M. Rosinda C. Ismael

Studies on the Use of Ionic Liquids as Potential Extractants of Phenolic Compounds and Metal Ions

Abstract The present work was aimed at investigating the usefulness of 1‐(n‐alkyl)‐3‐methylimidazolium‐derived ionic liquids (ILs) in liquid–liquid separation processes. For this purpose, a series of 1‐(n‐alkyl)‐3‐methylimidazolium tetrafluoroborates and hexafluorophosphates were prepared by standard synthetic methods and characterized by 1H NMR. Experiments were performed to assess the influence of the alkyl group and the anion on the physical properties of the IL. Equilibrium studies on the extraction of heavy metal ions (copper, zinc, and chromium) and some common pollutant aromatic compounds (phenol, tyrosol, and p‐hydroxybenzoic acid) from aqueous media then were performed with some selected ILs. The effects of temperature and the pH on the distribution ratio of solutes between the IL/aqueous phases also were analyzed. The results suggest that some of the ionic liquids tested are adequate to extract metal ions and organic compounds from aqueous solutions, with a high efficiency in some instances.

Removal of phenols from aqueous solutions by emulsion liquid membranes

The present study deals with the extraction of phenols from aqueous solutions by using the emulsion liquid membranes technique. Besides phenol, two derivatives of phenol, i.e., tyrosol (2-(4-hydroxyphenyl)ethanol) and p-coumaric acid (4-hydroxycinnamic acid), which are typical components of the effluents produced in olive oil plants, were selected as the target solutes. The effect of the composition of the organic phase on the removal of solutes was examined. The influence of pH of feed phase on the extraction of tyrosol and p-coumaric was tested for the membrane with Cyanex 923 as an extractant. The use of 2% Cyanex 923 allowed obtaining a very high extraction of phenols (97-99%) in 5-6 min of contact time for either single solute solutions or for their mixtures. The removal efficiency of phenol and p-coumaric acid attained equivalent values by using the system with 2% isodecanol, but the removal rate of tyrosol was found greatly reduced. The extraction of tyrosol and p-coumaric acid from their binary mixture was also analysed for different operating conditions like the volume ratio of feed phase to stripping phase (sodium hydroxide), the temperature and the initial concentration of solute in the feed phase.

Copper extraction from ammoniacal medium in a pulsed sieve-plate column with LIX 84-I

This article reports on a study of copper removal from ammoniacal aqueous solution (1.0 kg m(-3) Cu, pH 9.5) by liquid-liquid extraction using a pulsed sieve-plate column. The extractant tested was the hydroxyoxime LIX 84-I (2-hydroxy-5-nonylacetophenone oxime) in the aliphatic diluent Shellsol D-70. The results of the pilot plant experiments demonstrated the feasibility of operating the extraction process in this type of column, with efficiencies of copper removal in the range of 90.5-99.5%. Several effects on the column performance were examined, namely the aqueous and organic flow rates and the pulse velocity. The axial dispersion model was applied to simulate the concentration profiles, which reasonably predicted the experimental data. The overall mass transfer coefficient was evaluated from the experimental data and was found to be between 9×10(-6) and 1.2×10(-5) m s(-1). These data were compared with the ones obtained from the resistances in series model, which indicated that the resistance due to chemical reaction was 84-91% of the overall resistance to mass transfer. The extraction using a hollow fiber contactor was also carried out to compare the membrane process performance with the one of conventional process.

Modeling of the Extraction Equilibrium of Copper from Sulfate Solutions with Acorga M5640

The extraction equilibrium of copper from sulfate media with the aldoxime Acorga M5640 in ShellSol D70 has been investigated. The distribution results were interpreted by taking into account the nonideality of the aqueous phase. The activity of copper and hydrogen ions in the target systems CuSO4/H2SO4/Na2SO4 and CuSO4/H2SO4/Fe2(SO4)3/ZnSO4 were calculated through the speciation of the aqueous solutions and by applying the Pitzer model. The experimental pH values were found in good agreement with the predicted pH values. A model considering the dimerization of the aldoxime extractant was proposed to predict the distribution ratio and the copper loading isotherms. The extraction constant at infinite dilution and the apparent dimerization constant were evaluated from the experimental data and were found to be 103.06 ± 0.07 and 51 ± 9 M−1, respectively, at 25°C.

Extraction of Copper from Aqueous Solutions by Liquid Membrane Processes

The removal and recovery of copper from aqueous solutions using hollow‐fiber membrane contactors were studied. Single extraction was performed at different flow rates of phases, the concentrations of LIX 84‐I in the membrane, the contents of copper in the feed phase, and the aqueous media. The overall mass transfer coefficient for copper extraction was calculated from the experimental data and was also evaluated by the conventional resistance in series model. The relative contribution of the resistance due to the chemical reaction to the overall resistance to mass transfer was found significant. The integration of the extraction and stripping stages was carried out in two hollow‐fiber modules. A few tests were also carried out with LIX 54 as a carrier for comparison. The results obtained showed that practically all the copper content was removed and recovered from the ammoniacal and sulfuric feed solutions. The results were then compared with the ones obtained by applying the emulsion liquid membranes technique. Finally, the emulsion phase with LIX 84‐I was used in a single hollow‐fiber module to perform an extraction‐stripping experiment.

Extraction of Cu(II) with Acorga M5640 using hollow fibre liquid membrane

The extraction of copper from sulphuric/sulphate solutions using a hollow fibre module as contactor was studied. The aldoxime Acorga M5640 was used as an extractant. The effects on the extraction rate of the flow-rates, the concentrations of copper and extractant, pH, and the presence of Na2SO4 in the feed phase were investigated. The overall mass transfer coefficient for copper extraction was calculated from the experimental data and was compared with the value evaluated by the resistance in the series model. The extraction process was found to be governed by the diffusion in the boundary aqueous layer and also by the chemical reaction. The kinetic data obtained were used to simulate the extraction of copper with the pseudo-emulsion-based hollow fibre with strip dispersion technique. The accordance between the results thus calculated and the experimental data was found to be satisfactory, particularly for dilute feed solutions.

A study on a combined process for the treatment of phenolic resin plant effluents

The removal of phenol and formaldehyde from phenolic resin plant effluents has been studied by using a combined process. In the first step, phenol was removed from effluent by solvent extraction. Special attention was paid to the effluent with a low content of phenol, which was treated by non-dispersive solvent extraction in hollow fibres. It was found that a single module of Liqui-Cel 2.5in. x 8in. membrane contactor allowed processing approximately 24 L/h of effluent with 0.4-0.7 g/L phenol and attaining values as low as 0.5 mg/L in the raffinate. Formaldehyde, which was left in phenolic resin plant effluent after the removal of phenol, has been treated with hydrogen peroxide in alkaline medium and also in acidic medium (Fenton process). In alkaline medium, formaldehyde was oxidized with hydrogen peroxide to formate ion, which was recovered by solvent extraction. The oxidation of formaldehyde with Fenton process was also studied under several operating conditions. It was found that a large amount of hydrogen peroxide (i.e. mole ratio H(2)O(2):HCHO>6) was necessary to mineralize more than 90% HCHO in 1-2h, at atmospheric pressure and 25 degrees C. The combination of pressure and high temperature strongly increased the kinetics of the process and allowed achieving a very high overall efficiency of the treatment under moderate H(2)O(2) dosage.

Extraction of 4‐Hydroxybenzoic Acid with Aliquat 336: Equilibrium Studies

Abstract This paper reports a study of the extraction of 4‐hydroxybenzoic acid with a mixture of trialkylmethylammonium chlorides (Aliquat 336) dissolved in a mixture of ShellSol T and ShellSol A. The experimental results revealed that the extraction of undissociated 4‐hydroxybenzoic acid (HA) with Aliquat 336 (QCl) can be described by the following equation: while the extraction of anionic 4‐hydroxybenzoic acid (A−) with Aliquat 336 is described by the following equation: The thermodynamic equilibrium constants in terms of the aqueous phase for the reactions above were evaluated to be, respectively, K 1,ext 0=10(2.18±0.15) and K 2,ext 0=10(0.81±0.11) at 298 K. The non‐ideality of the aqueous phase was taken into account by applying a Setchenov equation for non‐dissociated 4‐hydroxybenzoic acid, the extended Debye–Hückel equation for dissociated 4‐hydroxybenzoic acid, and the Pitzer model for other species in the aqueous solution. The use of K 1,ext 0 and K 2,ext 0 equilibrium constants allowed simulating the dependence of the distribution coefficient (D) on pH in the range 1.5–8.5. The equilibrium results showed that the presence of 1‐decanol (ROH) in the organic phase complicates the extraction process. This can be explained by an interaction between QCl and ROH, which reduces the concentration of free QCl. The formation of QCl:ROH species in the organic phase was postulated and the correspondent equilibrium constant was found to be (3.3±0.3)/M.

Recovery of hydrochloric acid from galvanizing industrial effluents

ABSTRACT The recovery of hydrochloric acid and its separation from iron, zinc and minor elements, in the galvanizing pickling baths, were studied by solvent extraction (SX) and distillation and by distillation and crystallization. Several extractants were tested, the tri-isooctyl amine, Alamine 308, the primary aliphatic amine Primene JM-T and the mixture of four trialkylphosphine oxides, Cyanex 923. Only Cyanex 923 enabled distillation. The results indicated the feasibility of the processes to treat a real effluent using Cyanex 923 and to obtain high HCl concentrations in the distillate (256–330 g/L).

Selective Separation and Recovery of Zinc and Lead from Galvanizing Industrial Effluents by Anion Exchange

The recovery of zinc and its separation from iron, hydrochloric acid, and minor elements in the galvanizing pickling baths were studied by anion exchange. The breakthrough curves demonstrated that the resins, Lewatit MonoPlus MP 500 and AMBERLYST A21, exhibit a greater capacity for zinc than for cadmium, copper, and lead. The results indicated the feasibility of operating the ion exchange process to treat a real effluent. During the loading, lead started eluting until its complete removal from the resin. Like this, a two-step removal solution is proposed, using two columns with Lewatit MonoPlus MP 500, for separating zinc and lead.