Optimal process parameters for fixed bed adsorption

For maximum dynamic adsorptive capacity per unit cost, this study shows optimal breakthrough level, flow velocity, bed length, and adsorbent size for a typical case of aqueous adsorbates through a granular carbon bed, regardless of adsorption mechanism and isotherm. While computed optimal adsorbent sizes are smaller than common ones, other optimal parameter values fall within their respective normal ranges.     

Fixed bed column adsorption of ACID Yellow 17 dye onto Tamarind Seed Powder

The intention of this study was to explore the efficacy and feasibility for Acid Yellow 17 adsorption onto fixed bed column of Tamarind Seed Powder. The effect of various parameters like flow rate, initial concentration of dye, bed height, and pH were exploited in this study. The Thomas, Yoon–Nelson, Bed Depth Service Time (BDST), and Adams and Bohart model were analysed to evaluate the column adsorption performance. The adsorption capacity, rate constant and correlation coefficient associated to each model for column adsorption was calculated and mentioned. The adsorption capacity increases with increasing initial dye concentration and bed height and decreasing flow rate. The maximum adsorption capacity related to Adams and Bohart model was found to be 978.5 mg/g at initial concentration of 50 ppm at constant flow rate of 15 mL/min, bed height of 15 cm, and pH 7. Le but de cette étude était d'explorer l'efficacité et la faisabilité de l'Acid Yellow 17 adsorption sur colonne à lit fixe de Tamarind Seed Powder. L'effet de différents paramètres comme le débit, la concentration initiale de colorant, la hauteur du lit et le pH ont été exploitées dans cette étude. Le Thomas, Yoon‐Nelson, BDST et Adams et le modèle Bohart ont été analysées pour évaluer les performances d'adsorption colonne. La capacité d'adsorption, constante de vitesse et coefficient de corrélation associé à chaque modèle de la colonne d'adsorption a été calculé et mentionné. Les augmentations de capacité d'adsorption avec une concentration croissante de colorant initial et un lit en hauteur et le débit diminue. La capacité maximale d'adsorption liées au modèle Adams et Bohart a été trouvé à 978,5 mg/g à la concentration initiale de 50 ppm à débit constant de 15 ml/min, la hauteur du lit de 15 cm et un pH de 7.     

Continuous fixed bed biosorption of Cu2+ ions: application of a simple two parameter mathematical model

Biomass from two fungi of the Mucorales order, laboratory cultured and immobilised Rhizopus arrhizus, and industrial waste Mucor miehei, was tested for capacity to adsorb copper from solution in batch and continuous‐flow column systems. Maximum uptake levels were c 400 and 300 mmol g⁻¹ (dry weight) respectively. Immobilisation of Rhizopus arrhizus in polyvinyl formal to cell loadings of 60% (w/w) did not diminish metal uptake levels. In continuous‐flow columns both biosorbents adsorbed copper to levels equal or approaching the batch uptake values. Column breakthrough curves were fitted to a two parameter model and each of the parameters, σ and t₀ , were linearly correlated with column operating parameters. Predicted breakthrough curves agreed closely with experimental values. © 1999 Society of Chemical Industry     

Sequential experimental design for estimation and analysis of thermal parameters in a fixed bed

The analysis of the effective radial thermal conductivity and the film heat transfer coefficient were carried out in a fixed bed. The temperature profiles were described by two‐dimensional pseudo‐homogeneous model. The thermal parameters were estimated using a sequential experimental design technique. The minimum volume criterion was used to design the next point for temperature measurement in the bed. The utilization of T = T₀ (constant) as the boundary condition at the bed inlet resulted in an axial variation of thermal parameters, which was the factor responsible for the inadequacy of the model in fitting experimental data of different bed heights simultaneously. Using T = T(r) as the boundary condition makes the thermal parameters independent of the axial position and the model statiscally adequate to describe the axial and radial temperature profiles throughout the bed.     

Removal characteristics of some priority organic pollutants from water in a fixed bed fly ash column

The efficiency of a coal fly ash (generated from a thermal power plant) adsorption column for the removal of some priority organic pollutants, viz phenol, o‐hydroxyphenol, m‐hydroxyphenol and 4‐nitrophenol from aqueous solution has been studied. The column performance was evaluated from the concept of the formation of a primary adsorption zone and the breakthrough curve. The extent of solute removal obtained from breakthrough curve during column operation was compared with that obtained from the isotherm parameters for batch operation. The loaded solutes in the column were successfully eluted with acetone, achieving 98% recovery. In order to determine the practical applicability of the column operation the process was repeated a number of times and the variation of column capacity with number of operation cycles was evaluated. Even after six successive cycles, the column was found to retain almost 80% capacity. Copyright © 2005 Society of Chemical Industry     

Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed‐bed column experiments

This paper evaluates the potential use of a locally available organic soil amendment as a low‐cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed‐bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo‐second‐order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow‐rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate‐controlled pore diffusion was successfully performed. The adsorption process was reversed, regenerating the columns by eluting the cadmium using 0.1 mol dm^?3 hydrochloric acid. The high retention capacity together with the favourable structural characteristics indicated that this material could be used as an effective and low‐cost adsorbent for treatment of wastewaters containing heavy metals. Copyright © 2006 Society of Chemical Industry     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

Determination of adsorption operating conditions in dynamic mode on basis of batch study: Application for Dimethylphthalate elimination on activated carbon prepared from Arundo donax

This study aims to determine the operating conditions to implement the Dimethylphthalate removal using an activated carbon prepared from Arundo donax, carbonized at 358?°C during 13?min. To achieve this objective, the study is conducted in batch and dynamic mode. Several kinetic models are applied, namely pseudo-first order, pseudo-second order, intragranular, and Bangham models. The pseudo-second-order model fits the data perfectly, the estimated regression coefficients >0.999. The intragranular diffusion takes place in two stages. The two-parameter (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and three-parameter models (Redlich-Peterson, Sips, and Toth) are applied to model the equilibrium isotherms. The nonlinear regression methodology based on the error functions (hybrid fractional error function, Marquardt’s percent standard deviation, average relative error, Sum of the absolute errors) is applied. The HYBRID fits properly the data showing that the Temkin model gives the best fitting (R²_adj = 0.992), and the Dubinin-Radushkevich model the worst (R²_adj = 0.793). The thermodynamic study shows that the adsorption occurs according to a physical process. The DMP desorption is more effective with a 5% NaOH solution. In dynamic mode, the runs are conducted in fixed bed column. The effect of the bed height, the DMP initial concentration, and the flow rate on the breakthrough curves is investigated, then these breakthrough curves are modeled using the Thomas and Bed Depth Service Time models. The regeneration of the exhausted Arundo donax activated carbon is performed in a column, after 5 cycles, the breakthrough time decreases from 65.3?to 26.8?h, however, the exhaustion time varies less rapidly.     

Experimental,equilibrium modelling,and column design for the reactive separation of biomass-derived 2-furoic acid

Electrochemical conversion of biomass to value-added chemicals has gained impetus in recent years. Herein, we present a methodology for recovering biomass-derived 2-furoic acid from the dilute aqueous stream by reactive extraction. The reactive extraction was performed using a chemical extractant, trioctylamine (TOA), with diluents (octanol, chloroform, and diethyl ether). Equilibrium parameters influencing the recovery of 2-furoic acid were evaluated. Using TOA in various diluents, the 2-furoic acid was recovered with 85%–99% efficiency. A 1:1 complex of the 2-furoic acid—TOA was formed in the organic phase, and the experimental equilibrium complexation constant was compared with that obtained from the relative basicity and Langmuir models. The equilibrium parameters were used for column design to estimate the solvent to feed ratio (S/F) and the number of theoretical stages (NTS). The NTS required is 12 to attain 99% recovery of 2-furoic acid in counter-current extraction. The present study sheds light on the reactive extraction process adopted for process intensification with electrochemical conversion, paving the way for the commercialization of valuable products obtained from biomass.     

Analytic expressions for the isosteric heat of adsorption from adsorption isotherm models and two-dimensional SAFT-VR equation of state

The isosteric heat of adsorption is an important thermodynamic property used to characterize and optimize adsorption processes. In this work, analytic expressions for isosteric heats of adsorption are derived for a collection of commonly used isotherm models and a two-dimensional molecular equation of state based on the SAFT-VR approach. The use of these expressions is presented with an example of adsorption of nitrous oxide, N₂O, on biochar, which is a waste biomass charcoal that exhibits high adsorption potential. The results show that accurate fitting of the adsorption isotherms leads to consistent results obtained with different approaches; however, the predicted isosteric heat of adsorption exhibits strong variations in the regions where experimental data is insufficient such in the region of low pressure/low coverage. Convergence on the prediction of the isosteric heat of adsorption by the different models is only observed in the region where no extrapolation of experimental data is needed.     

Preparation and adsorption properties of chitosan–poly(acrylic acid) nanoparticles for the removal of nickel ions

Chitosan (CS) nanoparticles with different mean sizes ranging from 100 to 195 nm were prepared by ionic gelation of CS and poly(acrylic acid) (PAA). Variations in the final solution pH value and CS : PAA volume ratio were examined systematically for their effects on nanoparticle size, intensity of surface charge, and tendency toward particle aggregation. The sorption capacity and sorption isotherms of the CS–PAA nanoparticles for nickel ions were evaluated. The parameters for the adsorption of nickel ions by the CS–PAA nanoparticles were also investigated. The CS–PAA nanoparticles could sorb nickel ions effectively. The sorption rate for nickel ions was affected significantly by the initial concentration of the solution, sorbent amount, particle size, and pH value of the solution. The samples of nanoparticles were well correlated with Langmuir's isotherm model, and the adsorption kinetics of nickel correlated well with the pseudo‐second‐order model. The maximum capacity for nickel sorption deduced from the use of the Langmuir isotherm equation was 435 mg/g, which was significantly higher than that of the micrometer‐sized CS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Large‐scale isolation and purification of C‐phycocyanin from the cyanobacteria Anabaena marina using expanded bed adsorption chromatography

BACKGROUND: Phycobiliproteins are water soluble proteins useful as fluorescent markers of cells and macromolecules, and as natural colorants, and are anticarcinogenic. Although phycobiliproteins have many applications, their use is limited by the high cost of the purified macromolecules, mainly related with the cost of extraction and purification. In this study a fast and scalable method for preparative extraction and purification of C‐phycocyanin (C‐PC) from Anabaena marina is developed. RESULTS: The method developed consists in the extraction of phycobiliproteins using repeated single contact strategy, separation being performed by expanded bed adsorption (EBA) chromatography using Streamline‐DEAE. Optimal conditions for EBA were obtained at small scale, using a 15 mm internal diameter column, these being a sample load of 0.9 mg C‐PC mL^?1 adsorbent, an expanded bed volume twice the settled bed volume and a sample viscosity of 1.109 mP. The process was then scaled up 36 times, the success of the scale‐up process being verified. Finally, to obtain pure C‐PC conventional ion‐exchange chromatography was utilized. CONCLUSION: Small diameter columns was shown to be useful to simulate the behavior of larger diameter columns for use in scaled up systems. Expanded bed adsorption was demonstrated to be a scalable technology allowing large quantities of C‐PC to be obtained, maintaining high protein recovery while reducing both processing cost and time. The proposed methodology allows recovery of more than 62% of the C‐PC contained in the biomass in the form of pure C‐PC concentrates. Copyright © 2010 Society of Chemical Industry     

Bamboo charcoal modified with Cu2+ and 3-aminopropyl trimethoxy silane for the adsorption of acid fuchsin dye: Optimization by response surface methodology and the adsorption mechanism

The bamboo charcoal modified with Cu²⁺ and 3-aminopropyl trimethoxy silane (BC-Cu/Si-NH₂) was synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and surface acid–base potentiometric titration. The adsorption for acid fuchsin (AF) dyes onto BC-Cu/Si-NH₂ was investigated. Moreover, response surface methodology was performed to optimize the process parameters including pH, initial dye concentration, adsorbent dosage, and temperature. The results presented that the adsorption process was mainly influenced by initial AF concentration and adsorbent dosage. Isotherm studies revealed that the adsorption data fitted well with the Sips model and Dubinin–Radushkevich (D–R) model, which indicated the monolayer, homogeneous, and physical nature of the adsorption process. The maximum adsorption capacity calculated from D–R model could approach approximately to 14.91 mg g⁻¹ at 40 °C, and the maximum adsorption capacity of Sips reached to 10.77 mg g⁻¹ at 40 °C. The kinetic experimental data matched well with Spahn and Schlunder model as well as pseudo-second-order model. In addition, intraparticle diffusion was not the only rate-controlling step of adsorption process. Thermodynamic parameters revealed the feasibility, spontaneity, and endothermic nature of adsorption. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47728.     

Extension of the pore diffusion approach for modelling binary adsorption of lead and arsenic ions in a fixed‐bed column packed with atlantic cod fish scales

The removal of lead and arsenic ions using Atlantic Cod (Gadus morhua) fish scale involves ion exchange, chemisorption, and precipitation of its constituents and is competitive with respect to adsorption onto the negatively charged heterogeneous substrates. The nonlinear sorption equilibrium concept is preceded by pore diffusion of the solute and is utilised for numerical modelling of this binary adsorption. Numerical simulation data demonstrate reasonable agreements with experimental results of dynamic column tests. Sensitivity analyses confirm that parameters such as porosity, adsorption coefficient, mobility of ions, and number of sorption sites contribute significantly to breakthrough interval of contaminant in dynamic columns. At lower pH values (7–8.04), the adsorption coefficients of cations such as lead are significantly lower than at pH value of 11.0.     

Preparation of amidoxime‐modified polyacrylonitrile nanofibrous adsorbents for the extraction of copper(II) and lead(II) ions and dye from aqueous media

Amidoxime‐modified polyacrylonitrile nanofibrous films (AOPAN NFs) were prepared via an electrospinning technique. The traditional preparation methods for amidoximated polyacrylonitrile (AOPAN) solution were changed and improved. First, the PAN solution was modified by hydroxylamine hydrochloride to produce an AOPAN solution, and then, a small amount of inhibitor was added to the AOPAN solution for electrospinning. We found that the crosslinking of the AOPAN solution was inhibited by the addition of a small amount of inhibitor; at the same time, the storage time of the AOPAN solution was prolonged. In addition, the prepared AOPAN solution was electrospun into nanofibrous films, which could be used as excellent adsorption materials for Cu(II), Pb(II), and methyl orange (MO) after drying. The maximal adsorption capacities for Cu(II), Pb(II), and MO were 143.47, 178.57, and 68.07 mg/g, respectively. The adsorption capacities of the nanofibrous films were more than 50% that of the first adsorption after four recycling runs; this indicated the reusability of the nanofibrous films for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45697.     

Parameter optimization for the oxidative coupling of methane in a fixed bed reactor by combination of response surface methodology and computational fluid dynamics

A resource and time saving method is introduced for optimizing fixed bed reactors by the combination of response surface methodology (RSM) and CFD simulation. This is demonstrated for the oxidative coupling of methane (OCM) based on the reaction kinetics by Stansch et al. (1997). Firstly, a parameter screening is performed to identify the power factors modified reaction time, heating temperature and CH₄ to O₂ ratio. Secondly, utilizing Central Composite Design, meta models for the most interesting responses are developed, i.e. C₂ selectivity and yield as well as CH₄ conversion. The statistical models describe the characteristics of the responses over a wide range. Thirdly, an optimization of C₂ yield is carried out using RSM. The maximum is detected to be approx. 14% and validated by three dimensional CFD simulations. In the investigated parameter space the optimized parameter conditions are found for a feed composition of 20% nitrogen, 26.7% oxygen, 53.3% methane (CH₄ to O₂ ratio of 2), a modified reaction time of 61 kg s/m³ and a heating temperature of 801.5 °C.     

Removal properties of crosslinked poly(2‐acrylamido glycolic acid) for trace heavy metal ions: Effect of pH,temperature, contact time,and salinity on the adsorption behavior

Crosslinked poly(2‐acrylamido glycolic acid) resin was synthesized by radical polymerization. This resin contains three potential ligand groups and was studied as an adsorbent of trace heavy metal ions from a saline aqueous solution and sea water by using the Batch equilibrium procedure. Adsorption characteristics of the resin toward Cu(II), Ni(II), Cd(II), and Pb(II) were studied spectrophotometrically, both in competitive and noncompetitive conditions. The effect of pH, contact time, amount of sorbent, temperature, and salinity were studied. The resin showed a high affinity particularly for Ni(II). It was possible to remove completely Ni(II) and Pb(II) from the resin by 4M HNO₃. The retention properties of the resin were also investigated for Cu(II) contained in natural sea waters. The retention behavior was similar to that of the synthetic metal ion aqueous solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2614–2621, 2003     

Polymeric organogel as an effective approach for eradication of heavy metal ions As,Pb, Cd,and Cr from the surface of groundwater through adsorption stratagem

Excess metal pollutant has affected and caused serious havoc in the lives of terrestrial as well as aquatic beings. The core of this work revolves around eradicating highly toxic heavy metal ions from underground water systems using a cost-effective, high removal efficiency polymeric adsorbent capable of adsorbing and removing ionic metals whose backbone is composed of a bio-degradable polymer, polyvinyl alcohol. The obtained adsorbent was characterized using FT-IR, HNMR, and P-XRD. Morphological studies were carried out using SEM. Detection and adsorption of metal ions were performed using SEM–EDX and AAS; wherein the adsorbent was found to remove nearly 80% of arsenic ions, 70.5% and 70.7% for lead and chromium ions while 60.7% for cadmium ions, respectively. Further, the kinetics of adsorption along with intraparticle diffusion studies were also performed to determine the mechanism alongside observing the isothermal influence of the sorbent. The adsorption capacity was seen to be highest in arsenic at around 570.42 mg g⁻¹ thus acting as a potential and effective adsorbent for the removal of heavy metal ions from groundwater.