Continuous Cloud Point Extraction of Volatile Organic Contaminants from Wastewater in a Multi-Stage Rotating Disc Contactor: Effect of Structure and Concentration of Solutes

Abstract

Cloud point extraction (CPE) has been successfully scaled up to continuously remove aromatic contaminants from wastewater in a multi-stage rotating disc contactor (RDC) using t-octylphenolpolyethoxylate. The extraction performances for the removal of organic solutes with different structures and degrees of hydrophobicity were compared here for both batch and continuous CPE. Included are the volatile aromatics benzene, toluene, and ethylbenzene; volatile chlorinated compounds dichloroethane, trichloroethylene, and tetrachloroethylene; and non-volatile phenolics phenol, o-cresol, and catechol. The higher the K_ow (octanol-water partition coefficient) or hydrophobicity of the solutes, the better the extraction due to the greater affinity of solutes to solubilize into micelles. The empirical linear correlations between log K_ow, log (solute partition ratio), and log (height of transfer unit or HTU) were developed. Toluene is used as a model solute for the study of effect of initial solute concentrations in the continuous RDC. The extraction ability decreases as the concentration of toluene in the wastewater increases mainly due to coacervate entrainment into the overhead effluent.     

Can Kosmotropic Salt/Chaotropic Ionic Liquid (Salt/Salt Aqueous Biphasic Systems) be Used to Remove Pertechnetate From Complex Salt Waste?

Abstract

Aqueous solutions of water‐structuring, kosmotropic salts (e.g., salts of PO₄ ^3?, HPO₄ ^2?, CO₃ ^2?) will salt‐out water‐destructuring chaotropic ionic liquids (ILs) (e.g., 1‐butyl‐3‐methylimidazolium chloride, ([C₄mim]Cl)) forming salt/salt aqueous biphasic systems (ABS). The chaotropic pertechnetate (TcO₄ ^?) anion will partition without the use of an extractant into the IL‐rich phase. These complex salt/salt ABS are not unlike the complex and salt‐rich Hanford tank waste, and thus have been used here as a simple model to show effectiveness in the partitioning of TcO₄ ^? from such tank waste into an IL‐rich phase.     

Partitioning behaviour of cephalexin and 7‐aminodeacetoxicephalosporanic acid in PEG/ammonium sulfate aqueous two‐phase systems

In order to develop an aqueous two‐phase system (ATPS) for cephalexin synthesis with extractive bioconversion, the partitioning behaviour of cephalexin and 7‐aminodeacetoxicephalosporanic acid (7‐ADCA) in poly(ethylene glycol) (PEG)/salt ATPS were examined. Parameters such as PEG size, salt type and tie line length were investigated to find a primary extraction system. In PEG400/ammonium sulfate and PEG400/magnesium sulfate systems, the partition coefficient of cephalexin (K_C) was larger than 1 while that of 7‐ADCA (K_A) deviated about 1.5. Addition of neutral salts, surfactants and water‐miscible solvents were also investigated in the primary ATPS in order to improve the separation efficiency. K_C greatly increased when neutral salts and surfactants were added to the PEG400/ammonium sulfate primary systems whereas K_A was only slightly higher than that of the additive‐free ATPS. In an improved ATPS for extractive bioconversion, consisting of PEG400 (20% w/w), ammonium sulfate (17.5% w/w), methanol (5% w/w) and NaCl (3% w/w), a K_C value of up to 15.2 was achieved; K_A was 1.8; K_P (partition coefficient of phenylglycine methyl ester) was 1.2 and the recovery yield of cephalexin was 94.2%. The results obtained from the extractive bioconversion of cephalexin in the improved ATPS showed that it is feasible to perform such an enzymatic process in an ATPS and the system offers the potential as a model for enzymatic synthesis of some water soluble products. © 2001 Society of Chemical Industry     

Applications of choline amino acid ionic liquid in extraction and separation of flavonoids and pectin from ponkan peels

Choline leucine ionic liquid solution was chosen to simultaneously extract flavonoids and pectin from ponkan peels, which were subsequently isolated by the corresponding K₃PO₄-based aqueous biphasic systems (ABS). Under optimized conditions of 54% solution for 100 min extraction at liquid–solid ratio 17, the predicted yields of flavonoids and pectin achieved 1.33% and 13.42%, respectively, the flavonoids determined directly after extraction and the pectin after ABS purification, with the two corresponding measured yields of 1.26% ± 0.04% and 12.85% ± 0.51%. Under optimal extraction, crude flavonoids contained maximal total flavonoid content of about 20% ± 1% after purification of the ABS involving 25% K₃PO₄ and dilution precipitation. What was directly isolated from K₃PO₄-rich phase was presumed to be a modified pectin.     

Enrichment of Aromatic Compounds Using Ionic Liquid and Ionic Liquid-Based Aqueous Biphasic Systems

Both hydrophibic [C₈mim][PF₆] and [C₄mim]Cl/(K₂CO₃, K₂HPO₄ or K₃PO₄) aqueous biphasic system (ABS) were employed for the enrichment of aromatic compounds including nitrobenzene, 4-nitrophenol, phenol and aniline from aqueous solutions. In [C₈mim][PF₆] enrichment system, the distribution ratio (D) of nitrobenzene and aniline increase with the increasing of pH values of aqueous phase from 2 to 8, but there is no obvious change for 4-nitrophenol and phenol. And the D values of the aromatic compounds decrease with the phase ratio change from 1/5 to 1/30 (IL phase volume/aqueous phase volume). In [C₄mim]Cl/(K₂CO₃, K₂HPO₄ or K₃PO₄), the distribution ratio increase with the increasing of the salts concentrations. The distribution ratio order in [C₈mim][PF₆] and [C₄mim]Cl/kosmotropic salt ABS is nitrobenzene > phenol > aniline > 4-nitrophenol. It is expected that these results are promising for the removal of the aromatic compounds from water, especially for sample enrichment in analytical science.     

Permselectivities of some aromatic compounds in organic medium through cellulose acetate membranes by reverse osmosis

Reverse osmosis of some aromatic compounds in 1-propanol solution using porous cellulose acetate membranes and some factors which influence the organic solute permeability were investigated. Reverse osmosis data for a number of benzene derivatives showed that only phenol was rejected and the others were enriched. For the compounds with various substituent groups, the solute permeabilities have the following order; OH < CH₃ < H < Cl < NH₂ < NO₂. In the series of benzene, naphthalene, and anthracene, the permeability is related to the molar volume of solutes and varied as follows: benzene < naphthalene < anthracene. Generally speaking, there are two factors—a partition coefficient and a diffusion coefficient—for governing the permeation behavior through the membrane. Under the condition that no steric effect is exerted, the partition coefficient exclusively is a dominant factor. A good correlation between the partition coefficient of a particle and that of the membrane was pound. The partition coefficients are closely related to the dipole moment of solutes.     

SELECTIVE AND QUANTITATIVE PARTITIONING OF PERTECHNETATE IN POLYETHYLENE-GLYCOL BASED AQUEOUS BIPHASIC SYSTEMS

ABSTRACT

The partitioning behavior of technetium has been investigated in polyethylene glycol (PEG)-based aqueous biphasic systems using K₃P0₄, K₂C0₃, Na₃(citrate), (NH₄) ₃(citrate), (NH₄) ₂S0₄, and NaOH as biphase-forming salts, and PEGs with average molecular weights of 1500, 2000, 3400, and 6000. Pertechnetate quantitatively partitions to the PEG-rich phase in these systems. The distribution ratios increase with increasing salt or PEG concentration used to form the aqueous biphasic systems, consistent with the increasing phase incompatibility. At a given concentration of salt and PEG, D_Tc values in the various systems increase in the order NaOH < (NH₄) ₂S0₄ < (NH₄)3(citrate) < K₂C0₃ < K₃P0₄ and PEG-1500 < PEG-2000 < PEG-3400 < PEG-6000. The distribution ratios are lower at very high or very low pH values than they are in the 3-9 pH range. Matrix ions may also influence the D_Tcvalues by affecting the aqueous biphasic system composition. Technetium can be stripped from the loaded PEG-rich phase by contact with a clean salt solution containing SnCl₂, which reduces TcO₄ to an oxy-chloro cationic species that partitions to the salt-rich phase.     

Pesticide Removal from Aqueous Solutions by Adding Salting Out Agents

Phase segregation in aqueous biphasic systems (ABS) composed of four hydrophilic ionic liquids (ILs): 1-butyl-3-methylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium methylsulfate (C_nC₁im C₁SO₄, n = 2 and 4), tributylmethyl phosphonium methylsulfate (P₄₄₄₁ C₁SO₄) and methylpyridinium methylsulfate (C₁Py C₁SO₄) and two high charge density potassium inorganic salts (K₂CO₃ and K₂HPO₄) were determined by the cloud point method at 298.15 K. The influence of the addition of the selected inorganic salts to aqueous mixtures of ILs was discussed in the light of the Hofmeister series and in terms of molar Gibbs free energy of hydration. The effect of the alkyl chain length of the cation on the methylsulfate-based ILs has been investigated. All the solubility data were satisfactorily correlated to several empirical equations. A pesticide (pentachlorophenol, PCP) extraction process based on the inorganic salt providing a greater salting out effect was tackled. The viability of the proposed process was analyzed in terms of partition coefficients and extraction efficiencies.     

Partitioning of Charged Solutes in Poly(Ethylene Glycol)/Potassium Phosphate Aqueous Two-Phase Systems

Abstract

A mathematical model based on the dissociation of charged compounds and the pH of each phase is developed to describe the partitioning of charged compounds in aqueous two-phase systems. Observed partition coefficients of several charged and uncharged compounds, including three pairs of oppositely charged analogs (tryptamine/indole 3-acetic acid, 5-methoxytryptamine/5-methoxyindole 3-acetic acid and 2-(p-tolyl) ethylamine/p-tolyl acetic acid), are compared in identical poly-(ethylene glycol)/potassium phosphate aqueous two-phase systems over the pH range of 5.5 to 9.2. Among these pairs, the partition coefficients of the acids increased with increasing pH, from 8.4 to 33.3 for indole 3-acetic acid, from 11.4 to 53.9 for 5-methoxyindole 3-acetic acid, and from 4.2 to 17.7 for p-tolyl acetic acid. The amine partition coefficients also increased with increasing pH, from 4.0 to 7.8 for tryptamine, from 5.8 to 12.2 for 5-methoxytryptamine, and from 1.6 to 3.0 for 2-(p-tolyl) ethylamine, respectively. Consistent with the derived model, the greatest rate of increase in the partition coefficients of the acids occurs at low pH, while the greatest rate of increase in amine partition coefficients occurs at high pH. The ratio of partition coefficients for these pairs predicted by the model agrees with the observed partition ratio. The results indicate that charge, in addition to hydrophobic effects previously described, plays a major role in the partitioning of biological compounds.     

Determination of K ow of Substituted Polycyclic Aromatic Compounds

Octanol-water partition coefficients (K _ow s) of substituted polycyclic aromatic compounds (PACs), anthracene-, pyrene- and quinoline-derivatives, have been determined using HPLC. The determined K _ow s have been compared with results from theoretical fragment methods, developed by Rekker and Mannhold [1] and by Hansch and Leo [2]. The results showed that if these theoretical methods are to be useful with simple substituted PAHs they must be applied differently than normally supposed, due to intramolecular steric conditions. Comparison of the determined K _ow s with measured K _oc values showed that the relationship between K _oc and K _ow is not straightforward, and that prediction of K _oc from K _ow alone will not give results applicable for substituted polycyclic aromatic compounds.     

Betacyanins extraction from Hylocereus polyrhizus using alcohol/salt-based liquid biphasic partitioning system and antioxidant activity evaluation

Betacyanins have gained increasing interest as natural food dye because of their health-promoting effects. This study investigated the betacyanins extraction from peel and flesh of red–purple pitaya using ethanol/K₂HPO₄-based liquid biphasic partitioning system (LBPS) by optimised concentrations of ethanol, K₂HPO₄, NaCl and crude. Overall, the highest values of betacyanins concentration in alcohol-rich top phase (C_t), phase volume ratio (V_r) and partition coefficient (K) of betacyanins that represented an optimum betacyanins extraction from the peel (98.080%, 1.667 and 51.097, respectively) and flesh (96.256%, 2.167 and 25.764, respectively) were achieved. Lastly, conventional solvent extractions, colour characterisation and antioxidant activity evaluation were conducted.     

Dye-Affinity Partitioning of Acidic,Basic, and Neutral Proteins in Ionic Liquid-Based Aqueous Biphasic Systems

The partitioning behavior of model acidic (bovine serum albumin, BSA), basic (hen egg white lysozyme, LYS), and neutral (horse heart myoglobin, MYO) proteins in ionic liquid-based aqueous biphasic systems containing Reactive Red-120 dye has been reported. This study found that partition coefficients of the proteins depended on their chemical structures, pH of the aqueous phase, temperature, and composition of the aqueous biphasic system. It was found that partition coefficients of proteins in aqueous biphasic system containing RR-120 were in the order of LYS > MYO > BSA. Recovery of the hydrophilic ionic liquid, [C₄mim]Br, was achieved by using hydrophobic ionic liquid, [C₄mim]PF_6.     

Extraction of erythromycin‐A using colloidal liquid aphrons: I. Equilibrium partitioning

Colloidal liquid aphrons (CLAs) are surfactant‐stabilised solvent droplets which have recently been explored for use in pre‐dispersed solvent extraction (PDSE). In this work, the equilibrium partitioning of a microbial secondary metabolite, erythromycin, has been studied using both CLAs (formulated from 1% (w/v) Softanol 120 in decanol and 0.5% (w/v) SDS in water) and surfactant‐containing, two‐phase systems. The equilibrium partitioning of erythromycin was found to be strongly influenced by the extraction pH, and exhibited a marked change either side of the pK_a of the molecule. A modified form of the Henderson–Hasselbach equation could be used as a simple design equation to predict the equilibrium partition coefficient (m_eryt = C_org /C_aq) as a function of pH. For extraction experiments with dispersed CLAs where pH > pK_a, m_eryt values as high as 150 could be obtained and the erythromycin could be concentrated by factors of up to 100. Experiments were also carried out in surfactant‐containing, two‐phase systems to determine the effect of individual surfactants used for aphron formulation on erythromycin partitioning. For extraction at pH 10 neither the Softanol (a non‐ionic surfactant) nor SDS (an anionic surfactant) had any influence on the equilibrium erythromycin partition coefficients. For stripping at pH 7, however, it was found that recovery of erythromycin from the organic phase decreased with increasing concentration of SDS, although again the Softanol had no influence on the equilibrium. The effect of SDS was attributed to a specific electrostatic interaction between individual erythromycin and SDS molecules under stripping conditions. The m_eryt values and concentration factors achievable in the two‐phase systems were considerably less than those for the PDSE experiments. The physical properties of the two‐phase systems, ie density, viscosity, interfacial tension, etc, and the equilibrium distribution of the surfactants were also determined in relation to subsequent studies on the kinetics of erythromycin extraction. © 2000 Society of Chemical Industry     

Prediction of the n‐hexane/water and 1‐octanol/water partition coefficients for environmentally relevant compounds using molecular simulation

In recent years molecular simulation has emerged as a useful tool to predict physical properties of complex chemical systems. A methodology to estimate the n‐hexane/water and 1‐octanol/water partition coefficients of environmentally relevant solutes, namely substituted alkyl‐aromatic molecules, chlorobenzenes, polychlorinated biphenyls (PCBs) and polychlorinated diphenyl ethers (PCDEs) using molecular simulation is elucidated here. The partition coefficients are calculated based on the absolute solvation Gibbs energies in each phase which are estimated from molecular dynamics simulations employing the thermodynamic integration approach. Very encouraging results, with average absolute deviations of 0.4 log P units are presented. Consequently, this molecular‐based approach with a strong physical background can provide reliable prediction of the partition coefficients in different solvent pairs without the a priori knowledge of experimental data. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1929–1938, 2012     

Solvent Effects on Fructose Dehydration to 5-Hydroxymethylfurfural in Biphasic Systems Saturated with Inorganic Salts

Furan derivatives, such as 5-hydroxymethylfurfural (HMF), obtained from acid-catalyzed dehydration of carbohydrates, can serve as renewable chemical platforms for the production of fuels and chemical intermediates. Addition of an inorganic salt to concentrated aqueous solutions of fructose (30 wt% fructose on salt free basis) in biphasic systems containing an organic extracting phase improves HMF yields by increasing the partitioning of HMF into the extracting phase, as measured by the partition coefficient, R, equal to the concentration of HMF in the organic phase normalized by the concentration in the aqueous phase. We have studied the impact of solvent choice on HMF yield using primary and secondary alcohols, ketones, and cyclic ethers in the C₃–C₆ range as extracting solvents in biphasic systems saturated with NaCl. Biphasic systems containing C₄ solvents generated the highest HMF yields within each solvent class. Tetrahydrofuran demonstrated the best combination of high HMF selectivity (83%) and high extracting power (R = 7.1) at 423 K. The presence of NaCl provided the additional benefit of creating biphasic systems using solvents that are completely miscible with water in the absence of salt. We have also studied the impact of different salts on HMF yield in systems using 1-butanol as the extracting solvent. Na⁺ and K⁺ showed the best combination of extracting power and HMF selectivity of the monovalent and divalent chloride salts tested. Changing the anion of the salt from Cl⁻ to Br⁻ resulted in R-values and HMF selectivity values resembling the non-salt system, while changing to the SO₄ ²⁻ divalent species generated a high R-value (8.1), but a low HMF selectivity value (71%).     

PARTITIONING BEHAVIOR OF PORPHYRIN DYES IN AQUEOUS BIPHASIC SYSTEMS

ABSTRACT

The partition of protoporphyrin IX and the phthallocyanine dye, propyl astra blue iodide, in aqueous biphasic systems (ABS) and onto aqueous biphasic extraction chromatographic (ABEC?) resins has been examined. Solubility of protoporphyrin IX was found to be too low for recovery by ABS other than by use of thermoseparating surfactants. Partitioning behavior of the phthallocyanine dye was found to depend on the salting-out strength of the salt. As a result of the partition of this dye to the interface of ABS, the adoption of ABEC for recovery of this dye is more favorable.     

Selective partition of caffeine from coffee bean and guaraná seed extracts using alcohol–salt aqueous two-phase systems

This work proposes the application of flexible alcoholic aqueous two-phase systems to manipulate the partition of caffeine. An optimization study was performed the caffeine partitioning towards top phase (60.0 wt% 2-propanol + 20.0 wt% K₃PO₄ at 303 K – K_caf = 3.4 and R_T = 89.1%) and bottom phase (60.0 wt% methanol + 17.5 wt% K₂HPO₄/KH₂PO₄ at 278 K – K_caf = 0.06 and R_B = 81.1%). These processes were evaluated by applying them to real biomass as guaraná seeds (purification factor (PF) = 6.59-fold) and coffee beans (PF = 3.24-fold) for the 2-propanol and K₂HPO₄/KH₂PO₄ system.     

SOLVENT EXTRACTION OF SOME TERVALENT LANTHAN01DS WITH 5-BR0M0-, 3,5-DIBROMO- AND 5-NITROSALICYLALDEHYDE ACETOHYDRAZONES

ABSTRACT

5-Bromo-, 3,5-dibromo- and 5-nitrosalicylaldehyde acetohydrazones (BSAH, DBSAH and NSAH, respectively, or H₂L) were synthesized. The extraction of lanthanoid ions (Ln3+) including praseodymium, europium and ytterbium ions into 1,2-dichloroethane with the synthesized hydrazones in the presence of both tri-n-butylphos-phate (TBP) and perchlorate has been investigated. The extracted species were (Ln³⁺)(HLP^?)₂(TBP)₃(CI₄ ^?) for all the hydrazones. The acid dissociation constants, Ka, and the partition coefficients, K_o, of the hydrazones and the extraction constants, K_ex, of the lanthanoid complexes were determined. The introduction of electron-withdrawing bromo or nitro groups to the 3- and/or 5-position of the benzene ring in salicylaldehyde acetohydrazone (SAH), the mother compound of the synthesized hydrazones, was very effective for increasing not only the K_ex value of SAH but also its K_D value and the K_ex values of its lanthanoid complexes. Taking into consideration the above-mentioned three constants, of the synthesized hydrazones DBSAH was the most balanced and recommend-able extractant for the lanthanoids.     

Synergistic Extraction of Th(IV) by Mixtures of HTTA and TBP in Benzene

Abstract

Extraction of Th(IV) from dilute perchloric acid medium by mixtures of HTTA and TBP in benzene medium was studied. The species Th(TTA)₄ TBP was found responsible for the observed synergism. Equilibrium constants for the extraction equilibria involved are log K_A = 2.25, log K_AB = 6.88, and log β_AB = 4.63.