M. Lurdes F. Gameiro

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.

Bipolar Electrochemistry, a Focal Point of Future Research

Bipolar electrochemistry is a conventional method based on the polarization of an isolated substrate under an applied electric field. This technique has been applied to electrolysis, corrosion, and other areas of chemical engineering since the twentieth century. However, it has been recognized as a powerful tool in many modern domains after water splitting has been demonstrated to be possible using micrometer-sized bipolar electrodes. Modifying inorganic objects in novel ways, such as creating electrical contacts between metal particles using directed electrochemical growth or shaping and exploring the micro- and nanoworld are some of the new applications in this field. Fabrication of electronic devices, electroanalytical purposes, generation of molecular and material gradients, functionalization of single micro- and nanopores, synthesis of Janus particles, design of swimmers, and asymmetric modification of nanoparticles will be discussed in this article as a focal point of future research in bipolar electrochemistry.

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 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.

Dewatering of brewer’s spent grain using an integrated membrane filter press with vacuum drying capabilities

ABSTRACT Brewer’s spent grain (BSG) is a by-product of the brewing process, rich in fiber, protein and carbohydrates. Its potential application is limited because of high moisture content (80%). This work presents a process for dewatering BSG using two different sets of membrane filter plates in a filter press with vacuum drying: recessive plates with polypropylene membranes and the innovative Rollfit® plates. A final moisture content of 12-15% was obtained in 15 mm-thick filter cakes, using both types of plates. The dewatering cycle included filtration, membrane-squeezing, and vacuum thermal drying using hot water (~90ºC) as heat source.