Equilibrium Distribution Coefficients Research Articles

Study on Equilibrium Distribution Coefficients during Osmotic Dehydration of White Gourd Slices

Equilibrium distribution coefficients were obtained to understand osmotic dehydration mechanism and to optimize and control osmotic dehydration process. The equilibrium distribution coefficients of white gourd slices were determined during osmotic dehydration at different temperatures (30–50C) and maltose syrup concentrations (40–60%, w/w). Equilibrium distribution coefficients as a function of temperature and maltose syrup concentration were modeled using nine nonlinear models. The results showed that the equilibrium distribution coefficients of water and solids ranged from 0.3411 to 0.8406 g/g and from 1.2392 to 1.5754 g/g, respectively. The best models for the equilibrium distribution coefficients of water and solids are, respectively, λse = −0.8345 + 0.0281T + 6.5665C − 0.0627CT + 0.0001T2 − 4.9081C2 + 0.0004T2C2 [R2 = 0.9899, sum of squared error (SSE) = 2.0511 × 10−4, root mean square error (RMSE) = 0.0143, χ2 = 9.2299 × 10−4, P = 2.10%], λse = −0.8345 + 0.0281T + 6.5665C − 0.0627CT + 0.0001T2 − 4.9081C2 + 0.0004T2C2 (R2 = 0.9734, SSE = 3.0827 × 10−4, RMSE = 0.0176, χ2 = 0.0014, P = 1.09%). Practical Applications Osmotic dehydration of white gourd slices in maltose syrup solution was investigated experimentally in different solution concentrations and at different temperatures. The equilibrium distribution coefficients of water and solids were calculated during osmotic dehydration of white gourd in maltose syrup solution. The equilibrium distribution coefficients of water and solids for white gourd slices as a function of maltose syrup concentration and temperature were investigated.

Batch Simulation of Multistage Countercurrent Extraction of Uranium in Yellow Cake from Monazite Processing with 5% TBP/Kerosene

In the processing of monazite ore to separate uranium, thorium and rare earth elements composed in the ore, uranium is first extracted and precipitated in the form of sodium diuranate (Na2U2O7) or yellow cake. This yellow cake requires further purification to remove thorium and traces of rare earth impurities from the cake. The extraction of uranium in 4N HNO3 with 5% TBP/kerosene extractant has been studied with a series batchwise extraction to simulate multistage countercurrent solvent extraction. Feed solutions were prepared from yellow cake obtained from the processing of monazite ore which has about 60% purity of uranium. Simulated continuous countercurrent extraction with 4, 5 and 6 extraction stages were carried out. Equilibrium distribution coefficients (D) of both uranium and thorium were found to decrease with increasing feed concentration and distribution coefficient of uranium is about 8.8 to 10.8 times higher than that of thorium. The highest distribution coefficient of uranium is 3.107 at uranium concentration of 3,182mg/L. Uranium recovery was found to increase from 83.76 to 90.91% with the increasing number of extraction stage from 4 to 5. Increasing of solvent to feed ratio from 1:1 to 2:1 also increases uranium recovery from 83.76 to 93.30%. However, purity of uranium obtained from most extraction seems to be limited at 93-94%. This suggests that a scrubbing process will be required to improve the purity of uranium in this extraction system.

Sorption of uranium from underground leaching solutions with highly basic anion exchangers

Sorption of U on strongly basic anion exchangers AMP, AM-p, Lewatit K6267, Lewatit MonoPlus MP600XL, Purolite A500u, and Purolite A600u was studied at various temperatures in batch and dynamic experiments. The dynamic exchange capacities, (g U) dm−3, of the anion exchangers to a breakthrough of 0.5 (mg U) dm−3 at 6–8°C were determined: AMP (9.56) > Purolite A600u (9.26) > Lewatit K6267 (9.13) > Purolite A500u, Lewatit MonoPlus MP600XL (8.87) > AM-p (5.88). Also, the total dynamic exchange capacities, (g U) dm−3, of the anion exchangers at 6–8°C were determined: AMP (37.13) > Purolite A500u (31.79) > Lewatit MonoPlus MP600XL (28.88) > Lewatit K6267 (27.74) > AM-p (27.58) > Purolite A600u (25.24). The concentration equilibrium distribution coefficients (Kd) of U on these resins were determined in batch experiments. The highest value of Kd = 2869 at 6°C and initial uranium concentration in solution of 65 mg dm−3 was attained with AMP of commercial grain-size distribution. At 24°C and the same uranium concentration, the highest value of Kd = 5195 was obtained with separated 0.8–1.0-mm fraction of AMP. The kinetic experiments were performed, and the internal diffusion step was found to be the limiting step of the U sorption with all the resins under consideration. The internal diffusion coefficients in ion exchanger grains were calculated to compare the resins with each other.

Deposition and transport of Pseudomonas aeruginosa in porous media: lab-scale experiments and model analysis

In this study, the deposition and transport of Pseudomonas aeruginosa on sandy porous materials have been investigated under static and dynamic flow conditions. For the static experiments, both equilibrium and kinetic batch tests were performed at a 1:3 and 3:1 soil:solution ratio. The batch data were analysed to quantify the deposition parameters under static conditions. Column tests were performed for dynamic flow experiments with KCl solution and bacteria suspended in (1) deionized water, (2) mineral salt medium (MSM) and (3) surfactant+MSM. The equilibrium distribution coefficient (Kd) was larger at a 1:3 (2.43 mL g−1) than that at a 3:1 (0.28 mL g−1) soil:solution ratio. Kinetic batch experiments showed that the reversible deposition rate coefficient (katt) and the release rate coefficient (kdet) at a soil:solution ratio of 3:1 were larger than those at a 1:3 ratio. Column experiments showed that an increase in ionic strength resulted in a decrease in peak concentration of bacteria, mass recovery and tailing of the bacterial breakthrough curve (BTC) and that the presence of surfactant enhanced the movement of bacteria through quartz sand, giving increased mass recovery and tailing. Deposition parameters under dynamic condition were determined by fitting BTCs to four different transport models, (1) kinetic reversible, (2) two-site, (3) kinetic irreversible and (4) kinetic reversible and irreversible models. Among these models, Model 4 was more suitable than the others since it includes the irreversible sorption term directly related to the mass loss of bacteria observed in the column experiment. Applicability of the parameters obtained from the batch experiments to simulate the column breakthrough data is evaluated.

Comparison of equilibrium and non-equilibrium distribution coefficients for the human drug carbamazepine in soil

The distribution coefficient (KD) for the human drug carbamazepine was measured using a non-equilibrium technique. Repacked soil columns were prepared using an Airport silt loam (Typic Natrustalf) with an average organic matter content of 2.45%. Carbamazepine solutions were then leached through the columns at 0.5, 1.0 and 1.5mLmin−1 representing average linear velocities of 1.8, 3.5 and 5.3cmh−1 respectively. Each flow rate was replicated three times and three carbamazepine pulses were applied to each column resulting in a total of 9 columns with 27 total carbamazepine pulses. Breakthrough curves were used to determine KD using the parameter fitting software CXTFIT. Results indicate that as flow rate decreased from 5.3 to 1.8cmh−1, KD increased an average of 21%. Additionally, KD determined by column leaching (14.7–22.7Lkg−1) was greater than KD determined by a 2h batch equilibrium adsorption (12.6Lkg−1). Based on these KD’s carbamazepine would be generally characterized as non-mobile in the soil investigated. However, repeated carbamazepine applications resulted in an average 22% decrease in KD between the first and third applications. Decreasing KD is attributed to differences in sorption site kinetics and carbamazepine residence time in contact with the soil. This would indicate that the repeated use of reclaimed wastewater at high application rates for long-term irrigation or groundwater recharge has the potential to lead to greater transport of carbamazepine than KD determined by batch equilibrium would predict.

Recovery of acetic acid from pre-hydrolysis liquor of hardwood kraft-based dissolving pulp production process by reactive extraction with triisooctylamine

Acetic acid was one of the main compositions of the pre-hydrolysis liquor (PHL), which was recovered by reactive extraction with triisooctylamine (TIOA) diluted with decanol. Dilution of TIOA played an important role in extracting acetic acid from the PHL. The recovery of acetic acid from the PHL by TIOA was increased from 10.34% to 66.60% with the dilution of TIOA to 20% by decanol at the HAc to TIOA molar ratio of 1, consequently, the equilibrium distribution coefficient KD increased. The effects of time, temperature and pH on the extraction process were also studied. The extraction process was very fast. The acetic acid extraction decreased from 65.13% to 57.34% with the rise of temperature to 50°C from 20°C. A higher pH increased the dissociation of acetic acid, as a result, decreased acetic acid extraction. The hemicelluloses in the PHL were unaffected on the extraction process of acetic acid.

Bond-graph description and simulation of agitated bulk liquid membrane system—Dependence of fluxes on liquid membrane volume

The transport properties of an agitated bulk liquid membrane (ABLM) were studied experimentally and theoretically as dependent on its volume (V(m)). The solution-diffusion pertraction under stationary, quasi-stationary, and non-stationary conditions was described using the methods of the pseudo-thermodynamic network analysis (TNA). It was found that the fluxes in the system depend on the membrane volume to the degree conditioned by the kinetics of interfacial phenomena, diffusion coefficients, and equilibrium distribution coefficients. In general, for the systems operations in batch regime, the maximum output fluxes (stripping rates, Jmax) observed under non-stationary or pseudo-stationary conditions are lower than these observed for the stationary-state system and are represented by the following empirical polynomial:logJmax=∑i=0nai(logV(m))iThe results of calculations were experimentally verified by a pertraction study of bromothymol blue or benzoic acid in the ABLM system with a bulk liquid membrane made of octane. The proposed model and numerical procedures can be applied for the prediction of ABLM efficiency as dependent on the operational conditions and physico-chemical characteristics of the system or for fitting experimental data.

Study on Segregation Process and Equilibrium Distribution Coefficients of Impurities during Zone Refining of Bibenzyl

The purification of commercial Bibenzyl by zone refining has been investigated with a view to establishing operational parameters and optimum processing conditions. Three factors are inspected, which are zone passing number, translation rate, and zone length. The axial profiles of product purity are determined. Meanwhile, the axial concentration profiles of four main impurities, which are Cyclohexylbenzene, Diphenylmethane, 1,1-Diphenylethane, and 1,2-Diphenylpropane have been also determined. The equilibrium distribution coefficients of the four impurities in Bibenzyl are calculated by measuring their effective distribution coefficients at zone travel rate of 4.97, 8.80, 11.89, and 17.43 mm/h. The results indicate that zone refining of Bibenzyl is very successful. The product purity can increase from 98.3466% to 99.8353% after 8 zone passes. The each additional zone pass and slower translation rate are helpful to purification of Bibenzyl. For 1 pass, longer zone length is better for purification of Bibenzyl. The equilibrium distribution coefficients of Cyclohexylbenzene, Diphenylmethane, 1,1-Diphenylethane, and 1,2-Diphenylpropane are 0.3917, 0.3677, 0.1687, and 3.8148, respectively.

Thermodynamic properties of the (Ba,Pb)SO4 solid solution under ambient conditions: Implications for the behavior of Pb and Ra in the environment

Despite numerous studies, the degree of non-ideality of the (Pb,Ba)SO4 solid solution has remained uncertain. Although there has been a tendency to interpret the linear variation of the unit cell parameters as a sign of ideal behavior, the lack of intermediate compositions in natural samples has led many authors to consider this solid solution to be non-ideal, with a positive enthalpy of mixing (ΔHM>0) and a symmetric miscibility gap. Paradoxically, some classical experimental studies on trace Pb2+ partitioning in barite point towards a non-ideal solid solution with ΔHM<0. In this work, we use ambient-temperature solution calorimetry and powder-XRD to clarify the non-ideal character of the anglesite–barite series. The obtained mixing model is examined in the light of existing data on the dissolution–crystallization behavior of this solid solution. Finally, the implications on the behavior of lead and radium in the environment are discussed.Our experimental data indicate that there is a significant positive enthalpy of mixing for the majority of compositions, which implies a tendency to develop a miscibility gap. However, the gap is asymmetric due to the existence of a slightly negative enthalpy of mixing in the Ba-rich miscibility range. Furthermore, there are a number of anomalies that suggest the need for a separate treatment of the Ba-rich miscibility range (PbSO4 molar fraction=XAng<∼0.14), which is in fact the most relevant from an environmental point of view. The equilibrium distribution coefficient, DPb(eq), increases dramatically in the Ba-rich side, from values less than 0.001 for XAng=0.14 to approximately 0.056 for ultra-trace concentrations of Pb. These values are significantly greater than the nearly constant value of approximately 0.0005 given by the mixing model based on natural occurrences. Even so, the preferential tendency of barium to incorporate into the solid phase precludes considering barite as a definitive host phase for lead sequestration. More interesting is the effectiveness of the anglesite–barite solid solution to incorporate radium substituting for barium and lead in the lattice positions. Although the interaction of barite with a Ra-bearing aqueous solutions leads to a significant decrease in the concentration of dissolved Ra2+, our calculations demonstrate that such a reduction is dramatically greater when the interaction occurs with stable Pb-bearing barite solids.

Preparation of SMA functionalized sulfanilic acid hydrogels and investigation of their metal ions adsorption behavior

This study is concerned with the synthesis of some network polymers and their possibility of metal ions removal from aqueous solution. A chelating hydrogel based on modified poly(styrene-alt-maleic anhydride) with p-aminobenzene sulfonic acid (sulfanilic acid) was synthesized. This hydrogel was further reacted by 1,2-diaminoethane or 1,3-diaminopropane in presence of ultrasonic irradiation for preparation of tridimensional hydrogels. The prepared hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA/DTG) techniques. Also, the swelling index of the copolymers was measured and the results clearly indicate that the uptake of the water decreased with cross-linked hydrogels with respect to noncross-linked form. Adsorption capacity of the hydrogels for the selected metal ions, i.e., Zn(II), Cu(II) and Fe(II) was investigated in detail in aqueous solutions at pH 3–7 utilizing atomic absorption spectroscopy (AAS). Also the prepared hydrogels were examined for removal of metal ions from industrial wastewater samples. This study showed that the prepared cross-linked hydrogel is very efficient in chelating the selected metal ions from aqueous solutions, compared to noncross-linked hydrogel and the affinity order was: Fe(II) > Cu(II) > Zn(II). The equilibrium distribution coefficient (k d) was determined and the findings proved that the k d value is approximately high in the case of all measured metal ions.

Effect of Temperature on Salt Diffusion into Vegetable Tissue

The diffusion process has many applications in food processing operations, such as extraction; preservation (curing, salting, and smoking); drying; and color transfer. Our main objective was to measure the diffusion coefficient, Ds, of salt into vegetable tissue (celery, mushroom, and water chestnut) as a function of temperature. For this purpose, a sample of tissue was used to separate donor and receiver compartments, each with solutions of different salt concentrations. Values of Ds were determined by periodic monitoring. The results show that the equilibrium distribution coefficient, K, and Ds of all materials were significantly affected by temperature (p < 0.05). The temperature dependence of Ds for all three materials was described by the Arrhenius equation, with water chestnut showing the lowest activation energy.

Effect of uni-univalent salts on the mass transfer of isobutyric acid between cumene and water

Effect of NaCl and KCl salts on single drop hydrodynamic and mass transfer of isobutyric acid from aqueous to cumene phases was studied. Drop size, extraction fraction and mass transfer coefficient were decreased as a consequence of isobutyrate ion adsorption which is quite obvious from interfacial tension variations. Both the used salts caused similar trends in variations; however, KCl was to some extent more efficient. These were while solute equilibrium distribution coefficient was shifted toward higher values. Using the combined mass transfer model, accompanied with a derived empirical correlation exhibited a nice agreement, with relative deviation values mostly within ±13.6%.

Sorption selectivity of cobalt(II), nickel(II), and copper(II) ions by KB-2E macroreticular carboxylic cation exchanger from aqueous-salt solutions of alkali metals

Sorption selectivity of copper(II), nickel(II), and cobalt(II) ions by KB-2E macroreticular carboxylic cation exchanger in the Na-form from dilute solutions was studied in the target concentration range (0.52.6) 103 M. The equilibrium distribution coefficients of Co2+, Ni2+, and Cu2+ were calculated. The role played by hydration of ions in their sorption by KB-2E cation exchangers is analyzed with consideration for IR spectroscopic, thermal analysis, and scanning electron microscopic data.

Continuous Crystallization of Aliskiren Hemifumarate

Active ingredients in most pharmaceutical products are complex organic molecules that require crystallization as a purification and isolation step that results in a pure product at a high process yield. Knowledge of the operating conditions required to obtain crystals with the desired crystal shape, polymorph, and morphology is critical during process development. This paper describes a two-stage mixed suspension mixed product removal (MSMPR) continuous reactive crystallization procedure developed for Aliskiren hemifumarate. This process was able to crystallize Aliskiren hemifumarate at both high purity (>99%) and high yield (>92%). A model of the crystallization was developed through the simultaneous solution of a population balance equation, kinetic expression for crystal growth and nucleation, and a mass balance. Experimental data were fit to the model to obtain kinetic parameters for crystal growth and nucleation. After including equilibrium distribution coefficient data, the model was used to optimiz...

Development of Continuous Anti-Solvent/Cooling Crystallization Process using Cascaded Mixed Suspension, Mixed Product Removal Crystallizers

This paper describes a two-stage mixed-suspension, mixed-product removal (MSMPR) continuous crystallization developed for a pharmaceutical intermediate which uses anti-solvent and cooling to generate supersaturation. The results indicate that the stage in which anti-solvent is added has a significant influence on the final crystal properties, while purity and yield were nearly identical. The population balance model was employed to determine growth and nucleation kinetics through parameter estimation. With the incorporation of measured equilibrium distribution coefficients, the model was used to optimize crystal purity and yield of the product with respect to operating temperature and residence time.

Ion Exchange Reversibility of Some Radionuclides on Zirconium Tungstosuccinate and Zirconium Tungstosalicylate at their Solid-Liquid Interfaces

Zirconium tungstosuccinate (ZWSu) and zirconium tungstosalicylate (ZWSa) composites were synthesized by anchoring moieties of succinic acid (SuA) and salicylic acid (SaA) onto zirconium tungstate (ZW), respectively. The produced exchange composites were unambiguously characterized by TGA, DTA, XRD, and FTIR spectroscopy. Thermally stable, amorphous, highly active, and multifunctional inorganic-organic exchangers were produced. The sorption behavior of the hybrid materials for removal of some hazardous radionuclides, 134Cs, 60Co, and 152+154 Eu has been studied for covering different pHs, contact time, and concentrations; capacity; 2.6, 3.14, and 4.05 meq/g were accommodated. FORM, PFORM, and PSORM equations were kinetically tested to predict the reaction mechanism. Adsorption isotherms have been constructed at different reaction temperatures (30, 40, 50, 60 ± 1°C). Adsorption of 134Cs, 60Co, and 152+154 Eu on the exchangers fit to Langmuir and Freundlich isotherms. The effect of temperature on the equilibrium distribution coefficient values was also investigated, and the thermodynamic parameters were determined; the reverse order kinetics and ion exchange reversibility were moreover indicated.

Study of ultrahigh-purity copper billets refined by vacuum melting and directional solidification

The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidification (VMDS). The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer (GDMS). The results demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%–66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu > 1.5, and they can be removed effectively under the vacuum condition of 1650–1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segregation effect in directional solidification can be remarkable when the equilibrium distribution coefficient (k0) value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.

When dissolved is not truly dissolved—The importance of colloids in studies of metal sorption on organic matter

In controlled metal sorption experiments, the equilibrium distribution coefficient is a key variable quantifying sorbate partitioning across the solid–solution interface. Separation of metals into ‘dissolved’ and ‘particulate’ fractions is commonly achieved with syringe filtration, where the boundary is somewhat arbitrarily dictated by the limited selection of available pore sizes. Investigations involving natural organic matter, such as bacterial cells or plant tissues, are especially prone to experimental artifacts if the substrate releases abundant colloidal compounds that contribute to sorption by binding free metal cations in a pH-dependent fashion yet pass through conventional filters, causing the truly dissolved fraction to be grossly overestimated.We observed this phenomenon during a study of lanthanide sorption on a marine macroalga, Ulva lactuca, as a function of pH. At low ionic strength, distribution coefficients calculated for a 0.22-μm size cutoff falsely imply that metal sorption reverses to gradual release above pH 4.6, instead of continuing to increase. Centrifuging the filtrates in Amicon® Ultra units (30 and 3kDa molecular weight cutoff) revealed a mounting proportion of colloid-bound metal, constituting up to 95% of the ‘dissolved’ (<0.22μm) fraction near pH 8. Measurements of DOC concentrations suggest this being due to pH-dependent binding of free metal cations to a fixed pool of organic colloids. The process is well described with a simple 2-site Langmuir isotherm in 0.05, 0.5, and 5.0M NaCl. Using this model to correct the original distribution coefficients not only removed the spurious reversal at low ionic strength, but also uncovered a prominent suppressive effect on the intermediate and high ionic strength data that had initially gone undetected. Ultra-filtration may thus be an essential analytical tool for proper characterization and interpretation of metal sorption on organic matter over a wide range of experimental conditions. Some implications are discussed for the use of biosorbents in the remediation of metal-contaminated waste waters.

Determination of Equilibrium Distribution Coefficients of Impurities in Phosphorus by Vertical Zone-melting Technique

The equilibrium distribution coefficients of 12 impurities (As, Fe, Ca, Co, Al, Cr, Cu, Mg, Mn, Ni, Pb, Zn) in phosphorus were obtained by measuring their effective distribution coefficients at zone travel rate of 3, 5, 10, 15, and 20 mm·h −1 in the purification process with vertical zone-melting technique. The results indicate that the method is reliable. The equilibrium distribution coefficients are below 0.3 except arsenic.

Redox-Responsive Gels with Tunable Hydrophobicity for Controlled Solubilization and Release of Organics

The hydrophobicity of the chemical environment within a redox-responsive polymer gel synthesized by copolymerization of hydroxybutyl methacrylate (HBMA) and vinylferrocene (VF) can be controlled by tuning the oxidation state of the redox-responsive moiety, ferrocene. When ferrocene is in the uncharged reduced state, the gel is hydrophobic and selectively extracts butanol from aqueous solution. Upon oxidation to ferricenium ions, charge is induced at the ferrocene sites making the gel hydrophilic, with a reduced capacity for butanol relative to water. Equilibrium distribution coefficients and separation factors provide quantitative evidence for this changing preference for butanol depending on oxidation state. The selection of the monomer constituting the polymer backbone, HBMA, was based on an initial screening using the Hansen solubility parameters of commercially available monomers. The effect of the various constituents of the gel on the gel's butanol extraction ability has been ascertained experimentally.