Batch Adsorption Systems Research Articles

Direct Red 28 Adsorption on Amosil and Avena sativa L.: Mass Transfer and Kinetics Modelling on the Solid/Solution Interface

Adsorption kinetics is a key issue for successful sorbent selection and the proper design of batch and fixed-bed adsorption systems. The aim of the present study was to determine the kinetics, mass transfer and diffusion coefficients and to establish the rate-controlling mechanism/s during Direct Red 28 adsorption on Amosil and Avena sativa L. biomass. Five kinetic models (pseudo-second order, Blanchard, Avrami, Ritchie and power function) and and four mass transfer (external diffusion, film diffusion, particle diffusion, intraparticle diffusion) mathematical models were applied to the experimental data. To confirm the best-fitting model(s), error analyses were conducted. The integrative comparative analyses of the values of the predicted model parameters, coefficients and error functions established that the intraparticle diffusion model best represented the experimental results of the dye sorption on dried A. sativa L. biomass, while for the Direct Red 28/Amosil system, the kinetic behavior is the best described by either the pseudo-second or Blanchard’s model. Boyd’s effective intraparticle diffusion coefficient (D i ), characterizing the dye sorption on Amosil, is significantly lower than that for the system Direct Red 28/A. sativa L. biomass. The low values of the Bi number (Bi < 0.5) suggests that the mass transfer resistance, for both systems, is concentrated at the fluid/solid phase surface.

Optimization of atrazine and imidacloprid removal from water using biochars: Designing single or multi-staged batch adsorption systems.

Contamination of surface and ground water by pesticides from agricultural runoff and industrial discharge is one of the main causes of aqueous contaminations world over. Biochar, agricultural waste derived highly aromatic substance produced after pyrolysis and carbonification of biomass have exhibited good adsorption capacity for pesticides and can be used to develop on-site bio-purification systems for organic contaminant removal from polluted waters. However, high amounts of adsorbent required in single stage-batch sorption plant increases the cost of water treatment; therefore, multistage plant systems were investigated. Normal (RSBC) and phosphoric acid treated (T-RSBC) rice straw biochars were evaluated for atrazine and imidacloprid sorption and data fitted to the Freundlich isotherm. The adsorption data was modelled to develop single or multi-staged adsorber plants for pesticide removal from water. Both biochars showed significantly high adsorption capacity for imidacloprid and atrazine. Modelling studies using the Freundlich adsorption parameters suggested that the amounts (kg/1000L) of RSBC and T-RSBC for 95% of atrazine removal (10mg/L) in single-, two- and three-staged adsorber plant models were 8.84, 2.44, 1.61kg and 4.47, 1.42, 0.98kg, respectively. Corresponding amounts for 95% imidacloprid removal (10mg/L) were 3.97, 1.22, 0.84kg and 3.98, 1.38, 0.96kg, respectively. Thus, the two-staged model suggested 65-72% reduction in amount of adsorbent required over the single stage model, while the three-staged model suggested 30-34% adsorbent saving over the two-staged plant model. Single and two-staged adsorber plant model findings were validated for atrazine removal using T-RSBC. Results suggested that amounts calculated using modelling studies were fairly accurate. Biochars, as low cost adsorbents for atrazine and imidacloprid removal from contaminated water, can be used to develop low cost adsorber plants based on multiple batch sorption systems for the removal of these pesticides. Upscaled use of the 2-stage adsorber plant model will substantially reduce the cost of the treatment process, especially at pesticide concentration <10mg/L as lesser amounts of biochar will be used for treatment process.

Insight into the adsorption kinetics models for the removal of contaminants from aqueous solutions

Abstract The past decade has seen a boom in environmental adsorption studies on the adsorptive removal of pollutants from the aqueous phase. A large majority of works treat kinetic modeling as a mere routine to describe the macroscopic trend of adsorptive uptake by using common models, often without careful appraisal of the characteristics and validity of the models. This review compiles common kinetic models and discusses their origins, features, modified versions (if any), and applicability with regard to liquid adsorption modeling for both batch adsorption and dynamic adsorption systems. Indiscriminate applications, ambiguities, and controversies are highlighted and clarified. The appropriateness of linear regression for correlating kinetic data is discussed. This review concludes with a note on the current scenario and the future of kinetics modeling of liquid adsorption.

Synthesis of ordered mesoporous SBA-15 and its adsorption of methylene blue

The removal of methylene blue (MB) dye pollutant from synthetic wastewater onto mesoporous SBA-15 was studied in batch adsorption systems. The characterization for the prepared adsorbent such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), BET surface area and Fourier transform infrared (FTIR) spectroscopy was achieved. The experiments were carried out to measure the adsorption capacity as a function of contact time, initial concentration (40-110 mg/L), pH (3-11) and adsorbent dose (0.1-2.3 g/L). The equilibrium of the process was achieved within 20 min. Adsorption isotherms were fitted with the Langmuir, Freundlich and Temkin models. The equilibrium data were better represented with Langmuir Isotherm model. The kinetics of the MB sorption on SBA-15 was examined by using pseudo-first and pseudo-second order kinetics models. The kinetics analysis showed that the overall adsorption process was successfully fitted with the pseudo-second-order kinetic model. Good linearization of the data was observed for the initial phase of the reaction in accordance with expected behavior of intraparticle diffusion as the rate-limiting and rate-controlled step. SBA-15 can be effectively recovered by calcinations and reused fourteen times in batch system without significant loss in removal of methylene blue from aqueous solution.

Comparison of the efficiency of mesoporous silicas as absorbents for removing naphthalene from contaminated water

Mesoporous silicas MCM-48 and SBA-15 were synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Adsorption capacity of two mesoporous silica for removing naphthalene from waste water was determined. The results indicate that under similar conditions, SBA-15 had a better adsorption capacity than MCM-48. In this context, SBA-15 was modified using 3-aminopropyltrimethoxysilane and the effect of contact time, adsorbent dose, solution pH and concentration of naphthalene was investigated in batch adsorption systems. Solution pH appeared to be a key factor affecting the adsorption of naphthalene by NH2-SBA-15. The adsorption experiments revealed that a higher percentage of up to 79.3% of naphthalene was adsorbed in highly acidic media (pH of 2). The equilibrium data were analyzed using Langmuir and Freundlich isotherms and nonlinear regression analysis. This revealed that based on the correlation coefficient (R2 = 0.979) the Langmuir model provided the best fit to the results. The adsorption kinetic was determined using the pseudo-first order, pseudo-second order and Elovich kinetic models. Of the kinetics models tested, the pseudo-first-order equation provided the best fit to the results (R2 = 0.991) of the absorption of naphthalene by the adsorbent.

Desulfurization of diesel fuels by selective adsorption on activated carbons: Competitive adsorption of polycyclic aromatic sulfur heterocycles and polycyclic aromatic hydrocarbons

Adsorptive affinity of polycyclic aromatic sulfur heterocycles (PASHs) and polycyclic aromatic hydrocarbons (PAHs) on activated carbons and the effect of PAHs on the adsorption performance of PASHs were studied. Adsorptions of real and model diesels (MDs) containing aromatics and sulfur compounds over several activated carbons were conducted in both batch and fixed-bed adsorption systems. The adsorption results showed that adsorptive affinities of molecules with polycyclic aromatic skeleton structure are primarily governed by the π–π dispersive interaction between the aromatic rings and the graphene layers of activated carbons. In addition, the electron donor–acceptor mechanism also plays an important role for S-containing molecules. Furthermore, for effective adsorption of large molecules, not only the pore size of the adsorbent should be, at least, larger than the critical diameter of the adsorbate, but also the pore size should also be sufficiently large to reduce diffusional resistance during adsorption. Based on this studies, it can be concluded that the adsorption selectivity increases as follows: naphthalene < fluorene < dibenzothiophene < 4,6-dimethyl dibenzothiophene < anthracene < phenanthrene. The adsorption capacity of PASHs decreases significantly in the presence of PAHs as result of the adsorption competition due to similar structure, molecular diameter and adsorption mechanisms.

Abatement of Cr(VI) rich wastewater in a novel multistage External Loop Airlift Reactor using acidified activated carbon

In the present investigation, a multistage External Loop Airlift Reactor (ELALR) has been used for the treatment of Cr(VI) rich wastewater using acidified activated carbon as the adsorbent. The multistaging has been achieved by hydrodynamically induced continuous bubble generation, break-up and regeneration. The continuous rupture and bursting of bubbles creates localised turbulence and recirculation, which helps in faster transfer of Cr(VI) to the active sites of the solid adsorbents. The effect of different process parameters like contact time, adsorbent dose, superficial gas velocity on the removal of Cr(VI) was studied and it was found that the removal time for this system is quite lower as compared with simple batch adsorption systems. The kinetic data were fitted to the models of intra-particle diffusion, pseudo-second-order, and Lagergren, and followed more closely the Lagergren pseudo-first-order model.

Evaluation of Chemically Selective Displacer Analogues for Protein Purification

A library of molecular analogues to the selective displacer, N'1'-(4-methylquinolin-2-yl)ethane-1,2-diamine dinitrate, was employed to study the effects of changes in displacer chemistry on their efficacy for selective separations. High throughput screens were carried out using a robotic liquid handling system to examine the ability of these compounds to selectively displace proteins in batch adsorption systems. Experiments were conducted using the model protein pairs ribonuclease A/alpha-chymotrypsinogen A and cytochrome C/lysozyme on a strong cation exchanger. Selectivity pathway and DC-50 plots were constructed from the analogue screen data, and results indicated that minor changes in the molecular design of the displacer can have a significant impact on the separation behavior. Specifically, charge density and spacing of resin and protein interaction moieties were found to be important. The screen also identified a new displacer, 4-methyl-2-piperazin-1-yl-quinoline, which produced a more selective displacement than previously reported with the original compound. A steric mass action dynamic affinity plot was constructed to validate that this new displacer was acting as a chemically selective, rather than a steric mass action selective displacer. Finally, saturation transfer difference NMR experiments were conducted to examine protein-displacer interactions with these displacers and protein pairs. These results demonstrate how subtle changes in displacer design can be employed to fine-tune the separation performance of chemically selective displacers.

Preparation of Organic Sulfur Adsorbent from Coal for Adsorption of Dibenzothiophene-type Compounds in Diesel Fuel

High-performance organic sulfur adsorbents (OSA) have been prepared from coal by chemical activation for selective adsorption of the refractory sulfur compounds, such as 4-methyl dibenzothiophene and 4,6-dimethyldibenzothiophene, in diesel fuel. The performance of the prepared OSAs for adsorptive desulfurization (ADS) was evaluated in batch and flow adsorption systems at room temperature using a model diesel fuel. It was found that coal rank and preparation conditions, including activation agents (NaOH, KOH, and NaOH + KOH) and their ratio to coal, activation temperature, and time have significant impacts on the yield and ADS performance of the OSAs. The high-performance OSAs can be prepared from different ranks of coal by using NaOH + KOH as an activation agent with an activating-agent-to-coal ratio of 3.5. The yield of OSA increased in the order of lignite < high volatile bituminous coal < medium volatile bituminous coal < anthracite. The OSA-A, which was derived from an anthracite with the highest yiel...

Biosorption of Rhodamine B and Malachite green from aqueous solutions by Tamarindus indica fruit shells

The removal of rhodamine B and malachite green from aqueous solutions was studied in batch adsorption systems using Tamarindus Indica fruit shells as sorbents. The well known Freundlich, Langmuir and Redlich-Peterson isotherm equations were applied to the equilibrium sorption data obtained. The sorption dynamics were found to obey the pseudo-second order rate equation and particle diffusions appear to control the overall rates. Increase of both pH and temperature resulted in increased sorption and the thermodynamic parameters like ΔG, ΔH and ΔS were evaluated.

Treatment of phenolic wastewater in a novel multi-stage external loop airlift reactor using activated carbon

In this work, a novel multi-stage external loop airlift reactor has been designed to remove phenol from wastewater by means of its adsorption onto the surface of activated carbons. The multi-staging has been achieved by hydrodynamically induced continuous bubble generation, breakup and regeneration. The continuous rupture and bursting of bubbles creates localized turbulence and recirculation, which helps in faster transfer of trace pollutants to the active sites of the solid adsorbents. Thus, the pollutants get adsorbed to the surface of the solid adsorbents due to continuous agitation. Different operating parameters that affect the performance of the reactor are the superficial gas velocity, liquid circulation velocity, concentration of the pollutant present in wastewater, contact time and the carbon loading. The results show that the removal time as well as the activated carbon loading for this system were quite lower as compared to simple batch adsorption systems. The kinetic data were fitted to the models of intra-particle diffusion, pseudo-second-order and Lagergren, and followed more closely the Lagergren pseudo-first-order model. Langmuir and Freundlich models were used to study the adsorption isotherms. A correlation has been developed to predict the efficiency of percentage removal of phenol and found to be highly significant from statistical point of view.

Pore diffusion: Dependence of the effective diffusivity on the initial sorbate concentration in single and multisolute batch adsorption systems

The present work studies the intraparticle diffusivity in batch adsorption systems as a function of the initial sorbate concentration. The systems under investigation are basic dyes, namely Basic Blue 69, Basic Red 22 and Basic Yellow 21 and their binary and ternary combinations, all adsorbing onto activated carbon Filtrasorb 400. They study is based on the film-pore diffusion model and the output is a combination of the external mass transfer coefficient, kf and the effective diffusivity, Deff that yields congruent experimental and theoretical kinetic data. It has been found the Deff varies with Co in an exponential decay function. Furthermore. Deff values undergo a general reduction in the multisolute systems compared to the single component systems. Also, the relative diffusion rates in the multisolute systems are found to change such that Deff of the slower diffuser is enhanced and that Deff of the faster diffuser is inhibited.

High Throughput Determination and QSER Modeling of Displacer DC‐50 Values for Ion Exchange Systems

In this paper, the displacer concentration required to displace 50% of proteins bound in batch adsorption systems, DC‐50, was employed as a means of ranking high‐affinity, low molecular weight displacers for ion‐exchange systems. A relatively large data set of cationic displacers with varying chemistries were evaluated with two proteins on two strong cation exchange resins in parallel batch screening experiments. Using this methodology, a significant number of high affinity displacers were identified that could displace both proteins at relatively low concentrations. In addition, the DC‐50 data was used in concert with molecular structural information of the displacers to produce predictive quantitative structure‐efficacy relationship (QSER) models based on a support vector machine (SVM) regression approach. The resulting models were well correlated and the predictive power of these models was demonstrated. Examination of the features selected in these models provided insight into the factors influencing displacer efficacy in cation exchange systems. These results demonstrate the utility of a combined DC‐50/QSER approach to identify and design high‐affinity displacers for ion‐exchange displacement chromatography.

Consistency of Energy and Material Balances for Bidisperse Particles in Fixed-Bed Adsorption and Related Applications

This paper develops material and energy balances for fixed-bed adsorption of a multicomponent nonideal gas in bidisperse particles by defining enthalpies from thermodynamic paths chosen such that the reference states are an ideal gas for the fluid-phase and adsorbate-free solid for the adsorbent. The balances are developed in detail for a three-domain system: nanoporous domains, macropore space, and interstitial fluid. It is also shown that material and energy balances may be easily developed from the same enthalpy definitions for use in batch, stirred tank, or moving-bed adsorption systems. Material balances are developed first and are subsequently used to simplify the energy balances such that terms involving reference states cancel out of the equations. Simplifying assumptions are applied to the final equation set to obtain equations that resemble, but are somewhat different from, frequently used forms. A major difference, resulting from the use of thermodynamic paths, is often found in the treatment of heat capacities and heats of adsorption.

Pore-Surface Diffusion Model for Batch Adsorption Processes

A new pore-surface diffusion model (PSDM) for batch adsorption systems has been developed. The new PSDM incorporates pore and surface diffusion into a variable effective diffusion coefficient, but the contributions from both pore and surface diffusion are evaluated independently. This model is compared with two previous models, which were based on a “lumped” effective diffusion coefficient, for which rapid analytical solutions have been developed. A further advantage of the new model is that it incorporates a time dependent surface diffusivity based on surface adsorbate concentration. Previous rapid analytical solutions to the effective pore diffusion models have assumed a constant time independent surface adsorbate concentration. The three models have been compared using four sets of experimental data for the batch adsorption of dyes onto wood and peat.

Pore-Surface Diffusion Modeling for Dyes from Effluent on Pith

A new pore-surface diffusion model (PSDM) for batch adsorption systems based on shrinking core theory has been developed. The new PSDM incorporates pore and surface diffusion into a variable effect...

Solution to the homogeneous surface diffusion model for batch adsorption systems using orthogonal collocation

A solution to the homogeneous surface diffusion model has been developed and incorporated into a batch adsorption model based on external boundary layer mass transport and homogeneous diffusion. The model has been extensively tested using three experimental adsorption systems, namely, phenol on carbon, basic yellow dye on carbon and basic blue dye on silica. The effect of initial solute concentration and adsorbent mass has been studied in 23 batch experiments, which have been modelled using the collocation solution method to solve the homogeneous surface diffusion equation. The theoretical concentration decay curves show a high degree of correlation with experimental data.

Study of the mechanism of pore diffusion in batch adsorption systems

AbstractIn this study the film‐pore diffusion model was applied to describe system transport kinetics of three basic dye‐carbon systems, namely Basic Blue 69, Basic Red 22 and Basic Yellow 21. The mass transfer parameters evaluated were the external mass transfer coefficient kf (cm s−1) and the effective diffusivity Deff (cm2 s−1).A single kf value was sufficient to describe each dye system: these were 0.15 × 10−2, 0.20 × 10−2 and 0.50 × 10−2 cm s−1 for BB69, BR22 and BY21, respectively. The effective diffusivity was found to have values much larger than those of pore diffusivities calculated from liquid diffusivities and its value decreased with increasing initial dye concentration. This was attributed to the effect of surface diffusion, hence pore diffusivity was exchanged by the effective pore diffusivity in the model.The present model was solved by the exponential curve fit technique; results were expressed in the form of experimental and theoretical Sherwood Numbers compared in terms of the residual.