Analysis Of Breakthrough Curves Research Articles

Magnetic resonance imaging reveals detailed spatial and temporal distribution of iron-based nanoparticles transported through water-saturated porous media

The application of engineered nanoparticles (ENP) such as iron-based ENP in environmental systems or in the human body inevitably raises the question of their mobility. This also includes aspects of product optimization and assessment of their environmental fate. Therefore, the key aim was to investigate the mobility of iron-based ENP in water-saturated porous media. Laboratory-scale transport experiments were conducted using columns packed with quartz sand as model solid phase. Different superparamagnetic iron oxide nanoparticles (SPION) were selected to study the influence of primary particle size (dP=20nm and 80nm) and surface functionalization (plain, –COOH and –NH2 groups) on particle mobility. In particular, the influence of natural organic matter (NOM) on the transport and retention behaviour of SPION was investigated. In our approach, a combination of conventional breakthrough curve (BTC) analysis and magnetic resonance imaging (MRI) to non-invasively and non-destructively visualize the SPION inside the column was applied. Particle surface properties (surface functionalization and resulting zeta potential) had a major influence while their primary particle size turned out to be less relevant. In particular, the mobility of SPION was significantly increased in the presence of NOM due to the sorption of NOM onto the particle surface resulting in a more negative zeta potential. MRI provided detailed spatially resolved information complementary to the quantitative BTC results. The approach can be transferred to other porous systems and contributes to a better understanding of particle transport in environmental porous media and porous media in technical applications.

On the formation of multiple local peaks in breakthrough curves

AbstractThe analysis of breakthrough curves (BTCs) is of interest in hydrogeology as a way to parameterize and explain processes related to anomalous transport. Classical BTCs assume the presence of a single peak in the curve, where the location and size of the peak and the slope of the receding limb has been of particular interest. As more information is incorporated into BTCs (for example, with high‐frequency data collection, supercomputing efforts), it is likely that classical definitions of BTC shapes will no longer be adequate descriptors for contaminant transport problems. We contend that individual BTCs may display multiple local peaks depending on the hydrogeologic conditions and the solute travel distance. In such cases, classical definitions should be reconsidered. In this work, the presence of local peaks in BTCs is quantified from high‐resolution numerical simulations in synthetic fields with a particle tracking technique and a kernel density estimator to avoid either overly jagged or smoothed curves that could mask the results. Individual BTCs from three‐dimensional heterogeneous hydraulic conductivity fields with varying combinations of statistical anisotropy, heterogeneity models, and local dispersivity are assessed as a function of travel distance. The number of local peaks, their corresponding slopes, and a transport connectivity index are shown to strongly depend on statistical anisotropy and travel distance. Results show that the choice of heterogeneity model also affects the frequency of local peaks, but the slope is less sensitive to model selection. We also discuss how solute shearing and rerouting can be determined from local peak quantification.

Fate of the antibiotic sulfadiazine in natural soils: Experimental and numerical investigations

Based on small-scale laboratory and field-scale lysimeter experiments, the sorption and biodegradation of sulfonamide sulfadiazine (SDZ) were investigated in unsaturated sandy and silty-clay soils. Sorption and biodegradation were low in the laboratory, while the highest leaching rates were observed when SDZ was mixed with manure. The leaching rate decreased when SDZ was mixed with pure water, and was smallest with the highest SDZ concentrations. In the laboratory, three transformation products (TPs) developed after an initial lag phase. However, the amount of TPs was different for different mixing-scenarios. The TP 2-aminopyrimidine was not observed in the laboratory, but was the most prevalent TP at the field scale. Sorption was within the same range at the laboratory and field scales. However, distinctive differences occurred with respect to biodegradation, which was higher in the field lysimeters than at the laboratory scale. While the silty-clay soil favored sorption of SDZ, the sandy, and thus highly permeable, soil was characterized by short half-lives and thus a quick biodegradation of SDZ. For 2-aminopyrimidine, half-lives of only a few days were observed. Increased field-scale biodegradation in the sandy soil resulted from a higher water and air permeability that enhanced oxygen transport and limited oxygen depletion. Furthermore, low pH was more important than the organic matter and clay content for increasing the biodegradation of SDZ. A numerical analysis of breakthrough curves of bromide, SDZ, and its TPs showed that preferential flow pathways strongly affected the solute transport within shallow parts of the soil profile at the field scale. However, this effect was reduced in deeper parts of the soil profile. Due to high field-scale biodegradation in several layers of both soils, neither SDZ nor 2-aminopyrimidine was detected in the discharge of the lysimeter at a depth of 1m. Synthetic 50year long simulations, which considered the application of manure with SDZ for general agricultural practices in Germany and humid climate conditions, showed that the concentration of SDZ decreased below 0.1μg/L in both soils below the depth of 50cm.

Influence of natural organic matter on fate and transport of silver nanoparticles in saturated porous media: laboratory experiments and modeling

Understanding the fate and transport of silver nanoparticles (AgNPs) is of importance due to their widespread use and potential harmful effects on humans and the environment. The present study investigates the fate and transport of widely used Creighton AgNPs in saturated porous media. Previous investigations of AgNP transport in the presence of natural organic matter (NOM) report contradictory results regarding how the presence of NOM affected the stability and mobility of AgNPs. In this work, a nonreactive tracer, AgNPs and a mixture of AgNPs and NOM were injected into a background solution (0.01 mM of NaNO3) flowing through laboratory columns packed with water-saturated glass beads to obtain concentration versus time breakthrough curves. Transport of AgNPs in the presence of NOM was simulated with a model that accounted for both reversible and irreversible attachment. Based upon an analysis of the AgNP breakthrough curves, it was found that addition of NOM at concentrations ranging from 1 to 40 mg L−1 resulted in significant decreases in both the zeroth and first moments of the breakthrough curves. These observations may be attributed to NOM promoting AgNP aggregation and irreversible attachment. Raman and surface-enhanced Raman scattering analysis of NOM-AgNP mixtures revealed that a possible interaction of NOM with AgNP occurred through the carboxylic moieties (–COO−) located in the immediate vicinity of the metallic surface. At higher concentrations of NOM, both the zeroth and first moments of the breakthrough curves increased. Based on modeling and the literature, we hypothesize that as the NOM concentration increases, it begins to coat both the AgNPs and the glass beads, leading to a situation where AgNP transport may be described in the same way that transport of a sorbing hydrophobic compound partitioning to an immobile organic phase is typically described, assuming reversible, rate-limited sorption.

Characterization of nanoparticle transport through quartz and dolomite gravels by magnetic resonance imaging

AbstractMagnetic resonance imaging (MRI) has tremendous potential for revealing transport processes in engineered and geologic systems. Here, we utilize MRI to image nanoparticle (NP) transport through a saturated coarse-grained system. Commercially available paramagnetically tagged NPs are used; the paramagnetic tag making the NP visible to MRI. NP transport was imaged as NPs migrated through packed columns of quartz and dolomite gravel. Changes in T2-weighted image intensity were calibrated to provide fully quantitative maps of NP concentration at regular time intervals (T2being the spin–spin relaxation time of1H nuclei). Transport of nanoparticles was significantly retarded in dolomite compared to quartz due to electrostatic attraction between nanoparticle and dolomite surfaces. NP concentration profiles were evaluated with the CXTFIT computer package to estimate nanoparticle transport parameters at multiple points along the length of the column. This provided temporally resolved parameters that standard breakthrough curve analysis cannot provide. Particle–surface interaction energy profiles were described through Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. While dispersion coefficients and fast deposition rate constant (kfast) were found to increase with distance, deposition rate constant (k) and collision efficiency (α) were found to decrease with distance. These length-dependant variations have significant scaling-up implications for transport models used to predict NP transport in natural and engineered coarse-grained systems, such as sustainable urban drainage systems and river beds.

Adsorption-coupled reduction of bromate by Fe(II)–Al(III) layered double hydroxide in fixed-bed column: Experimental and breakthrough curves analysis

In this study, the bromate removal was investigated in continuous fixed-bed column using Fe(II)–Al(III) layered double hydroxide (LDH). With increase of column bed depth from 1.0 to 3.0cm, breakpoint time (tb) increased from 51 to 175h while throughput volume raised from 12.24 to 42.00L at breakthrough point. The bromate removal was attributed to the reduction of Fe(II) present in LDH. The breakthrough curve was simulated well by Thomas model, but BDST model was the only effective to initial part (1–10%). The maximum removal capacity (N0) calculated by Thomas model reached 71.01μmol/g at flow rate (3mL/min).

Contaminant transfer and hydrodispersiveparameters in basaltic lava flows: artificial tracertest and implications for long-term management

Abstract The aim of this paper is to evaluate the vulnerabilityafter point source contamination and characterizewater circulations in volcanic flows located in theArgnat basin volcanic system (Chaîne des Puys, FrenchMassif Central) using a tracer test performed by injectinga iodide solution. The analysis of breakthrough curves allowedthe hydrodispersive characteristics of the massivelava flows to be determined. Large Peclet numbers indicateda dominant advective transport. The multimodal featureof breakthrough curves combined with high valuesof mean velocity and low longitudinal dispersion coefficientsindicated thatwater flows in an environment analogousto a fissure system, and only slightly interacts with alow porosity matrix (ne < 1%). Combining this informationwith lava flow stratigraphy provided by several drillingsallowed a conceptual scheme of potential contaminant behaviourto be designed. Although lava flows are vulnerableto point source pollution due to the rapid transfer of waterwithin fractures, the saturated scoriaceous layers locatedbetween massive rocks should suffice to strongly bufferthe transit of pollution through dilution and longer transittimes. This was consistent with the low recovery rate ofthe presented tracer test.

Nanoparticle transport in saturated porous medium using magnetic resonance imaging

Transport study of nanoparticle (NP) through matrix flow dominated aquifer sand and soils have significant influence in natural systems. To quantify the transport behaviour, magnetic resonance imaging (MRI) was used to image the iron oxide based nanoparticle, Molday ION (carboxyl terminated) through saturated sandstone rock core. T2-weighted images were acquired and the changes in image intensity were calibrated to get a quantitative concentration profiles at various time intervals. These profiles were evaluated through CXTFIT transport model to estimate the transport parameters. These parameters are estimated at various points along the length of the column while classical breakthrough curve analysis cannot provide these details. NP–surface interactions were investigated using DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. The dispersion coefficients (2.55–1.21×10−7m2/s) were found to be decrease with distance, deposition rate constant k (6.70–9.13×10−4(1/s)) and fast deposition rate constant kfast (4.32–8.79×10−2(1/s)) were found to be increase with distance. These parameter variations over length will have a scaling up impact in developing transport models for environmental remediation and risk assessment schemes.

Breakthrough Curve Analysis for Fixed-Bed Adsorption of Azo Dyes Using Novel Pine Cone—Derived Active Carbon

A novel activated carbon has been produced from pine cone, a sustainable resource, by phosphoric activation at 900 °C. The BET surface area of the activated carbon was 869 m2/g and the methylene blue isotherm area was 734 m2/g. The adsorption of two single-component acid azo dyes, Acid Blue 113 (AB113) and Acid Black 1 (AB1), onto this activated carbon was studied using fixed-bed adsorption. Breakthrough curves and equilibrium isotherms were obtained for the adsorption of these two dyes onto the prepared active carbon. The highest adsorption capacities achieved for AB113 and AB1 were 485 and 286 mg dye/g carbon, respectively. Two-column breakthrough curve models were applied to correlate the experimental adsorption breakthrough curves for each dye: the Thomas model, based on solid-phase internal diffusion, has been applied with considerable success; and the saturation isotherm model approach of Michaels was used with a reasonable degree of success.

Solute transport in periodical heterogeneous porous media: Importance of observation scale and experimental sampling

Summary This paper focuses on the effects of the observation scale and sampling on the dispersion of tracers in periodical heterogeneous porous media. A Model Heterogeneous Porous Medium (MHPM) with a high degree of heterogeneity was built. It consists of a preferential flow path surrounded by glass beads. 44 tracer experiments were carried out on several series of periodic MHPM to investigate the effect of the observation scale on solute dispersion. Each series was replicated several times, allowing for a statistical description of the unit transfer function of the MHPM. No significant trend was found for the dispersion coefficient as a function of the size of the MHPM. However, given the variability of the breakthrough curves from one experiment replicate to another, under-sampling might easily lead to conclude that the dispersion coefficient is variable with distance. Depending on the samples used, it would be as easy to (wrongly) detect an increasing trend as to detect a decreasing one. A confidence interval analysis of the experimental breakthrough curves in the Laplace space shows that (i) there exists a model with scale independent parameters that can describe the experimental breakthrough curves within the limits of experimental uncertainty, (ii) this model is not the advection–dispersion (AD) model, (iii) the modelling error of the AD model decreases with the number of periods, (iv) the size of the Reference Elementary Volume for the dispersion coefficient is between 10 and 20 periods. The effects of sampling prove to override those of scaling. This, with the invalidity of the AD model, leads to question attempts to calibrate and/or identify trends in the dispersion coefficient at intermediate scales from a limited number of experiment replicates.

Solute Transport through a Pine Bark-based Substrate under Saturated and Unsaturated Conditions

An understanding of how dissolved mineral nutrient ions (solutes) move through pine bark substrates during the application of irrigation water is vital to better understand nutrient transport and leaching from containerized crops during an irrigation event. However, current theories on solute transport processes in soilless systems are largely based on research in mineral soils and thus do not necessarily explain solute transport in soilless substrates. A study was conducted to characterize solute transport through a 9 pine bark:1 sand (by volume) substrate by developing and analyzing breakthrough curves (BTCs). Columns filled with pine bark substrate were subjected to the application of a nutrient solution (tracer) and deionized water under saturated and unsaturated conditions. Effluent drained from the columns during these applications was collected and analyzed to determine the effluent concentration (C) of the bulk ions in solution through electrical conductivity (EC) and nitrate (NO3–), phosphate, and potassium (K+) concentrations. The BTCs were developed by plotting C relative to the concentration of the input solution (Co) (i.e., relative concentration = C/Co) as a function of the cumulative effluent volume. Solutes broke through the column earlier (i.e., with less cumulative effluent) and the transition from C/Co = 0 to 1 occurred more abruptly under unsaturated than saturated conditions. Movement of the anion, NO3–, through the substrate was observed to occur more quickly than the cation K+. Throughout the experiment, 37% of the applied K+ was retained by the pine bark. The adsorption of K+ to pine bark cation exchange sites displaced calcium (Ca2+) and magnesium (Mg2+), of which the combined equivalent charge accounted for 43.1% of the retained K+. These results demonstrate the relative ease that negatively charged fertilizer ions could move through a pine bark substrate while solution is actively flowing through substrate pores such as during irrigation events. This approach to evaluating solute transport may be used in horticultural research to better understand how mineral nutrients move through and subsequently leach from soilless substrates during irrigation. Expanding this knowledge base may lead to the refinement of production practices that improve nutrient and water use efficiency in container nurseries.

Use of artificial and natural tracers to assess groundwater transit-time distribution and flow systems in a high-alpine karst system (Wetterstein Mountains, Germany)

Groundwater in mountainous karst regions is vital for regional water budgets and freshwater supply. Owing to increasing water demand and climate change, detailed knowledge of the highly heterogeneous alpine aquifer systems is required. Multi-tracer analyses have been conducted in the steep karstic Wetterstein Mountains, which includes Germany’s highest summit, Zugspitze (2,962 m asl). Results of artificial tracer tests demonstrate well-developed flow paths through the unsaturated zone (up to 1,000 m thickness). Flow paths cross topographic divides and contribute to deep drainage systems underneath alpine valleys. Cross-formational flow has been identified. Quantitative analysis of tailing-dominated breakthrough curves and stable isotopes (18O) has enabled determination of the mean transit-time distribution. A fast-flow component with transit times between 3 and 13 days was found in karst conduits and open fissures, dependent on flow conditions. An intermediate-flow component, showing mean transit times of about 2.9–4.9 months, was found in well-drained fissures and fractures. A slow-flow component with mean transit times greater than 1 year is attributable to slow flow and low storage in the poorly drained fissures and rock matrix. The conceptual model enables a better understanding of drainage, water resources and vulnerability of the high-alpine karst system.

Column dynamic studies and breakthrough curve analysis for Cd(II) and Cu(II) ions adsorption onto palm oil boiler mill fly ash (POFA)

This paper investigates the adsorption characteristics of palm oil boiler mill fly ash (POFA) derived from an agricultural waste material in removing Cd(II) and Cu(II) from aqueous solution via column studies. The performance of the study is described through the breakthrough curves concept under relevant operating conditions such as column bed depths (1, 1.5, and 2 cm) and influent metal concentrations (5, 10, and 20 mg/L). The Cd(II) and Cu(II) uptake mechanism is particularly bed depth- and concentration-dependant, favoring higher bed depth and lower influent metal concentration. The highest bed capacity of 34.91 mg Cd(II)/g and 21.93 mg Cu(II)/g of POFA was achieved at 20 mg/L of influent metal concentrations, column bed depth of 2 cm, and flow rate of 5 mL/min. The whole breakthrough curve simulation for both metal ions were best described using the Thomas and Yoon–Nelson models, but it is apparent that the initial region of the breakthrough for Cd(II) was better described using the BDST model. The results illustrate that POFA could be utilized effectively for the removal of Cd(II) and Cu(II) ions from aqueous solution in a fixed-bed column system.

Mobility and Interaction of Heavy Metals in a Natural Soil

We study the mobility and interaction under competing conditions observed for copper (\(\text{ Cu}^{2+}\)) and zinc (\(\text{ Zn}^{2+}\)) ions in the context of laboratory-scale experiments performed in natural soil columns. The experiments focus on the analysis of solute breakthrough curves (BTCs) obtained after injection of an aqueous solution containing similar concentrations of the two metal ions into a soil column fully saturated with double deionized water. Transport of the competing ions is tested for the same soil under aerobic and anaerobic conditions. Measurements show that the species with lower affinity for the soil, \(\text{ Zn}^{2+}\), migrates occupying all available adsorption sites, and is then progressively replaced by the ion with higher affinity, \(\text{ Cu}^{2+}\). The two ions are displaced in the system with different effective retardation. The slowest species replaces the sorbed ions, resulting in observed \(\text{ Zn}^{2+}\) concentrations that display a non-monotonic behavior in time and which, for a certain period, are larger than the concentration supplied continuously at the inlet. In the absence of a complete geochemical characterization of the system, we show that the measured concentrations of both metals can be interpreted through simple models based on a set of coupled partial differential and algebraic equations, involving a small subset of aqueous and adsorbed species that are present in the system. Depending on the model considered, the relationship between aqueous and adsorbed ion concentrations is described at equilibrium by a Gaines–Thomas (GT) formulation, a competitive Sheindorf–Rebhun–Sheintuch (SRS) isotherm, or an Extended Langmuir (EL) isotherm, respectively. The GT formulation provides the best interpretation of the observed behavior among the models tested. We find that employing these simple models, which account only for the main governing reactive processes, allows reasonable estimation of the observed BTCs in experiments where only partial geochemical datasets are available.

Application of Polythiophene–Sawdust Nano-Biocomposite for Basic Dye Removal Using a Continuous System

A novel dye adsorbent was developed by a poly (3-methyl thiophene) nano layer coated onto sawdust obtained from Narra wood. The polymer was synthesized chemically under in-situ conditions on the surface of the sawdust. Methylene blue, a typical cationic textile dye, was employed as a test probe for adsorption experiments. The experiments were conducted in both batch and fixed-bed column systems. The effects of variables such as pH, initial dye concentration, flow rate, and bed height were investigated. The Thomas dynamic model was applied to calculate the sorption capacity of adsorbents. Based on the breakthrough curves analysis, the highest column capacity of 191 mg/g was obtained. The introduced nano-biocomposite was found to be more than seven times more efficient than unmodified sawdust for methylene blue removal. The regeneration of the modified sawdust is quite possible using 0.10 M HCl in ethanol as a washing solution with high efficiency.

Column Adsorption Studies for the Removal of Cr(VI) Ions by Ethylamine Modified Chitosan Carbonized Rice Husk Composite Beads with Modelling and Optimization

The objective of this present study is the optimization of process parameters in adsorption of Cr(VI) ions by ethylamine modified chitosan carbonized rice husk composite beads (EAM‐CCRCBs) using response surface methodology (RSM) and continuous adsorption studies of Cr(VI) ions by ethylamine modified chitosan carbonized rice husk composite beads (EAM‐CCRCBs). The effect of process variables such as initial metal ion concentration, adsorbent dosage and pH were optimized using RSM in order to ensure high adsorption capacity at low adsorbent dosage and high initial metal ion concentration of Cr(VI) in batch process. The optimum condition suggested by the model for the process variable such as adsorbent dosage, pH and initial metal ion concentration was 0.14 g, 300 mg/L and pH2 with maximum removal of 99.8% and adsorption capacity of 52.7 mg/g respectively. Continuous adsorption studies were conducted under optimized initial metal ion concentration and pH for the removal of Cr(VI) ions using EAM‐CCRCBs. The breakthrough curve analysis was determined using the experimental data obtained from the continuous adsorption. Continuous adsorption modelling such as bed depth service model and Thomson model were established by fitting it with experimental data.

Performance evaluation of different horizontal subsurface flow wetland types by characterization of flow behavior, mass removal and depth-dependent contaminant load

For several pilot-scale constructed wetlands (CWs: a planted and unplanted gravel filter) and a hydroponic plant root mat (operating at two water levels), used for treating groundwater contaminated with BTEX, the fuel additive MTBE and ammonium, the hydrodynamic behavior was evaluated by means of temporal moment analysis of outlet tracer breakthrough curves (BTCs): hydraulic indices were related to contaminant mass removal. Detailed investigation of flow within the model gravel CWs allowed estimation of local flow rates and contaminant loads within the CWs. Best hydraulics were observed for the planted gravel filter (number of continuously stirred tank reactors N = 11.3, dispersion number = 0.04, Péclet number = 23). The hydroponic plant root mat revealed lower N and pronounced dispersion tendencies, whereby an elevated water table considerably impaired flow characteristics and treatment efficiencies. Highest mass removals were achieved by the plant root mat at low level: 98% (544 mg m−2 d−1), 78% (54 mg m−2 d−1) and 74% (893 mg m−2 d−1) for benzene, MTBE and ammonium–nitrogen, respectively. Within the CWs the flow behavior was depth-dependent, with the planting and the position of the outlet tube being key factors resulting in elevated flow rate and contaminant flux immediately below the densely rooted porous media zone in the planted CW, and fast bottom flow in the unplanted reference.

Adsorption Behavior of Hydrogen and Deuterium on Natural Mordenite Adsorbent at 77 K

Cryogenic adsorption is effective for the recovery of low-concentration hydrogen isotopes in bulk helium gases. In a fusion power plant, application of this process is foreseen for the recovery of tritium from the blanket sweep gas and cleanup of the helium discharge exhaust gas. The authors performed a screening test to find more suitable adsorbents for the recovery of hydrogen isotopes from the bulk helium gas at liquid nitrogen temperature. The screening test indicated that a natural mordenite adsorbent has a quite high adsorption capacity for hydrogen under a helium atmosphere. For the adsorption of deuterium, it was found that the natural mordenite adsorbent possesses a high adsorption capacity even at the lower pressure range of hydrogen and deuterium. The adsorption rates of hydrogen and deuterium were quantified by analyzing breakthrough curves obtained in experiments. Evaluated effective pore diffusivities of hydrogen isotopes in the mordenite adsorbents are considerably higher than those in MS5A adsorbents. Thus, it can be said that the natural mordenite adsorbents are suitable for adsorption of hydrogen isotopes from the viewpoint of adsorption rates, as well. The results suggest that mordenite-type adsorbents are promising for the recovery of low-concentration hydrogen isotopes from the helium bulk gas.

Non-destructive evaluation of an activated carbon using microwaves to determine residual life

This paper describes a novel technique for determining the residual life of activated carbon material through changes in response when placed inside a resonant cylindrical cavity excited at microwave frequencies. The technique has been validated through the co-ageing of two activated carbon batches at 40°C and 80% relative humidity over a period of 7months. Two regions in the microwave spectra, 7500 and 8595MHz, have been identified to exhibit similar transmitted signal attenuation: 0.25 and 0.35dBm/month, respectively. Breakthrough curve analysis using (CN)2, CNCl and HCN confirmed that the samples were indeed deteriorated over the experimental period. Since activated carbon derives its filtration properties from both porosity and impregnants contained in the structure, the results obtained here suggest that there is a strong correlation between the response of activated carbon at microwave frequencies and amount of time that the activated carbon is exposed to a humid atmosphere. As a result, it is possible to produce calibration curves which can be used to predict the residual life of the activated carbon material in real-time.

Separation of phenylalanine and tyrosine by ion-exchange using a strong-base anionic resin. I. Breakthrough curves analysis

Dynamics of separations of the amino acids phenylalanine and tyrosine in fixed-bed ion-exchange column using the strongly basic resin PA 316 was investigated for different operating conditions. The flow rate, feed amino acid concentration and pH solution affect significantly the breakthrough time of the saturations curves. A mathematical model which takes into account axial dispersed plug flow, external and intraparticle mass transfer resistances, as well as non-constant selectivity coefficient data, enabled successfully to simulate the experimental breakthrough curves. The model was satisfactorily extended to prediction of the experimental dynamic behaviour of phenylalanine (Phe) and tyrosine (Tyr) mixtures where the ratio of the feed concentrations of both amino acids was changed. A most effective separation of the amino acids was achieved when the concentration of Phe in the feed solution is higher than that of Tyr.