Fixed-bed Sorption Processes Research Articles

UTILIZATION OF THOMAS MODEL TO PREDICT THEBREAKTHROUGH CURVES FOR ADSORPTION AND IONEXCHANGE

Fixed bed sorption processes such as adsorption and ion exchange do not operate at steady state. The design equations are differential that usually require numerical methods to solve. Thomas gives a general analytical solution for these equations. It is based on second-order reaction kinetics and the assumption of Langmuir isotherm. Computer program for the solution of Thomas model was designed using MATLAB 7.0. Four sets of experimental data are tested to show the capability of Thomas model to predict the breakthrough curves for adsorption and ion exchange processes. These data represent the sorption of o-cresol from water by activated carbon, acetic acid from air by activated carbon, phenol from water by natural zeolite, and trichloroethylene from air by zeolite- 5A.The results show that there are a good agreement between the experimental data and the model.

Kinetics of Fixed Bed Sorption Processes

Adsorption and ion exchange are examples of fixed-bed sorption processes that show transient behavior. This means that differential equations are needed to design them. As a result, numerical methods are commonly utilized to solve these equations. The solution frequently used in analytical methods is called the Thomas solution. Thomas gave a complete solution that adds a nonlinear equilibrium relationship that depends on second-order reaction kinetics. A computational approach was devised to solve the Thomas model. The Thomas model's validity was established by conducting three distinct sets of experiments. The first entails the adsorption of acetic acid from the air through the utilization of activated carbon. Following this, zeolite-5A adsorbs trichloroethylene (TCE) from the air. Finally, activated carbon is employed for the purpose of adsorbing o-cresol from aqueous solutions. A study was done to estimate phase equilibria and interphase mass transfer rates. To find the kinetic mass-transfer coefficient (K) for gases, the phase coefficients for mass transfer in the fluid phase ( ) and the pore phase ( ) were added together. The estimation of (K) for liquid was performed using the mass transfer coefficient for the solid phase and togather. The results suggest that the adsorption of acetic acid from air on activated carbon gives a good agreement with the Thomas model. The other sets of data demonstrate a disparity due to the underlying assumptions inherent in the Thomas model.

Arsenite and Arsenate Removal from Contaminated Groundwater by Nanoscale Iron–Manganese Binary Oxides: Column Studies

Abstract Fixed-bed sorption process can be very effective at removing arsenic from contaminated groundwater. In this study, a continuous operation was demonstrated for the removal of both arsenite [As(III)] and arsenate [As(V)] from aqueous media in a column packed with nanoscale iron–manganese binary oxides (NIM). Treatment performance of the sorbent was quantified by upflow column experiments at different flow rates and bed depth. Bed depth service time model was used for the prediction of column service time, and the predicted values were compared with experimental values. A study of competing ions showed that silicate caused the greatest decrease in the As removal rate relative to phosphate and sulfate. Column regeneration studies were carried out for three sorption–desorption cycles using 0.1 M NaOH as the eluent, the NIM bed saturated with arsenic could be efficiently regenerated and reused. We found that NIM could be used for different types of real groundwater. This column study revealed that NIM ...

Experimental and modeling studies on the sorption breakthrough behaviors of butanol from aqueous solution in a fixed-bed of KA-I resin

Removal of biobutanol from acetone-butanolethanol (ABE) fermentation broth can be achieved by fixed-bed sorption by means of KA-I resin, and the relevant breakthrough curves would provide much valuable information to help design a continuous fixed-bed sorption process in field application. In the present study, the effects of several important design parameters, i.e., initial butanol concentration (C f: 3.0 ∼ 30.0 g/L), inlet flow rate (Q f: 0.5 ∼ 5.5 mL/min) and adsorbent bed height (Z: 4.2 ∼ 18.0 cm), on the adsorption breakthrough curves of KA-I resin in a fixed-bed column were investigated. It was found that the amount of adsorbed butanol at breakthrough point was increased with an increase in the value of C f and Z; and with decrease in the value of Q f. However, the maximum sorption capacities of butanol at saturated point were basically unchanged. Three well-established fixed-bed adsorption models, namely Thomas, Yoon-Nelson and Adams-Bohart, were applied to predict the breakthrough curves and to determine the characteristic parameters of fixed-bed column, which are the basis for the process design at a real scale. Good agreement between the theoretical breakthrough curves and the experimental result were observed using Thomas and Yoon-Nelson models.

Arsenic removal using a polymeric/inorganic hybrid sorbent

A fixed-bed sorption process can be very effective in removing trace concentrations of arsenic from contaminated groundwater provided: the sorbent is very selective toward both As(III) and As(V) species; the influent and treated water do not warrant any additional pre- or post- treatment; pH and composition of the raw water with respect to other electrolytes remain unchanged besides arsenic removal, and the sorbent is durable with excellent attrition resistance properties. In addition, the sorbent should be amenable to efficient regeneration for multiple reuse. This study reports the results of an extensive investigation pertaining to arsenic removal properties of a polymeric/inorganic hybrid sorbent. Each hybrid sorbent particle is essentially a spherical macroporous cation exchanger bead within which agglomerates of nanoscale hydrated Fe oxide (HFO) particles have been uniformly and irreversibly dispersed using a simple chemical–thermal treatment. The new sorbent, referred to as hybrid ion exchanger or HIX, combines excellent mechanical and hydraulic properties of spherical polymeric beads with selective As(III) and As(V) sorption properties of HFO nanoparticles at circum-neutral pH. Comparison of the results of fixed-bed column runs between the new sorbent and the polymeric anion exchanger confirmed that both As(V) and As(III) were removed very selectively with HIX. Equally important, no pH adjustment, pre- or post-treatment was warranted. Besides the absence of arsenic, the treated water composition was identical to that of influent water. HIX was amenable to efficient in situ regeneration with caustic soda and could subsequently be brought into service following a short rinse with carbon dioxide sparged water. During fixed-bed column runs, intraparticle diffusion was identified as the primary rate-limiting step for both As(III) and As(V) sorption. Repeated use of the same HIX particles during various laboratory investigations provided strong evidence that the new sorbent possesses excellent attrition resistance properties and retains its arsenic removal capacity over cycles.

Selective removal and recovery of phosphate in a novel fixed-bed process

This paper reports salient features of a new fixed-bed sorption process in regard to ultimate removal and recovery of phosphate from municipal and industrial wastewater. The sorbent, referred to as polymeric ligand exchanger(PLE), is essentially a copper(II) loaded specialty chelating polymer. Laboratory experiments have demonstrated that the PLE: can remove phosphate selectively from municipal and synthetic wastewater; is amenable to efficient regeneration; and provides opportunities to recover phosphate and reuse the spent regenerant for multiple numbers of cycles.

Selective removal and recovery of phosphate in a novel fixed-bed process

This paper reports salient features of a new fixed-bed sorption process in regard to ultimate removal and recovery of phosphate from municipal and industrial wastewater. The sorbent, referred to as polymeric ligand exchanger(PLE), is essentially a copper(II) loaded specialty chelating polymer. Laboratory experiments have demonstrated that the PLE: can remove phosphate selectively from municipal and synthetic wastewater; is amenable to efficient regeneration; and provides opportunities to recover phosphate and reuse the spent regenerant for multiple numbers of cycles.

Wave Propagation in Mass-Transfer Processes: From Chromatography to Distillation

We review the advancement of the dynamic theories based on wave propagation phenomena for two major classes of separation processes : fixed-bed sorption processes such as chromatography and countercurrent mass-transfer processes such as distillation. Aiming at providing a common perspective, we begin with a brief review of the fundamental physics of wave propagation in these processes with notations common to both classes. Then, for single-variance systems (with one independent component), we review the well-developed theories for fixed beds and, as the main focus, the recent efforts to adapt these theories to countercurrent processes, in particular, distillation. The last part reviews the equilibrium theories of multicomponent chromatography with emphasis on the coherent wave theory originated by Helfferich and briefly covers the most recent attempts to apply this theory to multicomponent countercurrent processes. The review is summarized with prospects of applying the wave propagation theory to distillation control and design

Characterizing a new class of sorptive/desorptive ion exchange membranes for decontamination of heavy-metal-laden sludges

Selective removal of small amounts (<5%) of heavy metal precipitates from the background of innocuous solids in a sludge or slurry system is a challenging separation problem. Conventional fixed-bed sorption processes and membrane separation processes are unable to handle sludges/slurries with high suspended solids (1-10%) contents. This study identifies and investigates a new type of composite sorptive/desorptive membrane made of fine particles of chelating polymers entrapped in thin sheets of porous poly(tetrafluoroethylene) (PTFE). These membranes are not fouled by high concentrations of suspended solids but retain the original properties of the chelating exchangers

General solutions of second-order kinetics for fixed-bed sorption processes

Application de la procedure mathematique developpee par Amundson (1950) en utilisant la methode de transformation de Laplace