water on all activated carbons at 30°C were investigated to demonstrate the fact that adsorption of organics is not only dependent upon the BET surface area but is also determined by the relative size between pores and molecules. The adsorption isotherms were subjected to the model fitting according to Langmuir and Freudlich equations. By comparing the projected area of adsorbates, the surface coverage of phenols is about 3.6 times of that of dyes (based on unit gram of activated carbon). The Elovich equation was found to suitably describe the adsorption process of all KOH-activated carbons while the adsorption behavior on the steam-activated carbon was reasonably fitted with the intraparticle diffusion model.
The sorption of three acid dyes, namely, Acid Red 114, Polar Yellow and Polar Blue RAWL, onto activated carbon, has been studied. Equilibrium isotherms have been measured for three single component systems (AB, AR, AY) and one binary component system (AB+AY). The isotherms were determined by shaking 0.05 g activated carbon, particle size range 500–710 μm, with 0.05 dm3 dye solution of initial concentrations from 10 to 250 mg/dm3. A constant temperature agitating 400-rpm shaking water bath was used and the temperature maintained at 20±2°C. A contact time of 21 days was required to achieve equilibrium. Analysis of data has been carried out in two stages. (a) In single component analysis, the experimental isotherm data were analysed using Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich equations for each individual dye. The monolayer adsorption capacities are 101.0 mg Acid Red per g carbon, 100.9 mg Acid Blue per g carbon and 128.8 mg Acid Yellow per g carbon. (b) In multicomponent analysis, one binary system has been analysed using an extended form of the Langmuir equation. The correlation between theoretical data and experimental data only had limited success due to competitive and interactive effects between the dyes and dye-surface interactions.
Adsorption of reactive dye from aqueous solution onto cross-linked chitosan/oil palm ash composite beads (CC/OPA) was investigated in a batch system. Kinetic and isotherm studies were carried out by considering the effects of various parameters, such as initial concentration (50–500mg/L), contact time, pH (2–13), and temperature (30, 40, 50°C). It was found that the dye uptakes were much higher in acidic solutions than those in neutral and alkaline conditions. Langmuir, Freundlich, Redlich–Peterson, and Temkin isotherms were used to analyze the equilibrium data at different temperatures. The Redlich–Peterson isotherm fits the experimental data significantly better than the other isotherms. Adsorption kinetics data were tested using pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption followed a pseudo-second-order model. The pseudo-first-order and pseudo-second-order rate constants for different initial concentrations were evaluated and discussed. Thermodynamic parameters such as standard Gibbs free energy (ΔG°), standard enthalpy (ΔH°), and standard entropy (ΔS°) were evaluated by applying the Van’t Hoff equation. The thermodynamics of reactive dye adsorption onto cross-linked chitosan/oil palm ash composite beads indicates its spontaneous and endothermic nature.
In the study, bagasse fly ash (BFA) (generated as waste material from sugar mill), was used as an adsorbent for the removal of Orange-G (OG), and Methyl Violet (MV), from aqueous solution. Batch studies were performed to address various experimental parameters like pH, contact time, adsorbent dose and initial concentration for the removal of these dyes. Effective pH for OG and MV removal were 4 and 9, respectively. Greater percentage of dye was removed with decrease in the initial concentration of dyes, and increase in amount of adsorbent used. Kinetic study showed that the adsorption of dyes on BFA was a gradual process. Quasi-equilibrium reached in 4h. Pseudo-first-order, pseudo-second-order, Bangham and intra-particle particle diffusion models were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. Equilibrium isotherms were analysed by Freundlich, Langmuir, Redlich–Peterson, Dubnin–Radushkevich, and Tempkin isotherm equations using correlation coefficients and five different error functions. Freundlich equation is found to best represent the equilibrium data for OG-BFA system while Redlich–Peterson equation better fits the data for MV-BFA system. Thermodynamic study showed that adsorption of MV on BFA (with a more negative Gibbs free energy value) is more favoured among the dyes studied. BFA which was used without any pretreatment showed high surface area, pore volume and pore size exhibiting its potential to be used as an adsorbent for the removal of OG and MV.
Biosorption of chromium using suspended and immobilized cells of Rhizopus arrhizus was studied by evaluating the physicochemical parameters of the solution such as initial chromium ion concentration in both batch and packed bed reactor. The Langmuir, Freundlich and Redlich–Peterson adsorption isotherm models were used in the equilibrium modeling. The Freundlich and Redlich–Peterson adsorption isotherm models were found to fit accurately with the experimental data. Batch experiments demonstrate that the sorption process corresponds to the second-order kinetic model and the kinetics of sorption indicates the process to be diffusion controlled. The diffusivity of chromium in Rhizopus-alginate gel beads was calculated using the shrinking core model, and the diffusivity values were in the ranges of 0.049×10−5 to 0.521×10−5cm2s−1. A good fit was found in the case of controlling intraparticle diffusion for the sorption of chromium. Thomas model, Adams–Bohart and Wolborska models were used to represent the dynamic sorption of chromium using immobilized beads and the model parameters were evaluated using experimental data. The Thomas model represents well the sorption of chromium at different residence times whilst Adams–Bohart model was fitted better at the initial part of the breakthrough. Wolborska model also represents the sorption of chromium accurately.
The adsorption characteristics of hexavalent chromium was studied with an adsorbent developed from waste tamarind hull. Experiments were conducted in batch mode to observe the influence of different parameters such as initial concentration of metal ions, adsorbent dosage, adsorbent particle size, stirrer speed, temperature and pH of the solution. Acidic pH strongly favored the adsorption. With decreasing the pH of the solution from 5.0 to 1.0, the removal of chromium was enhanced from 33% to 99%. The adsorption process was found to follow a pseudo-first-order rate mechanism and the rate constant was evaluated at 30°C. The Freundlich, Redlich–Peterson and the Fritz–Schlunder isotherm fit the equilibrium data satisfactorily. Adsorption of chromium was found to increase with increase in the process temperature. Using an adsorbent dosage of 1.0g/L and an acidic pH (2.0), the equilibrium adsorption capacity of the prepared adsorbent was found to be about 70mg/g at 30°C, which increased to about 81mg/g at 50°C. The entropy change, free energy change and heats of adsorption were determined for the process.
Removal of hydrogen sulfide from aqueous solutions has been studied using cupric oxide (CuO) and zinc oxide (ZnO) as adsorbents. The adsorption capacity of both CuO and ZnO for H2S from aqueous solutions was determined under various conditions of temperature and solution pH. Equilibrium data were used to construct adsorption isotherms and to fit various adsorption models. Results show that increasing temperature leads to an increase in the adsorption capacity of both oxides. Studying the effect of pH at 4, 7 and 11 show that the maximum adsorption capacity of CuO is attained at pH 7. However, the Redlich-Peterson isotherm shows a better fit than both the Langmuir and Fruendlich isotherms.
The micropore volumes of zeolites displaying different external surface areas were determined with the help of two classical methods: the Dubinin–Radushkevich (DR) and t-plot. The results were compared with a new approach, in which adsorption isotherms are decomposed into two adsorption areas: one corresponding to the micropore filling and described by the DR equation, and the other ascribed to adsorption on the external surface and ruled by the classical BET equation. The results indicate that the proposed model fits the experimental data very well. Furthermore, the DR-plot seems to overestimate micropore volume, whereas the t-plot, in the range 6<t<9 Å, underestimates it.
Experimental data of the adsorption of reactive dyestuffs onto Filtrasorb 400 activated carbon (FS400) were determined in an equilibrium isotherm study. As most industrial wastewater contains more than one pollutant, an investigation into the effect of multisolute systems (using the unhydrolysed form of the reactive dyes) on the adsorption capacity was undertaken. Equilibrium isotherm models were employed to describe the adsorption capacities of single, binary and ternary dye solutions. The results of these analyses showed that adsorption of reactive dyes from single and multisolute systems can be successfully described by Langmuir, and Redlich–Peterson equilibrium isotherm models. Experimental data indicated that competitive adsorption for active sites on the carbon surface results in a reduction in the overall uptake capacity of the reactive dyes investigated.
Equilibrium adsorption isotherm for the removal of basic dye (Methylene Blue) from aqueous solution using bituminous coal-based activated carbon has been investigated. Liquid phase adsorption experiments were conducted and the maximum adsorptive capacity was determined. The effect of experimental parameters, namely, pH and adsorbent particle size were studied. Equilibrium data were mathematically modelled using the Langmuir, Freundlich and Redlich–Peterson adsorption models to describe the equilibrium isotherms at different solution pH values and particle sizes, and isotherm constants were determined. The results indicate the potential use of the adsorbent for the removal of Methylene Blue (MB) from aqueous solution. Maximum adsorption capacity of 580 mg/g at equilibrium was achieved. It was found that pH plays a major role in the adsorption process. The optimum pH for the removal of MB from aqueous solution under the experimental conditions used in this work was 11. The Redlich–Peterson isotherm was found to best fit the experimental data over the whole concentration range as indicating from the high values of the correlation coefficients (r2 > 0.99).
The biosorption of Acid Red 337 and Acid Blue 324 from aqueous solution on Enteromorpha prolifera was investigated in a batch system. Optimum initial pH and temperature values for AB 324 and AR 337 dyes were found as 3.0 and 2.0, 25 and 30 °C, respectively and the optimum dye uptake amounts per unit mass were obtained at 0.5 g/l biosorbent concentration for both dyes. The Langmuir, Freundlich and Redlich–Peterson adsorption models were applied to experimental equilibrium data and the isotherm constants were calculated using Polymath 4.1 software. The monolayer covarage capacities of E. prolifera for AB 324 and AR 337 were obtained as 160.6 and 210.9 mg/g, respectively. It was observed that the biosorption data fitted well to Redlich–Peterson model than the other models. The external diffusion and intraparticle diffusion models were also applied to biosorption data of AR 337 and AB 324 and it was found that both the surface adsorption as well as intraparticle diffusion contribute to the actual adsorption process. The constants obtained from the pseudo-second order kinetic model at different temperatures were evaluated and the activation energies for the biosorption of AB 324 and AR 337 were found to be −31.5 and −19.87 kJ/mol, respectively. Thermodynamic parameters such as enthalpy, entropy and Gibb's free energy changes were also calculated and it was concluded that the biosorption of these acidic dyes on E. prolifera was exothermic in nature.
Gemazol Turquise Blue-G, a vinyl sulfone mono-azo type reactive dye, containing copper-phtlalocyanine as cromofor group, was removed from its aqueous solution in batch and continuous packed bed sorption systems by using dried Rhizopus arrhizus as a biosorbent. Operating variables studied were temperature, initial pH, initial dye concentration and sorbent dosage in the batch stirred system and flow rate and inlet dye concentration in the continuous packed bed. In the batch system, the fungal biomass exhibited the highest dye uptake as 773.0 mg g−1 at 45 °C, at an initial pH value of 2.0, at an initial dye concentration of 812.6 mg l−1 for a biomass dosage of 0.5 g l−1. The Freundlich, Langmuir and Redlich–Peterson adsorption models were used for the mathematical description of the biosorption equilibrium and isotherm constants were evaluated at different temperatures. Equilibrium data fitted well the Langmuir model in the studied concentration (100–800 mg l−1) and temperature (25–45 °C) ranges. Sorption data were fitted to pseudo first-order, pseudo second-order and saturation type kinetic models assuming that the external mas transfer limitations in the system can be neglected. The dye uptake process was found to follow pseudo second-order and saturation type kinetics. The thermodynamic parameters calculated showed that the adsorption process is feasible and has an endothermic character. The effect of operating parameters on the sorption characteristics of R. arrhizus in the continuous packed bed was investigated at pH 2.0 and at 25 °C. Data confirmed that the total amount of sorbed dye and column sorption capacity decreased with increasing flow rate and increased with increasing inlet dye concentration. The maximum column biosorption capacity of dried R. arrhizus cells was 823.8 mg g−1 at the highest inlet dye concentration of 776.3 mg l−1 at the minimum flow rate of 0.8 ml min−1. Thomas model was applied to experimental column data to determine the characteristic parameters of column useful for process design and to predict the breakthrough curves. The model was found suitable for describing the whole part of dynamic behavior of the column with respect to flow rate and inlet dye concentration.
Equilibrium studies were carried out at 305 K for the sorption of malachite green onto orange peel for a fixed operating line condition (solution volume/adsorbent mass ratio or V/M ratio). The experimental data were fitted to the Freundlich, Langmuir and Redlich–Peterson isotherms by non-linear method. The best fitting isotherm was found to be the Langmuir and Redlich–Peterson isotherm. Redlich–Peterson is a special case of Langmuir isotherm when the constant g equals unity. A single stage batch adsorber was designed for different operating line (V/M) ratios using the Redlich–Peterson isotherm. Equilibrium data were obtained from the Langmuir isotherm at different V/M ratios using the mass balance equation for the batch adsorber system. A simple linear expression relating the parameters involved in the batch adsorber design was proposed for the studied system.
Adsorption of malachite green (MG) was studied using three adsorbents namely, bagasse fly ash (BFA), a sugar industry waste, and activated carbons commercial grade (ACC) and laboratory grade (ACL). Batch adsorption studies were conducted to evaluate the effect of various parameters such as pH, adsorbent dose, contact time and initial MG concentration on the removal of MG. The initial pH of the dye solution strongly affected the chemistry of both the dye molecules and adsorbents in an aqueous solution. The effective pH was 7.0 for adsorption of MG by the three adsorbents. Equilibrium reached in about 4 h contact time. Optimum BFA, ACC and ACL dosages were found to be 1, 20 and 4 g l−1, respectively. The adsorption followed pseudo-second-order kinetics. Equilibrium adsorption data on BFA, ACC and ACL were analyzed by Freundlich, Langmuir, Dubnin–Radushkevich, Redlich–Peterson and Temkin isotherm equations using regression analysis. Non-linear error analysis showed that the Freundlich isotherm best-fits the equilibrium data for adsorptive removal of MG by BFA and ACC and Redlich–Peterson best follows the equilibrium data for ACL. Thermodynamic study showed that MG adsorption on BFA was comparable to that obtained with ACC or ACL.
The synthetic crystalline hydrous titanium(IV) oxide (CHTO), an anatase variety and thermally stable up to 300 °C, has been used for adsorption of Cr(III) and Cr(VI) from the aqueous solutions, the optimum pH-values of which are 5.0 and 1.5, respectively. The kinetic data correspond very well to the pseudo-second order equation. The rates of adsorption are controlled by the film (boundary layer) diffusion, and increase with increasing temperature. The equilibrium data describe very well the Langmuir, Redlich–Peterson, and Toth isotherms. The monolayer adsorption capacities are high, and increased with increasing temperature. The evaluated ΔG∘ (kJ · mol−1) and ΔH∘ (kJ · mol−1) indicate the spontaneous and endothermic nature of the reactions. The adsorptions occur with increase in entropy (ΔS∘ = positive), and the mean free energy (EDR) values obtained by analysis of equilibrium data with Dubinin–Radushkevick equation indicate the ion-exchange mechanism for Cr(III) and Cr(VI)-adsorptions.
The ability of dried anaerobic activated sludge to adsorb phenol and chromium(VI) ions, both singly and in combination, was investigated in a batch system. The effects of initial pH and single- and dual-component concentrations on the equilibrium uptakes were investigated. The optimum initial biosorption pH for both chromium(VI) ions and phenol was determined as 1.0. Multi-component biosorption studies were also performed at this initial pH value. It was observed that the equilibrium uptakes of phenol and chromium(VI) ions were changed due to the presence of other component. Adsorption isotherms were developed for both single- and dual-component systems at pH 1.0, and expressed by the mono- and multi-component Langmuir, Freundlich and Redlich–Peterson adsorption models and model parameters were estimated by the non-linear regression. It was seen that the mono-component adsorption equilibrium data fitted very well to the non-competitive Freundlich and Redlich–Peterson models for both the components while the modified Freundlich model adequately predicted the multi-component adsorption equilibrium data at moderate ranges of concentration. The results suggested that the cells of dried anaerobic activated sludge bacteria may find promising applications for simultaneous removal and separation of phenol and chromium(VI) ions from aqueous effluents.
Present study deals with the adsorption of phenol on carbon rich bagasse fly ash (BFA) and activated carbon-commercial grade (ACC) and laboratory grade (ACL). BFA is a solid waste obtained from the particulate collection equipment attached to the flue gas line of the bagasse-fired boilers of cane sugar mills. Batch studies were performed to evaluate the influences of various experimental parameters like initial pH (pH0), contact time, adsorbent dose and initial concentration (C0) on the removal of phenol. C0 varied from 75 to 300 mg/l for the adsorption isotherm studies and the effect of temperature on adsorption. Optimum conditions for phenol removal were found to be pH0 ≈ 6.5, adsorbent dose ≈10 g/l of solution and equilibrium time ≈5 h. Adsorption of phenol followed pseudo-second order kinetics with the initial sorption rate for adsorption on ACL being the highest followed by those on BFA and ACC. The effective diffusion coefficient of phenol is of the order of 10−10 m2/s. Equilibrium isotherms for the adsorption of phenol on BFA, ACC and ACL were analysed by Freundlich, Langmuir, Temkin, Redlich–Peterson, Radke–Prausnitz and Toth isotherm models using non-linear regression technique. Redlich–Peterson isotherm was found to best represent the data for phenol adsorption on all the adsorbents. The change in entropy (ΔS°) and heat of adsorption (ΔH°) for phenol adsorption on BFA were estimated as 1.8 MJ/kg K and 0.5 MJ/kg, respectively. The high negative value of change in Gibbs free energy (ΔG°) indicates the feasible and spontaneous adsorption of phenol on BFA. The values of isosteric heat of adsorption varied with the surface loading of phenol.
Many heavy metal-bearing wastewaters also contain their metal cyanide complex ions. Although the biosorption of single or multi-metal ions to various microorganisms has been extensively studied, very little attention has been given to the bioremoval and the expression of the adsorption equilibrium and kinetics of metal–metal cyanide complex ion systems. In this study, the simultaneous biosorption of iron(III) (ferric) cations and iron(III)-cyanide complex (ferricyanide) anions to Rhizopus arrhizus from binary mixtures was studied and compared with single metal and metal cyanide complex ion situation in a batch stirred system. The effects of initial pH and single and dual-component concentrations on the biosorption kinetics and equilibrium uptake of each component, both singly and in mixture were investigated. The working pH value for both species was determined as 2.0. Multi-component biosorption studies were also performed at this pH value. The biosorption rates and equilibrium uptakes of iron(III) or iron(III)-cyanide complex ions increased by the presence of increasing concentrations of the other ion up to 200 mg l−1 for iron(III) and up to 1000 mg l−1 for iron(III)-cyanide complex ions. This situation showed a synergistic interaction between these ions. The Freundlich, Langmuir and Redlich–Peterson adsorption models were used to predict the mono-component equilibrium uptake and model parameters were estimated by the non-linear regression. It was seen that the mono-component adsorption equilibrium data fitted very well to the mono-component Langmuir and Redlich–Peterson models for both the components at moderate ranges of concentration. A modified synergistic Langmuir model was proposed for dual-component system and model parameters were also estimated by the non-linear regression. The pseudo second-order kinetic model was applied to single and multi-component experimental data assuming that the external mass transfer limitations in the system can be neglected and biosorption is sorption controlled.
Equilibrium studies were carried out at 305 K for the sorption of malachite green onto lemon peel. The equilibrium data were fitted to the Freundlich, Langmuir and Redlich-Peterson isotherms by linear and non-linear methods. Non-linear method is a better way to obtain the isotherm parameters. The best fitting isotherm was found to be the Langinuir and Redlich-Peterson isotherm. Redlich Peterson is a special case of Langmuir when the constant g equals unity. (c) 2006 Elsevier Ltd. All rights reserved.
The equilibrium uptake of phenol and nickel(II) ions, both singly and in combination, by dried aerobic activated sludge was studied in a batch system. From the previous studies, the optimum biosorption pH values were determined as 4.5 for nickel(II) and as 1.0 for phenol. Adsorption isotherms were developed for both the single- and dual-component systems at these two pH values and expressed by the mono- and multi-component Langmuir, Freundlich and Redlich–Peterson adsorption models and model parameters were estimated by the non-linear regression method. It was seen that the mono-component adsorption equilibrium data fitted very well to the Redlich–Peterson model for both the components and for both the pH values while all the multi-component adsorption models adequately predicted the multi-component adsorption equilibrium data at moderate ranges of concentration.
The hybrid anilinepropylsilica xerogel (SiAn) was synthesized by sol–gel method and it was used as adsorbent for removing Congo red from aqueous solutions. The dye adsorption experiments were carried out by using bath procedure. The pH effects, the contact time and the initial dye concentration were changed to obtain the best experimental conditions. The dye adsorption equilibrium was rapidly attained after 20 min of contact time. The experimental data were best fitted to Sips and Redlich–Peterson isotherm models, attaining a maximum adsorption capacity of 22.62 mg g−1 of Congo red.
Effects of micropore development through varying the KOH/char ratio on the porous, electrochemical, electronic, and adsorptive properties for corncob-derived activated carbons (ACs) prepared by means of the KOH activation method were systematically compared. The pore properties of ACs, including BET surface area, total pore volume, micropore volume ratio, bulk density, and product yield based on the raw material were investigated to gain an understanding for the influence of KOH dosage on the pore development. Element analysis and temperature-programming desorption (TPD) were used to obtain the information of chemical composition and surface oxygen functional groups on ACs in order to propose the reaction mechanism of KOH activation. Based on the pore development, KOH-activated carbons can be classified into two groups: a combination of physical activation and chemical KOH etching at low KOH/char ratios (0.5–2) as well as chemically uniform etching at high KOH/char ratios (≥3.0). From the adsorption study for five organics with molecular weights varying from 129 to 466 g/mol, the specific adsorption capacity of ACs for organics is independent of their specific surface area. The specific capacitance of ACs reached a maximum as the KOH/char ratio was equal to 3, attributed to a compromise between the specific surface area and electronic resistance of ACs.
Experimentally an identical multimolecular adsorption curve of nitrogen at liquid nitrogen temperature is found for a wide variety of adsorbents, provided no capillary condensation occurs and no narrow pores are put out of action in the course of progressing adsorption. This curve, at present known for relative pressures between 0.10 and 0.75, can be expressed in terms of an average thickness of the adsorbed layer (thet-curve).When experimental adsorption data on microporous adsorbents are plotted as a function of thist-curve, thet-plot obtained gives direct information about the specific area, the capillary condensation, the width of pores, etc.Two equations may describe thet-curve more or less adequately; the theoretical nonsignificance or significance of this is discussed.
The kinetics and thermodynamics of lead ions sorption from aqueous solution on palm kernel fibre have been investigated. The experimental data was analyzed by Langmuir, Freundlich and Redlich–Peterson isotherms using linear coefficient of determination and the non-linear Chi-square test. The equilibrium sorption capacity of lead ions was determined from the Langmuir equation and found to be 49.9 mg/g at 65 °C. A batch sorption model, based on the assumption of the pseudo-second-order mechanism, was applied to predict the rate constant of sorption, the equilibrium sorption capacity and the initial sorption rate with the effect of temperature. An activation energy of sorption was evaluated as 13.5 kJ/mol for the sorption of lead ions on palm kernel fibre. Various thermodynamic parameters, ΔH°, ΔS° and ΔG°, were computed from equilibrium constant values. The results show that the sorption of the lead ions on palm kernel fibre is a spontaneous and endothermic nature process.