Binary Adsorption in a Fixed-Bed Column Packed with an Ion-Exchange Resin

Abstract

A mathematical model was adopted to analyze a binary fixed-bed adsorption column packed with an ion-exchange resin. Two pairs of organic compounds, o-cresol-benzoic acid and p-chlorophenol-p-nitrophenol, were employed as the adsorbates. A modified Langmuir isotherm with interaction factors η _i was found suitable for representing the adsorption equilibrium. Scale-up of the binary adsorption column with respect to column length was effective based on the proposed mathematical model and corresponding methods for estimating the model parameters. The significance of excess concentration in the breakthrough curve was related to inlet concentration, column length, and the difference in adsorption affinity.     

Removal of Cr(VI) From Aqueous Solution by Turkish Vermiculite: Equilibrium,Thermodynamic and Kinetic Studies

Abstract

The adsorption of Cr(VI) from aqueous solution by Turkish vermiculite were investigated in terms of equilibrium, kinetics, and thermodynamics. Experimental parameters affecting the removal process such as pH of solution, adsorbent dosage, contact time, and temperature were studied. Equilibrium adsorption data were evaluated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir model fitted the equilibrium data better than the Freundlich model. The monolayer adsorption capacity of Turkish vermiculite for Cr(VI) was found to be 87.7 mg/g at pH 1.5, 10 g/L adsorbent dosage and 20°C. The mean free energy of adsorption (5.9 kJ/mol) obtained from the D–R isotherm indicated that the type of sorption was essentially physical. The calculated thermodynamic parameters (ΔG ^o , ΔH ^o and ΔS ^o ) showed that the removal of Cr(VI) ions from aqueous solution by the vermiculite was feasible, spontaneous and exothermic at 20–50°C. Equilibrium data were also tested using the adsorption kinetic models and the results showed that the adsorption processes of Cr(VI) onto Turkish vermiculite followed well pseudo-second order kinetics.     

Preparation, Characterization and Adsorption Performance of Cetyl Pyridine Bromide Modified Bentonites

Benzoic acid removal is important for the water treatment and adsorption is an effective treatment process. Cetyl pyridine bromide-modified bentonites (CPB-Bent) and hydroxy-aluminum-pillared bentonites (Al(OH)-Bent) were prepared and characterized by XRD, FTIR and BET. Adsorption experiments were conducted on the adsorption of benzoic acid onto natural bentonites, sodium bentonites (Na-Bent), Al(OH)-Bent and CPB-Bent in batch experiments. Benzoic acid removal onto CPB-Bent is pH dependent and the optimum adsorption is observed at pH ~3.5. The adsorption rate was fast and equilibrium was established within 90-min. The adsorption rate of benzoic acid on CPB-Bent fit a pseudo-second order kinetics model well (R ² = 0.999). The results were analyzed according to the Henry, Langmuir, Freundlich, and Dubinin-Radushkevich isotherm model equations. The adsorption data is well interpreted by the Langmuir isotherm model. Benzoic acid solution at a concentration of 0.5 mmol/L was adsorbed by CPB-Bent; and, the final adsorption efficiency was greater than 90%. The results show that benzoic acid adsorption capability of CPB-Bent is high with the maximum adsorption capability of 94.34 mg/g, which suggests that CPB-Bent is an excellent adsorbent for effective benzoic acid removal from water.     

Evaluating isotherm models for the prediction of flue gas adsorption equilibrium and dynamics

We evaluated isotherm models for the precise prediction of adsorption equilibrium and breakthrough dynamics. Adsorption experiments were performed using pure N₂, CO₂ and their binary mixture with an activated carbon (AC) material as an adsorbent. Both BET and breakthrough measurements were conducted at various conditions of temperature and pressure. The corresponding uptake amount of pure component adsorption was experimentally determined, and parameters of the four different isotherm models, Langmuir, Langmuir-Freundlich, Sips, and Toth, were calculated from the experimental data. The predictive capability of each isotherm model was also evaluated with the binary experimental results of binary N₂/CO₂ mixtures, by means of sum of square errors (SSE). As a result, the Toth model was the most precise isotherm model in describing CO₂ adsorption equilibrium on the AC. Based on the breakthrough experimental result from the binary mixture adsorption, non-isothermal modeling for the adsorption bed was performed. The breakthrough results with all of the isotherm models were examined by rigorous dynamic simulations, and the Toth model was also the most accurate model for describing the dynamics.     

Single and competitive isotherms of phenol ando-cresol by pulsed-input method

There is a considerable industrial interest in both the scale-up and optimization of chromatographic operations used in the purification of fine chemicals and biomolecules. One of the major factors affecting the adsorption operation is the adsorption isotherm. Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to measure the adsorption isotherm of phenol ando-cresol. From the experimental results, the retention times were decreased with increasing sample sizes, and the front of the peak was very stiff, so Langmuir adsorption isotherm was applied. Also Early-eluting component, phenol, in a mixture of the two components elutes faster than that in a pure component. Pulsed-injection method (PIM) was used to determine the two parameters of the Langmuir isotherm. The resulting parameters, a and b, were used to calculate the elution profiles of phenol ando-cresol in pure and mixed state. The agreement between the experimental data and calculated elution profiles was fairly good in a mixture as well as a pure component.     

Removal of Basic Blue 3 by sorption onto a weak acid acrylic resin

A weak acid acrylic resin was used as an adsorbent for the investigation of Basic Blue 3 (BB3) adsorption kinetics, isotherms, and thermodynamic parameters. Batch adsorption studies were carried out to evaluate the effect of pH, contact time, initial concentration (28–100 mg/g), adsorbent dose (0.05–0.3 g), and temperature (290–323 K) on the removal of BB3. The adsorption equilibrium data were analyzed by the Langmuir, Temkin, and Freundlich isotherm models, with the best fitting being the first one. The adsorption capacity (Q_o) increased with increasing initial dye concentration, adsorbent dose, and temperature; the highest maximum Q_o (59.53 mg/g) was obtained at 323 K. Pseudo‐first‐order and pseudo‐second‐order kinetic models and intraparticle diffusion models were used to analyze the kinetic data; good agreement between the experimental and calculated amounts of dye adsorbed at equilibrium were obtained for the pseudo‐second‐order kinetic models for the entire investigated concentrations domain. Various thermodynamic parameters, such as standard enthalpy of adsorption (ΔH^o = 88.817 kJ/mol), standard entropy of adsorption (ΔS^o = 0.307 kJ mol^?1 K^?1), and Gibbs free energy (ΔG^o < 0, for all temperatures investigated), were evaluated and revealed that the adsorption process was endothermic and favorable. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Simulation of CO2/CH4 high pressure separation on microporous activated carbon

Abstract

Pure component adsorption equilibrium of CH₄ and CO₂ on activated carbon have been studied at three different temperatures, 298, 323, and 348?K within a pressure range of 10–2000?kPa. Binary adsorption equilibrium isotherm was described using extended Sips equation and ideal adsorbed solution theory (IAST) model. Experimental breakthrough curves of CO₂/CH₄ (40:60 in a molar basis) were performed at four different pressures (300, 600, 1200, and 1800?kPa). The experimental results of binary isotherms and breakthrough curves have been compared to the predicted simulation data in order to evaluate the best isotherm model for this scenario. The IAST and Sips models described significantly different results for each adsorbed component when higher pressures are set. These different results cause a significant discrepancy in the estimation of the equilibrium selectivity. Simulated and experimental equilibrium selectivity data provided by IAST presented values of around 4, for CO₂/CH₄, and extended Sips presented values of around 2. Also, simulated breakthrough curves showed that IAST fits better to the experimental data at higher pressures. According to the simulations, in a binary mixture at total pressure over 800?kPa, extended Sips model underestimated significantly the CO₂ adsorbed amount and overestimated the CH₄ adsorbed amount.     

Modeling of the Temperature Variation Effects on the Polymerization Reactions of Phenolics on Granular Activated Carbon

Abstract

The effect of temperature variation on the kinetics of adsorption and adsorption-reaction combination of phenol and o-cresol on granular activated carbon (GAC) was evaluated throughout this study. Batch experiments were performed under oxic and anoxic conditions at temperatures of 8, 21, and 35°C. The results showed that the equilibration time for physical adsorption increased with the decrease in temperature and occurred in the time range of 7.5–11 days for the adsorption-reaction combination (oxic cases). The polymerization reactions lagged by about 10 hours under all of the temperature values. Diffusivity coefficients in the anoxic cases increased proportionally with temperature, with the highest difference between oxic and anoxic diffusivities at a temperature 35°C. The homogeneous surface diffusion model (HSDM) accurately predicted the anoxic batches and deviated from the oxic data. Temperature increases the adsorption and polymerization reaction rates, and thus the predictivity of the HSDM for both oxic and anoxic batches improves. Under controlled dissolved oxygen (DO) and temperature conditions, the isotherm and batch equilibrium capacities matched with a maximum deviation of 4%. The effect of temperature on the rate of the DO-induced enhancement was found to follow a self-retardant reaction model. The developed model showed strong predictive capability for the temporal formation of polymers.     

EFFECT OF TEMPERATURE ON THE ADSORPTION OF METHYLENE BLUE DYE ONTO SULFURIC ACID–TREATED ORANGE PEEL

The present study explains the preparation and application of sulfuric acid–treated orange peel (STOP) as a new low-cost adsorbent in the removal of methylene blue (MB) dye from its aqueous solution. The effects of temperature on the operating parameters such as solution pH, adsorbent dose, initial MB dye concentration, and contact time were investigated for the removal of MB dye using STOP. The maximum adsorption of MB dye onto STOP took place in the following experimental conditions: pH of 8.0, adsorbent dose of 0.4 g, contact time of 45 min, and temperature of 30°C. The adsorption equilibrium data were tested by applying both the Langmuir and Freundlich isotherm models. It is observed that the Freundlich isotherm model fitted better than the Langmuir isotherm model, indicating multilayer adsorption, at all studied temperatures. The adsorption kinetic results showed that the pseudo-second-order model was more suitable to explain the adsorption of MB dye onto STOP. The adsorption mechanism results showed that the adsorption process was controlled by both the internal and external diffusion of MB dye molecules. The values of free energy change (ΔG ^o) and enthalpy change (ΔH ^o) indicated the spontaneous, feasible, and exothermic nature of the adsorption process. The maximum monolayer adsorption capacity of STOP was also compared with other low-cost adsorbents, and it was found that STOP was a better adsorbent for MB dye removal.     

Propane/Propylene Separation by Simulated Moving Bed II. Measurement and Prediction of Binary Adsorption Equilibria of Propane,Propylene, Isobutane,and 1-Butene on 13X Zeolite

Abstract

The design of a simulated moving bed (SMB) process relies on valid thermodynamic predictions of multicomponent adsorption built up from accurate binary adsorption equilibrium data. Experimental adsorption equilibria of binary mixtures constituted by propane, propylene, isobutane and 1-butene on 13X zeolite were determined using breakthrough experiments at 373 K and 150 kPa. In addition, these binary adsorption experiments allow to confirm the choice of isobutane as an interesting desorbent for the separation of propane-propylene by SMB, since it has an intermediate selectivity between the two species to separate. Various prediction models are available in the literature but only a few of them have both physical and thermodynamical consistency. The ideal adsorbed solution theory (IAST), the thermodynamically consistent extended Toth model (TCET), and the physically-consistent extended Toth isotherm (PCET) were used to predict binary adsorption equilibria from pure component adsorption isotherms parameters. The PCET model was found suitable for representing the adsorption equilibrium of the different hydrocarbon mixtures with a reasonably good accuracy.     

Removal of Copper (II) and Nickel (II) Ions from Aqueous Solutions by a Composite Chitosan Biosorbent

Abstract

A composite chitosan biosorbent (CCB) was prepared by coating chitosan on to ceramic alumina. The adsorption characteristics of the sorbent for copper and nickel ions were studied under batch equilibrium and dynamic flow conditions at pH 4.0. The equilibrium adsorption data were correlated with Langmuir, Freundlich, and Redlich‐Peterson models. The ultimate monolayer capacities, obtained from Langmuir isotherm, were 86.2 and 78.1 mg/g of chitosan for Cu(II) and Ni(II), respectively. In addition, dynamic column adsorption studies were conducted to obtain breakthrough curves. After the column was saturated with metal ions, it was regenerated with 0.1 M sodium hydroxide. The regenerated column was used for a second adsorption cycle.     

Removal of Carbon Dioxide from Light Gas Mixtures using a Porous Strontium(II) Silicoaluminophosphate Fixed Bed: Closed Volume and Portable Applications

A Sr²⁺ -SAPO-34 bed was assembled to study CO₂ dynamic adsorption under conditions that emulate those found in closed volume and portable applications. Although the surface area was reduced by 7% during pelletization, adsorption capacities estimated from breakthrough curves compared well with static volumetric adsorption data. Modeling of the breakthrough adsorption was achieved using a Linear Driving Force mass transfer rate model, showing good agreement with the experimental data and confirming fast kinetics and efficient use of the bed. Fast kinetics were also evidenced by the length of the unused section of the bed as calculated from a Mass Transfer Zone model. Adsorption capacity degradation was not observed after multiple regeneration cycles. Apparent and equilibrium adsorption isotherm data estimated from the bed and static volumetric experiments at 25° C were compared to that of 5A Zeolite. These showed that Sr²⁺ -SAPO-34 is a superior adsorbent for CO₂ removal in the low partial pressure range (<1500 ppm). CO₂ and H₂ O multicomponent adsorption breakthrough curves were also gathered for a CO₂ inlet concentration of 1000 ppm and dew points of ?5 and 8° C. The addition of moisture resulted in a decrease in total processed gas volume by 31 and 47%, respectively.     

Pecan Nutshell as Biosorbent to Remove Toxic Metals from Aqueous Solution

Abstract

In the present study we reported for the first time, the feasibility of pecan nutshell (PNS-Carya illinoensis) as an alternative biosorbent to remove Cr(III), Fe(III) and Zn(II) metallic ions from aqueous solutions. The ability of PNS to remove these metallic ions was investigated by using batch biosorption procedure. The effects, such as pH and the biosorbent dosage on the adsorption capacities of PNS were studied. Five kinetic models were tested, the adsorption kinetics being the better fitted one to the fractionary-order kinetic model.

The equilibrium data were fitted to Langmuir, Freundlich, Sips, and Redlich-Peterson isotherm models. Taking into account a statistical error function, the data were best fitted to Sips isotherm models. The maximum biosorption capacity of PNS were 93.01, 76.59, and 107.9 mg g^?1 for Cr(III), Fe(III), and Zn(II), respectively.     

Unusual adsorber dynamics due to S-shaped equilibrium isotherm

A fixed bed adsorption study has been performed to investigate the effect of S-shaped (Type V) equilibrium isotherm on the breakthrough patterns. The adsorption breakthrough data of benzene vapours on dealuminated zeolite Y were collected by using a lab-scale fixed bed apparatus. It was found that the adsorption system, at influent concentrations from 100 to 5,000 ppm at 303 K, yields breakthrough curves of unusual shapes. A mathematical model was applied to predict the complex breakthrough patterns at various conditions. The experimental and modelling results suggest that the unusual breakthrough curve is due to the basic shape of the equilibrium isotherm.     

Experimental study and modelling of an azo colourant dynamic adsorption onto functional cross-linked chitosan/ceramic particles in a fixed bed column

The use of azo dyes in industrial activities generates a large volume of contaminated wastewater; these pollutants in water bodies affect aquatic biota and human health. A functional biocomposite sorbent material was synthesized using cross-linked chitosan with oxalic acid that forms a coating on alumina ceramic particles (AOCh). The removal of Reactive Red 195, a reactive azo dye, using a fixed-bed adsorption column filled with this material was tested. AOCh was physico-chemically characterized by Fourier transform infrared spectroscopy–total attenuated reflection (FTIR-ATR), scanning electron microscopy–energy dispersion spectrometry X-ray (SEM-EDS), X-ray diffraction (XDR), thermo-gravimetric analysis (TGA), and Z-potential. The dynamic adsorption performance was analyzed from experimental breakthrough curves obtained in fixed-bed columns by modifying different operating conditions (bed depth, volumetric flow rate, and dye inlet concentration). Equilibrium adsorption isotherms were determined under dynamic conditions and compared with batch results. The maximum adsorption capacity of the dynamic equilibrium isotherm obtained from the continuous assays was 331 mg/g; this value was the highest in comparison to other tested materials reported in the literature. Different dynamic adsorption models were applied to fit experimental data, including Thomas, Bohart–Admas, Yoon–Nelson, logistic general model, bed depth surface time (BDST), and modified dose response (Yan) models. A critical analysis of these equations was presented, showing the equivalences and the relationship among the coefficients. The Yan model achieved the highest level of agreement between the experimental and predicted values of the breakthrough curves. The use of this model enables scaling-up the industrial process for dye removal. The present work proposed a novel biosorbent material and contributes to the analysis of industrial dye removal under dynamic conditions.     

Kinetic and Equilibrium Studies on the Adsorption of Crystal Violet Dye using Kaolin as an Adsorbent

Abstract

Experimental investigations are carried out to adsorb toxic crystal violet dye from aqueous medium using kaolin as an adsorbent. Characterization of kaolin is done by measuring

1. particle size distribution using particle size analyzer,

2. BET surface area using BET surface analyzer,

3. structural analysis using X ray diffractometer, and

4. microscopic analysis using scanning electron microscope.

The effects of initial dye concentration, contact time, kaolin dose, stirring speed, pH, and temperature are studied for the adsorption of crystal violet in batch mode. Adsorption experiments indicate that the extent of adsorption is strongly dependent on the pH of the solution. Free energy of adsorption (ΔG ^o ), enthalpy (ΔH ^o ), and entropy (ΔS ^o ) changes are calculated to know the nature of adsorption. The calculated values of ΔG ^o are ?4.11 and ?4.48 kJ/mol at 295 K and 323 K, respectively, for 20 mg/L of dye concentration, which indicates that the adsorption process is spontaneous. The estimated values of ΔH ^o and ΔS ^o show the negative and positive sign, respectively, which indicate that the adsorption process is exothermic and the dye molecules are organized on the kaolin surface in more random fashion than in solution. The adsorption kinetic has been described by pseudo first order, pseudo second order and intra‐particle diffusion models. It is observed that the rate of dye adsorption follows pseudo second order model for the dye concentration range studied in the present case. Standard adsorption isotherms are used to fit the experimental equilibrium data. It is found that the adsorption of crystal violet on kaolin follows the Langmuir adsorption isotherm.     

Adsorption of Cresols on Zinc-Aluminium Hydroxides – A Comparison with Zeolite-X

Liquid phase adsorption of m-cresol on Zn-Al hydroxide adsorbents with three different Zn/Al molar ratios was studied in different solvents and compared with commercial zeolite 13X. Among the three adsorbents, ZA-16 showed adsorption capacity similar to commercial zeolite 13X. Solvents used for the preparation of m-cresol solution were found to influence the adsorption capacity. The adsorption capacity was maximum for the solution of m-cresol in n-hexane. Conventional Langmuir and Freundlich adsorption isotherm equations were used to explain the adsorption behavior. The kinetics of m-cresol adsorption followed the first-order Lagergren kinetic model. p-Cresol/m-cresol separation factor was the highest when toluene was used as the organic medium.     

Adsorption of cationic dye from aqueous solutions by activated carbon

Batch sorption experiments were carried out to remove a cationic dye, methylene blue (MB), from its aqueous solutions using a commercial activated carbon as an adsorbent. Operating variables studied were pH, stirring speed, initial methylene blue concentration and temperature. Adsorption process was attained to the equilibrium within 5 min. The adsorbed amount MB dye on activated carbon slightly changed with increasing pH, and temperature, indicating an endothermic process. The adsorption capacity of methylene blue did not significantly change with increasing stirring speed. The experimental data were analyzed by various isotherm models, and found that the isotherm data were reasonably well correlated by Langmuir isotherm. Adsorption measurements showed that the process was very fast and physical in nature. Thermodynamic parameters such as the adsorption entropy (ΔS^o) and adsorption enthalpy (ΔH^o) were also calculated as 0.165 kJ mol⁻¹ K⁻¹ and 49.195 kJ mol⁻¹, respectively. The ΔG^o values varied in range with the mean values showing a gradual increase from −0.256 to −0.780 to −2.764 and −7.914 kJ mol⁻¹ for 293, 313, 323 and 333 K, respectively, in accordance with the positive adsorption entropy value of the adsorption process.     

EQUILIBRIUM,KINETICS, AND BREAKTHROUGH STUDIES FOR ADSORPTION OF Cr(VI) ON CHITOSAN

Wastewater containing low levels of pollutants can be effectively treated by the adsorption technique. In the present work, an adsorption study was carried out using chitosan as adsorbent in a fixed-bed column for the removal of Cr(VI) from wastewater solutions. The column performance of Cr(VI) adsorption onto chitosan was studied at different bed heights (3–9 cm), flow rates (50–200 mL/min), initial metal concentrations (2–10 mg/L), pH values (2–7), and temperatures (30°–60°C). The equilibrium data for the batch adsorption of Cr(VI) on chitosan were tested using the Langmuir, Freundlich, and BET isotherm models. The Langmuir model was found to be the most suitable, with a maximum adsorption capacity of 35.7 mg/g and a correlation coefficient (R ²) = 0.952. The experimental data were found to fit well with the pseudo-second-order kinetic model, with R ² = 0.999. The dynamics of the adsorption process was modeled using the Adams-Bohart, Thomas, and mass transfer models. The models were used to predict the breakthrough curves of adsorption systems and to determine the characteristic design parameters of the column. The adsorption data were observed to fit well with all three models. The model parameters were derived using MATLAB software. In order to compare quantitatively the applicability of adsorption dynamic models in fitting to experimental data, the percentage relative deviation (P) was calculated and found to be less than 5, confirming that the fit is good for all three models.