Eugenio Bringas

Arsenic and fluoride contaminated groundwaters: A review of current technologies for contaminants removal.

Chronic contamination of groundwaters by both arsenic (As) and fluoride (F) is frequently observed around the world, which has severely affected millions of people. Fluoride and As are introduced into groundwaters by several sources such as water-rock interactions, anthropogenic activities, and groundwater recharge. Coexistence of these pollutants can have adverse effects due to synergistic and/or antagonistic mechanisms leading to uncertain and complicated health effects, including cancer. Many developing countries are beset with the problem of F and As laden waters, with no affordable technologies to provide clean water supply. The technologies available for the simultaneous removal are akin to chemical treatment, adsorption and membrane processes. However, the presence of competing ions such as phosphate, silicate, nitrate, chloride, carbonate, and sulfate affect the removal efficiency. Highly efficient, low-cost and sustainable technology which could be used by rural populations is of utmost importance for simultaneous removal of both pollutants. This can be realized by using readily available low cost materials coupled with proper disposal units. Synthesis of inexpensive and highly selective nanoadsorbents or nanofunctionalized membranes is required along with encapsulation units to isolate the toxicant loaded materials to avoid their re-entry in aquifers. A vast number of reviews have been published periodically on removal of As or F alone. However, there is a dearth of literature on the simultaneous removal of both. This review critically analyzes this important issue and considers strategies for their removal and safe disposal.

Selective Separation of Zinc and Iron from Spent Pickling Solutions by Membrane-Based Solvent Extraction: Process Viability

Abstract This work reports the viability of the selective separation of zinc from spent pickling solutions by means of membrane‐based solvent extraction to get a high concentrated zinc solution with a negligible content of iron and other metals that could be used in a electrolytic process to recover zinc in a metallic form. By working with waste effluents as feed solutions that contained these main components, Zn 78 g/L av., Fe 90 g/L av., and HCl 237 g/L av., Tributyl phosphate (TBP) and water were selected as the extractant and back‐extraction agent that allowed maximum zinc separation and recovery. With the kinetic results obtained in a bench‐scale set‐up containing two hollow fiber (HF) modules the selectivity of zinc over iron recovery, αZn/Fe, was calculated. The parameter αZn/Fe depended on the initial metallic concentration in the feed solutions and reached a maximum value of αZn/Fe = 146 (g Zn/g Fe).

Optimal synthesis of an emulsion pertraction process for the removal of pollutant anions in industrial wastewater systems

Abstract This work reports a synthesis model for the optimal design of an emulsion pertraction process for the removal and recovery of pollutant anions from industrial wastewaters. The goal is to define the minimum membrane area needed in order to obtain an environmentally acceptable stream with minimum concentration of the pollutant and at the same time a concentrated solution for further processing. A superstructure is proposed which consists of a prespecified number of modules that are interconnected in all possible ways in order to account for all potential configurations. The selection of the optimal design from this superstructure is formulated as a non-linear programming (NLP) problem that is solved with CONOPT2 from GAMS. In order to reduce the membrane area, alternative configurations that provide flexibility to the emulsion phase inlet and higher residence time values were analyzed obtaining 56% reduction of the membrane area.

Development and validation of a dynamic model for regeneration of passivating baths using membrane contactors

This work aims at the development of a dynamic model for the mathematical description of facilitated transport separation processes carried out in membrane contactors where mass transport phenomena are coupled with chemical reactions. A general model that takes into account the description of all possible mass transport steps and interfacial chemical reactions is initially presented, allowing its application to a wide range of separation processes and operation conditions. The analysis of the specific system under study, regeneration of trivalent chromium spent passivating baths by removal of zinc using the emulsion pertraction technology, allowed to define several assumptions obtaining simplified models with minimum number of uncertain parameters and mathematical complexity. The final equations and parameters were validated with experimental data reported in a previous work (Urtiaga, Bringas, Mediavilla, & Ortiz, 2010).

Membrane contactors (NDSX and EPT): an innovative alternative for the treatment of effluents containing metallic pollutants

This work presents an overview of membrane-based solvent extraction technologies using membrane contactors as an innovative alternative for the remediation of effluents containing metallic pollutants. The discussion is focused on the description of Non-Dispersive Solvent Extraction (NDSX) and Emulsion Pertraction Technologies (EPTs). Three case studies are reported to demonstrate the viability of NDSX and EPT for the removal and recovery of metallic pollutants present in aqueous streams:

Development and Validation of a Dynamic Model for Regeneration of Passivating Baths using Membrane Contactors

Abstract Selective liquid membranes have been traditionally employed for liquid/liquid and gas/liquid mass transfer in a wide range of applications. In particular, the Emulsion Pertraction Technology (EPT) using hollow fiber membrane contactors is a promising alternative to carry out the selective separation of metals from complex mixtures. However, the application of a new technology requires of reliable mathematical models and parameters that serve for design and optimization purposes allowing to accurate scale-up processes. This work reports the methodology for the development of a dynamic model to describe the kinetics of the EPT separation-concentration process applied to the regeneration of spent trivalent chromium-based passivating baths. The regeneration stage aims at the selective removal of Zn2+ dragged from previous steps in the plating line, not affecting the level of Cr3+ concentration in the passivating bath. In the case study the mathematical model was initially developed in a rigorous way and in a further analysis, a systematic method for its simplification was established. Then, the system of partial differential and algebraic equations obtained was integrated using the commercial software package ASPEN CUSTOM MODELER (from ASPENTECH) making possible the analysis of the model sensibility under different values of the operation variables. Finally, the model was validated with kinetic data obtained at laboratory scale.

Membrane Operations for the Recovery of Valuable Metals from Industrial Wastewater

The development of separation technologies, which also permit the recovery of valuable compounds from industrial wastewaters, reports economic and environmental benefits. In particular, the selective recovery of metals from end-of-life products is an essential strategy to avoid the depletion of natural sources, especially for less abundant metals such as rare earths (REs) and platinum-group metals (PGMs). Although several technologies have been applied in the recovery of metals from wastes, solvent extraction reported the best performance in terms of selectivity when complex matrixes are treated. Regarding solvent extraction, the use of membrane contactors raises against the conventional contactors due to their diverse advantages such as the high interfacial area/volume ratio, the prevention of emulsion formation, the modular design that simplifies the process scale-up and the lower operation cost. This work evaluates the benefits of membrane-based solvent extraction technologies to recover metallic compounds from waste materials through three different cases of study: (i) zinc recovery from spent pickling solutions, (ii) PGMs recovery from depleted car catalytic converters and (iii) rare earths recovery from waste electrical and electronic devices.

Computational analysis of facilitated transport in a microfluidic device

Abstract Microfluidic technology reports many advantages to be used in solvent extraction, namely reduced volume of the receptor phase, ease control of the fluidynamics of both liquid phases and thus, improved process performance. This work reports the theoretical, through CFD computational simulation, and experimental analysis of a microfluidic extraction process. For this purpose, the extraction of hexavalent chromium from aqueous phases has been selected as a motivating example. First, the diffusive separation in a system with two homogeneous phases, and then its carrier-mediated facilitated transport through a water-organic interface are analysed. Experimental results fit satisfactory well to model simulations with an error less than 10% demonstrating the reliability of the developed model for both scenarios.

Computational Analysis of a Two-Phase Continuous-Flow Magnetophoretic Microsystem for Particle Separation from Biological Fluids

Abstract In recent years, there has been growing interest in the use of functionalized magnetic beads for biomedical applications due to the outstanding characteristics of these materials. Furthermore, the recent development of microfluidics has enabled the continuous capture of malignant cells or toxins from biofluids for either analysis or treatment. However, the optimization of these processes has been relatively less studied and rational design is often lacking because of the complexity associated to their mathematical description. In this work, the separation of magnetic beads from flowing blood streams inside a multiphase system is analyzed through CFD techniques. The numerical model introduces a coupled magnetic and fluidic analysis that describes the bead trajectories under magnetic gradients generated by permanent magnets. A key feature of this work is that we studied for the first time the interaction between two fluids flowing simultaneously in the device while taking into account the effects of particle-fluid interactions in the flow field. Magnetic and fluidic forces on the particles are studied and optimized through a dimensionless number J. The results show that complete particle separation avoiding any mixing or perturbation of the fluids can be achieved for a certain range of the J number.