Investigations on the Reactive Extraction of Glyoxylic Acid by Amberlite-LA2 Dissolved in Alcoholic Diluents

In this study, reactive extraction of glyoxylic acid (0.93 kmol·m^?3) using Amberlite-LA2 (0.24 to 1.67 kmol·m^?3) in five different alcoholic diluents is performed at 298 K. The extraction ability of Amberlite-LA2 is found to be in the order of isoamylalcohol (IAA) > nonan-1-ol > octan-1-ol > decan-1-ol > dodecanol. Maximum extraction efficiency, 98.92% is obtained at 1.67 kmol·m^?3 of Amberlite-LA2 in IAA. The values of stoichiometric coefficient (m), overall equilibrium constant (K_E) and individual constants (K₁₁, K₂₁, and K₁₂) are estimated. The effect of diluent on K_D is also quantified by applying LSER model using solvatochromic parameters of diluents.     

Effect of Temperature on Kinetics and Adsorption Profile of Endothermic Chemisorption Process: –Tm(III)–PAN Loaded PUF System

Abstract

The sorption behavior of 3.18×10^?6 mol l^?1 solution of Tm(III) metal ions onto 7.25 mg l^?1 of 1‐(2‐pyridylazo)‐2‐naphthol (PAN) loaded polyurethane foam (PUF) has been investigated at different temperatures i.e. 303 K, 313 K, and 323 K. The maximum equilibration time of sorption was 30 minutes from pH 7.5 buffer solution at all temperatures. The various rate parameters of adsorption process have been investigated. The diffusional activation energy (ΔE_ads) and activation entropy (ΔS_ads) of the system were found to be 22.1±2.6 kJ mol^?1 and 52.7±6.2 J mol^?1 K^?1, respectively. The thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) were calculated and interpreted. The positive value of ΔH and negative value of ΔG indicate that sorption is endothermic and spontaneous in nature, respectively. The adsorption isotherms such as Freundlich, Langmuir, and Dubinin–Radushkevich isotherm were tested experimentally at different temperatures. The changes in adsorption isotherm constants were discussed. The binding energy constant (b) of Langmuir isotherm increases with temperature. The differential heat of adsorption (ΔH_diff), entropy of adsorption (ΔS_diff) and adsorption free energy (ΔG_ads) at 313 K were determined and found to be 38±2 kJ mol^?1, 249±3 J mol^?1 K^?1 and –40.1±1.1 kJ mol^?1, respectively. The stability of sorbed complex and mechanism involved in adsorption process has been discussed using different thermodynamic parameters and sorption free energy.     

Comparative Study on Reactive Extraction of Picolinic Acid with Six Different Extractants (Phosphoric and Aminic) in Two Different Diluents (Benzene and Decan-1-ol)

The equilibrium study on reactive extraction of picolinic acid by six different extractants (phosphoric and aminic) dissolved in two different diluents (benzene and decane-1-ol) is carried out to evaluate the performance of extractants and diluents. The extraction ability in terms of the distribution coefficient (K _D) is found to be in the order of tri-n-octylamine (TOA) ≥ tri-n-dodecylamine (TDDA) > di-2-ehylhexyl phosphoric acid (D2EHPA) > tri-n-butyl phosphate (TBP) > tri-octyl methyl ammonium chloride (Aliquat 336) > tri-n-octyl phosphine oxide (TOPO) with both diluents. Decan-1-ol is found to be the better solvating medium for the acid-extractant complexes. A mathematical model based on mass action law is employed to estimate the values of partition coefficient (P) and dimerization constant (D) in physical extraction, and equilibrium extraction constants (K _E) in chemical extraction. The values of loading ratios (Z) less than 0.5 imply the formation of (1:1) acid:extractant solvates in the organic phase. Decan-1-ol with TOA is the most effective solvation medium with K _{D, max} = 9 at 0.01 kmol · m^?3 of picolinic acid and K _E = 19.448 m³ · kmol^?1.     

Adsorption Thermodynamic and Kinetic Studies of Fluoride Aqueous Solution Treated with Waste Iron Oxide

This study uses a waste iron oxide material (BT3), which is a by-product of the fluidized-bed Fenton reaction (FBR–Fenton), for the treatment of a fluoride (F^?) solution. The purpose of this study is to investigate a low-cost sorbent as a replacement for the current costly methods of removing fluoride from wastewater. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) are used to characterize the BT3. Contact time, F^? concentration (from 0.75 to 6 mmol L^?1), and temperature (from 303 to 323 K) are used as operation parameters to treat the fluoride. The highest F^? adsorption capacity of the BT3 adsorbent was determined to be 1.17 mmol g^?1 (22.2 mg g^?1) for a 6 mmol L^?1 initial F^? concentration at pH 3.9 ± 0.2 and 303 ± 1 K. Adsorption data were well described by the Langmuir model, and the thermodynamic constants of the adsorption process, ΔG°, ΔH°, and ΔS°, were evaluated as ?1.63 kJ mol^?1 (at 303 K), ?1.75 kJ mol^?1, and ?52.4 J mol^?1 K^?1, respectively. Additionally, a pseudo-second-order rate model was adopted to describe the kinetics of adsorption. BT3 could be regenerated with NaOH, and the regeneration efficiency reached 95.1% when the concentration of NaOH was 0.05 mol L^?1.     

Mixed Matrix Silicone and Fluorosilicone/Zeolite 4A Membranes for Ethanol Dehydration by Pervaporation

The ability of homogeneous and mixed matrix membranes prepared using standard silicone rubber, poly(dimethylsiloxane) (PDMS), and fluorosilicone rubber, poly(trifluoropropylmethylsiloxane) (PTFPMS), to dehydrate ethanol by pervaporation was evaluated. Although PDMS is generally considered to be the benchmark hydrophobic membrane material in pervaporation, water/ethanol molar permselectivity of a pure PDMS membrane was found to be 0.89 for a feed containing 80/20 w/w ethanol/water at 50°C, indicating a slight selectivity for water. Fluorinated groups in PTFPMS improved the water-ethanol permselectivity to 1.85, but decreased the water permeability from 9.7 × 10^?12 kmol · m/m² · s · kPa in PDMS to 5.1 × 10^?12 kmol · m/m² · s · kPa (29,000 and 15,200 Barrer, respectively). These water permeabilities are attractive, particularly since the rubbery materials should not experience the steep declines in water permeability observed with most standard dehydration membranes as water concentration in the feed decreases. However, the water selectivity is lower than desired for most applications. Particles of hydrophilic zeolite 4A were loaded into both PDMS and PTFPMS matrices in an effort to boost water selectivity and further improve water permeability. Water-ethanol permselectivities as high as 11.5 and water permeabilities as high as 23.2 × 10^?12 kmol · m/m² · s · kPa were observed for the PTFPMS/zeolite 4A mixed matrix membranes?6 times higher than for the unfilled PTFPMS membrane.     

Separation of Electrochemically Generated Ce(IV) from Rare Earths(III) in Nitric Acid Media by TBP Impregnated Resin

Abstract

Electro‐oxidation of Ce(III) to Ce(IV) in nitric acid media at different anode materials with high oxygen evolution overpotential was carried out. Ce(IV) nitrato complexes were adsorbed on a novel resin, based on porous silica beads with immobilized polystyrene/DVB copolymer, that was impregnated with tri‐n‐butyl phosphate (TBP). Under the studied conditions, Ce(IV) sorption increased with increasing nitric acid concentration (0.5–6 mol · dm^?3). Oxidation of sorbent by adsorbed Ce(IV) species resulting in Ce(III) release to the solution was observed and thoroughly evaluated. In spite of problems with TBP leakage (12%), column separation of pure Ce(IV) from Y(III) and La(III) was achieved in 6 mol · dm^?3 HNO₃ at 288 K. Ce(IV) breakthrough capacity was 0.48 mol · kg^?1‐TBP. Column regeneration with 0.1 mol · dm^?3 nitric acid yielded Ce solution with purity higher than 99.99 wt.% with respect to La and Y impurities.     

SINGLE-LAYER DRYING BEHAVIOR OF MEXICAN TEA LEAVES (CHENOPODIUM AMBROSIOIDES) IN A CONVECTIVE SOLAR DRYER AND MATHEMATICAL MODELING

Single-layer solar drying experiments were conducted for Mexican tea leaves (Chenopodium ambrosioides) grown in Marrakech. An indirect forced convection solar dryer was used in drying the Mexican tea leaves at different conditions such as ambient air temperature (21° to 35°C), drying air temperature (45° to 60°C) with relative humidity (29 to 53%), airflow rate (0.0277 to 0.0556 m ³/s), and solar radiation (150–920 W/m²). The experimental drying curves showed only a falling rate period. In order to select the suitable form of drying curves, 14 mathematical models were applied to the experimental data and compared according to their statistical parameters. The main factor in controlling the drying rate was found to be the temperature. The drying rate equation was determined empirically from the characteristic drying curve. The diffusion coefficient of the Chenopodium ambrosioides leaves was estimated and varied between 1.0209 × 10^?9 and 1.0440 × 10^?8 m ²·s^?1.The activation energy was found to be 89.1486 kJ·mol^?1.     

Extraction of zinc from ammoniacal/ammonium sulphate solutions by LIX 54

The extraction of zinc from ammoniacal/ammonium sulphate aqueous media using LIX 54 has been studied. The metal extraction rate has been examined and also the effect of temperature on the extraction of zinc (ΔH° = −8·8 kJ mol⁻¹). The effect of the aqueous pH, and therefore zinc ammine complex formation, on the extraction of zinc was studied. Stripping of the metal from loaded organic phases was carried out at various rates, temperatures (ΔH° = 3·2 kJ mol⁻¹) and sulphuric acid concentrations. The results obtained were compared with others obtained from the literature wherein different extractants were used. © 1998 SCI.     

Solvent extraction and separation of rare earths from chloride media using α-aminophosphonic acid extractant HEHAMP

Solvent extraction and separation of rare earths (REs: La ~ Lu, plus Y and Sc) by a novel synthesized extractant, (2-ethylhexylamino)methyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, abbreviated as H₂A₂), were investigated in chloride medium. The favorable separation factors (SFs) between adjacent heavy REs suggested that HEHAMP has a better separation performance than P507. The extracted complex of trivalent REs was determined to be REClH₂A₄ by the slope analysis method. Thermodynamic parameters (ΔH, ΔG, and ΔS) of Lu were calculated as 7.47 kJ mol^?1, ?6.05 kJ mol^?1, and 45.4 J mol^?1 K^?1 at 298.15 K, respectively, which indicate that the extraction reaction of Lu is an endothermic process. The loading capacity of 30% (v/v) HEHAMP toward Lu(III), Yb(III), and Y(III) was about 15.17 g Lu₂O₃/L, 14.46 g Yb₂O₃/L, and 12.64 g Y₂O₃/L, respectively. HCl is the most efficient stripping acid, and 92% of the loaded Yb(III) can be stripped by one-stage stripping with 2 mol/L HCl.     

Coupled Transport of Zr(IV) through Tri-n-butylphosphate-Xylene-Based Supported Liquid Membranes

Abstract

The transport of Zr(IV) through tri-n-butylphosphate-xylene-based liquid membranes, supported in a polypropylene hydrophobic microporous film, has been studied. The concentration of HNO₃ in the feed solution and tri-n-butylphosphate (TBP) carrier in the membrane were varied, and the flux and permeability coefficients were determined. The optimum conditions found for maximum flux were determined to be 10 mol/dm³ HNO₃ and 2.93 mol/dm³ TBP with a flux value of 12.9 × 10^?6 mol · m^?2 · s^?1. The solvent extraction study revealed that 1.25 to 3.5 protons are involved in zirconium transport, and that two molecules of TBP are involved in the complex formation. The value of protons involved varies with acid concentration. The zirconium ion transport is coupled with nitrate ions transport.     

Efficacy of tri-n-octylamine,tri-n-butyl phosphate and di-(2-ethylhexyl) phosphoric acid for reactive separation of protocatechuic acid

ABSTRACT

Owing to its chemical and pharmacological significances, the efficacy of reactive separation of protocatechuic acid (0.001–0.01 kmol m^?3) from aqueous stream by means of tri-n-octylamine (TOA), di-2-ethylhexyl phosphoric acid (D2EHPA) as well as tri-n-butyl phosphate (TBP) in octanol has been investigated, in terms of extraction efficiency, loading ratio, equilibrium complexation constants, and distribution coefficients. Extraction ability was obtained in the order TOA (91.2%) > TBP (88.64%) > D2EHPA (86.43%). In all cases, 1:1 protocatechuic acid:extractant complex is obtained. Further, diffusion coefficients, number of stages for extraction systems, and relative basicity model were used for relating the efficacy.     

Extraction relationship of Li+ and H+ using tributyl phosphate in the presence of Fe(III)

ABSTRACT

During the extraction of lithium from high Mg-containing salt lake brines by tributyl phosphate (TBP) in the presence of Fe(III), H⁺ is used to stabilize Fe(III). However, the distribution ratio of H⁺ (D_H) is 4–6 times higher than that of Li⁺ (D_Li), which affects the extraction of Li⁺ significantly. In this study, the competition mechanism between H⁺ and Li⁺ was investigated by spectral analysis and thermodynamic equilibrium. The extracted species are determined as HFeCl₄ · 2TBP and LiFeCl₄ · 2TBP for H⁺ and Li⁺, respectively. The apparent equilibrium constants are K_H = 799.8 and K_Li = 120.6, respectively. Both equilibrium constants and the distribution ratios for H⁺ and Li⁺ extraction show that extraction of H⁺ is stronger than Li⁺.     

Characterization of the Binding Interaction between Poly(Epicholorohydrin‐Diamine) and Reactive Dyes using a Multiple Linear Regression and Quartz Crystal Microbalance Methods

Abstract

The binding processes of Reactive Red K‐2BP (K‐2BP) and Reactive Violet K‐3R (K‐3R) onto poly(epicholorohydrin‐diamine)(PEPIDA) in solution and film were investigated by spectrophotometric and quartz crystal microbalance (QCM) methods, respectively. By using a multiple linear regression technique, the concentrations of the colored components in the mixtures of dye+PEPIDA were measured simultaneously from the absorbance spectra. The binding equilibrium constants for K‐3R and K‐2BP onto PEPIDA in solution were estimated to be 9.31×10⁶ and 1.86×10⁶ L · mol^?1, respectively. The difference in the color removal between K‐3R and K‐2BP by PEPIDA was discussed. The binding processes of K‐3R and K‐2BP onto PEPIDA film were followed by the QCM. The binding equilibrium constants were evaluated to be 1.27×10⁶ and 3.28 ×10⁵ L · mol^?1 for K‐3R and K‐2BP onto PEPIDA film, respectively. They are less than those determined in PEPIDA solutions. The binding rate constants for K‐3R and K‐2BP onto PEPIDA film were estimated to be 1.43×10⁵ and 1.72×10⁵ L · mol^?1 · s^?1, respectively.     

Equilibria and Kinetics of Extraction of Citric Acid from Aqueous Solutions in Alamine 336–Cyclohexanone System

Abstract

Equilibria and kinetics for the extraction of citric acid by Alamine 336 in cyclohexanone as diluent are reported. The theory of extraction accompanied by a chemical reaction has been used to obtain the intrinsic kinetics of extraction of citric acid by Alamine 336 in cyclohexanone. The reaction has been found to be first order in both Alamine 336 and citric acid with a rate constant of 8.8×10^?3 m³ kmol^?1 s^?1.     

Kinetics of Silver Extraction with Triisobutylphosphine Sulfide

Abstract

Kinetics of silver extraction from nitrate solutions with triisobutylphosphine sulfide dissolved in n-octane was studied. Experiments were carried out in a rotating diffusion cell. The rate constants of forward and reverse chemical reactions were evaluated: the former k^? _f = 1.064 × 10^?3 m⁹/(mol³·s) and the latter k^? _f = 2.085 × 10^?1 s^?1. The value obtained for the activation energy shows that the process of silver extraction with triisobutylphosphine sulfide is a predominantly diffusion-controlled process.     

Reactive extraction of itaconic acid using tri‐n‐butyl phosphate and aliquat 336 in sunflower oil as a non‐toxic diluent

Itaconic acid finds a place in various industrial applications. It can be produced by biocultivation in a clean and environment friendly route but recovery of the acid from the dilute stream of the bioreactor is an economic problem. Reactive extraction is a promising method to recover carboxylic acid but suffers from toxicity problems of the diluent and extractant employed. So there is need for a non‐toxic extractant and diluent or a combination of less toxic extractants in a non‐toxic diluent that can recover acid efficiently. Effect of different extractants: tri‐n‐butylphosphate (TBP) (an organophosporous compound) and Aliquat 336 (a quaternary amine) in sunflower oil was studied to find the best extractant–sunflower oil combination. Equilibrium complexation constant, K_E, values of 1.789 and 2.385 m³ kmol^?1, respectively, were obtained for itaconic acid extraction using TBP and Aliquat 336 in sunflower oil. The problem of toxicity in reactive extraction can be reduced by using a natural non‐toxic diluent (sunflower oil) with the extractant. Copyright © 2010 Society of Chemical Industry     

Control of urethane prepolymerization from reaction kinetics and viscosity

A theory of the kinetics of consective second-order reactions has been generalized and used to interpret observations of toluene-2,4-diisocyanate reacting with polyoxypropylene glycol without diluent or catalyst to form a urethane prepolymer. The first reaction in the sequence has a second-order rate constant of 1.2 × 10^?7 m³mole^?1 sec^?1 at 303°K with an activation energy of 3.5 × 10⁴ J mole^?1. The rate constant of the second reaction appears to be one half of this. Deviations from the theoretical kinetics and an increase in the viscosity of the prepolymer product above 1.9 kg m^?1s^?1 (measured at 313°K) when the temperature of reaction exceeds about 360°K show that above this temperature, undesirable side reactions are important.     

Kinetics of thermal inactivation of transglutaminase from a newly isolated Bacillus circulans BL32

BACKGROUND: This paper describes the modeling of the kinetics of thermal inactivation of transglutaminase (TGase) from a newly isolated Bacillus circulans BL32, isolated from the Amazon environment. The purified enzyme was incubated at temperatures ranging from 30 to 70 °C and values of the thermodynamic inactivation parameters, such as activation energy (ΔE), activation enthalpy (ΔH), activation entropy (ΔS), and free energy (ΔG) for thermal inactivation, were calculated. RESULTS: The kinetics of TGase thermo‐inactivation followed a Lumry–Eyring model. The enzyme was very stable up to 50 °C, with approximately 50% of activity remaining after heating for 12 h. It was completely inactivated by incubation at 70 °C for 2 min. ΔE for TGase was 350.5 kJ mol^?1. ΔH and ΔS for thermo‐inactivation of the TGase were 347.8 kJ mol^?1 and 744 J mol^?1 K^?1 at 50 °C, respectively. Dynamic light scattering measurements suggest that the thermal inactivation of this microbial TGase can be partially attributed to the formation of aggregates. CONCLUSION: These results provide useful information about the thermal characteristics of the microbial TGase from B. circulans BL32 and indicate that this enzyme could be a good candidate for industrial applications. Copyright © 2009 Society of Chemical Industry     

Modeling the Dehydration of Apple Slices by Deep Fat Frying

One of the objectives of immersion frying is to remove water from the food. Thus, predicting moisture loss is important when developing a model for that process. With the aim to model moisture transfer during apple frying, Granny Smith apple slabs were processed at 140, 150, 160, and 170°C. The moisture diffusivity was computed, ranging between 10.7 · 10^?9 and 17.7 · 10^?9 m² · s^?1. There was a close fit between the model and the experimental data (average %var 99.0). Model validation was carried out considering different slice thickness. Temperature influence was interpreted by the Arrhenius relationship with an activation energy of 25.4 kJ · mol^?1.     

Extraction of aconitic acid from mixtures of organic acids and cane molasses solutions using supported liquid membranes

This paper details experimental trials of aconitic acid transport from defined mixtures of organic acids (trans‐aconitic, oxalic, malic and citric) and from cane molasses solutions using a supported liquid membrane (SLM) apparatus. The SLM was impregnated with tributyl phosphate extractant combined with Shellsol 2046 diluent. The transport rates of the organic acids, bulk impurities and glucose were measured. The conditions varied were: extractant to diluent ratio (1:3–3:1), organic acid concentration (2.5–40 mg cm^?3 organic acid), pH of departure phase (1–5.5) and temperature (22–80 °C). Results for the organic acid mixtures showed that aconitic acid and oxalic acid were transported at much greater rates than malic and citric acids. Aconitic acid was transported to a significant degree with recovery of 400 g kg^?1 over a 24 h period. Operation at temperatures higher than 22 °C caused instability of the membrane and bulk leakage across the membrane. With molasses, the purity of the aconitic acid recovered ranged between 400 and 600 g kg^?1 (dry basis) with aconitic acid transport rates of 0.17–0.25 g m^?2 min^?1. The extraction of other acids (oxalic, malic and citric) and impurities was significantly less, hence a process to produce high purity aconitic acid based on this method is technically feasible. © 2002 Society of Chemical Industry