Ana I. Alonso

Extraction of Cr(VI) with aliquat 336 in hollow fiber contactors: mass transfer analysis and modeling

In this work the mass transfer analysis and modeling of the hollow fiber non-dispersive liquid—liquid extraction of Cr(VI) with Aliquat 336 is reported. Experimental results corresponding to different values of the initial concentration of Cr(VI) in the aqueous phase in the range 50 g/m3 ⩽ C0 ⩽ 500 g/m3 showed three different diffusional regimes depending on both the initial concentration of Cr(VI) and the linear velocities of the aqueous phase: (i) kinetic control of the mass transport in the aqueous phase, (ii) kinetic control of the mass transport through the membrane fiber wall and (iii) an intermediate region where the control is shared between the aqueous and the membrane phases. The integration of the mass conservation equation with a nonlinear equilibrium condition at the fiber wall agrees satisfactorily with the results of experiments performed at different initial concentrations of Cr(VI) and different values of the linear velocity of the aqueous phase in the range C0 ⩾ 50 g/m3 and 2.95 × 10−3 m/s ⩽ v ⩽ 1.18 × 10−2 m/s. An optimization of the parameters D, solute diffusivity in the aqueous phase, and Keq, equilibrium constant of the extraction chemical reaction, with all the experimental results, using as criterion the minimum weighted standard deviation, gave as a result the value of the parameter D = 2.3 × 10−9 m2/s and values of Keq dependent upon the initial concentration of Cr(VI) in the feed solution. The mass transfer model and parameters reported in this work are useful for the design and optimization of the nondispersive extraction of Cr(VI) in a hollow fiber module.

Separation of Cr(VI) with aliquat 336: Chemical equilibrium modeling

Abstract The separation of chromium(VI) from industrial wastewaters is of great interest mostly due to the high toxicity of this metal. Although the extraction of Cr(VI) with anionic extractants (and among them, quaternary ammonium salts) has been widely studied using different technologies, a suitable equilibrium model it has not been reported due to the complex behavior of the organic phase. In this work a general methodology for modeling of the chemical equilibrium of Cr(VI) is presented. Discrimination between mathematical models that take account of the nonideal behavior of the organic phase led to the selection of a one-parameter empirical function of the total extractant concentration. K = K ccn o. The parameter values estimated for this model are the equilibrium constant (Kp = 0.197) and the fitting parameter (n = 0.661). and they are used in the expression for the description of the extraction equilibrium: This equation can satisfactorily describe the experimental behavior of chromi-um(VI) extrac...

Separation of L-Phenylalanine by Nondispersive Extraction and Backextraction. Equilibrium and Kinetic Parameters

ABSTRACT The objective of this work is the evaluation of the separation/concentration of L-phenylalanine by means of nondispersive extraction and backextraction in hollow fiber modules and the determination of the equilibrium and kinetic parameters, which will allow the description of the separation process. An organic solution based on Aliquat 336, 30% (v/v); isodecanol, 30% (v/v); and kerosene is used as a selective extraction medium. The extraction of L-phenylalanine takes place at pH 10·5, and the backextraction takes place at pH 0·5, with a sulfuric acid solution. The nondispersive extraction and backextraction process for the separation/con-centration of L-phenylalanine is described by means of a mathematical model based on seven differential equations. Its resolution is performed by the gPROMS simulation package after introduction of the chemical equilibrium extraction parameters KqE = 1·32 and K1 = 1·25 × 10−3 allowing calculation of the optimum value of the mass transfer coefficient, KM = 1·12 × ...

The GHEP–EMPOP collaboration on mtDNA population data—A new resource for forensic casework

Mitochondrial DNA (mtDNA) population data for forensic purposes are still scarce for some populations, which may limit the evaluation of forensic evidence especially when the rarity of a haplotype needs to be determined in a database search. In order to improve the collection of mtDNA lineages from the Iberian and South American subcontinents, we here report the results of a collaborative study involving nine laboratories from the Spanish and Portuguese Speaking Working Group of the International Society for Forensic Genetics (GHEP-ISFG) and EMPOP. The individual laboratories contributed population data that were generated throughout the past 10 years, but in the majority of cases have not been made available to the scientific community. A total of 1019 haplotypes from Iberia (Basque Country, 2 general Spanish populations, 2 North and 1 Central Portugal populations), and Latin America (3 populations from São Paulo) were collected, reviewed and harmonized according to defined EMPOP criteria. The majority of data ambiguities that were found during the reviewing process (41 in total) were transcription errors confirming that the documentation process is still the most error-prone stage in reporting mtDNA population data, especially when performed manually. This GHEP–EMPOP collaboration has significantly improved the quality of the individual mtDNA datasets and adds mtDNA population data as valuable resource to the EMPOP database (www.empop.org).

Nondispersive Extraction of Cr(VI) with Aliquat 336: Influence of Carrier Concentration

Abstract Kinetic experiments on the extraction of Cr(VI) with Aliquat 336 performed in hollow fiber modules and in the 1% (v) ≤ Aliquat 336 ≤ 10% (v) and 10 g/m3 ≤ Cr(VI) ≤ 500 g/m3 range of concentrations have been successfully modeled by means of the integration of the mass conservation equation and associated boundary conditions. Different values of the mass transport coefficient through the organic membrane have been obtained depending on the total carrier concentration.

Study of six X-linked tetranucleotide microsatellites: population data from five Spanish regions

We studied six X-linked microsatellites in a large group of Spanish individuals (n=614) from five different regions located in northern, central and southern Spain. All the markers had tetranucleotide repeat units (DXS9895, DXS9898, DXS7130, DXS7132, GATA172D05 and DXS6789). They were amplified in two triplex PCR reactions. There were no significant sex- or region-related differences in allelic frequencies, suggesting that general national databases can be adequate as a reference for X-linked markers. The analysis of those six short tandem repeats combined in 316 males revealed 300 different “temporary haplotypes”, 283 of which were found only once. There was no evidence for statistically significant linkage disequilibrium among the loci studied. Therefore these markers are quite polymorphic and useful for forensic purposes.

Optimal operation of selective membrane separation processes for wastewater treatment

Abstract The objective of this work is to identify and select optimally the main operating conditions of selective membrane separation processes for wastewater treatment. The advantage of this technology is that it reduces the amount of metals disposed into the environment, by removing them from wastewater and concentrating them simultaneously in the stripping stream for re-use in the plant that generates the effluent. The operating conditions are evaluated solving an optimisation problem, where the set of algebraic and differential equations that represent the component mass balances are formulated as equality constraints, together with the separation objectives that are posed as inequality end point constraints. The optimisation leads to significant improvements in terms of the flow rate of the effluent treated, showing the potential of the methodology presented. Insight on the dynamic behaviour of the selective membrane separation processes is gained through the sensitivity analysis.

PHENOL RECOVERY WITH SLM USING “CYANEX 923”

Abstract The study of the phenol separation-concentration process with the hollow fiber supported liquid membrane technology has been performed. Mixtures of kerosene and CYANEX 923 were used as liquid membrane. The extractant CYANEX 923 is characterized by a high phenol selectivity and an extremely low solubility in the aqueous phase. The introduction of CYANEX 923 in the membrane composition decreases the extractant losses from the pores of the support. The phenol separation and simultaneous concentration process has been checked. The influences of the initial concentration of phenol in the feed solution and sodium hydroxide in the stripping phase and the membrane composition on the separation rate have been investigated in a single-pass mode. The analysis of the membrane composition influence has been performed according to the steady-state mass transfer conservation equation and the associated boundary conditions, leading to the mass transfer parameters of the process

Optimal design of non-dispersive solvent extraction processes

Abstract The purpose of this paper is to carry out the optimal design of a non-dispersive solvent extraction (NDSX) process for the removal and recovery of chromium from waste waters of surface treatment industries. The objective is to design a process that can separate the waste stream into an environmentally acceptable stream with a low chromium concentration and a stream in which chromium is concentrated for further processing. A superstructure of the problem which is rich enough to account for all potential configurations and connectivity of the system is proposed. The problem is formulated as a MINLP optimisation problem to minimise the total cost of the process subject to design specifications and is solved using an Outer Approximation algorithm. The nonconvexivity of the problem due to bilinear terms in the model equations makes necessary the reformulation of the nonconvex equations into linear inequalities. Three different approaches are tried for this reformulation. A bound tightening strategy based on the application of branch and bound methods to the Outer Approximation algorithm is shown to be the most effective approach.

Cuidados paliativos en la enfermedad pulmonar intersticial difusa: resultados de una encuesta de ámbito nacional

INTRODUCTION Interstitial lung diseases (ILD) and, in particular, idiopathic pulmonary fibrosis, may have a significant impact on patient survival. Recent studies highlight the need for palliative care (PC) in the management of ILD patients. The aim of this study was to determine the current situation of PC in patients in Spain. METHODS A 36-question survey addressing the main aspects of PC in ILD patients was designed. The survey was sent via email to all members of the Spanish Society of Pulmonology and Thoracic Surgery. Participation was voluntary. RESULTS One hundred and sixty-four participants responded to the survey. Ninety-eight percent said they were interested in PC, 46% had received specific training, and 44% reported being responsible for PC in their ILD patients. Symptom control and end-of-life stage were the most frequent reasons for referral to PC teams. Regarding end-of-life, 78% reported consensual agreement with patients on the limitation of therapeutic efforts, 35% helped prepare an end-of-life advance directive, and 22% agreed on the place of death. CONCLUSION Despite the well-known need for PC in patients with ILD and the notable interest of the survey participants in this subject, there are clear formative and organizational gaps that should be addressed to improve care in this area in ILD patients in Spain.