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Within the current climate emergency framework and in order to avoid the most severe consequences of global warming, membrane separation processes have become critical for the implementation of carbon capture, storage, and utilization technologies. Mixtures of CO2 and CH4 are relevant energy resources, and the design of innovative membranes specifically designed to improve their separation is a hot topic. This work investigated the potential of modified polydimethylsiloxane and ionic liquid-chitosan composite membranes for separation of CO2 and CH4 mixtures from different sources, such as biogas upgrading, natural gas sweetening, or CO2 enhanced oil recovery. The techno-economic optimization of multistage processes at a real industrial scale was carried out, paying special attention to the identification of the optimal configuration of the hollow fiber modules and the selection of the best membrane scheme. The results demonstrated that a high initial content of CH4 in the feed stream (like in the case of natural gas sweetening) might imply a great challenge for the separation performance, where only membranes with exceptional selectivity might achieve the requirements in a two-stage process. The effective lifetime of the membranes is a key parameter for the successful implementation of innovative membranes in order to avoid severe economic penalties due to excessively frequent membrane replacement. The scale of the process had a great influence on the economic competitiveness of the process, but large-scale installations can operate under competitive conditions with total costs below 0.050 US$ per m3 STP of treated feed gas. This work was funded by the Spanish Ministry of Science and Innovation Project PID2019-108136RB-C31/AEI/10.13039/501100011033. MCIN/AEI/10.13039/501100011033 and the “European Union NextGeneration EU/PRTR” are also thanked for the grant EIN2020-112319/AEI/10.13039/501100011033.

Slowing down climate change requires urgent measures, and consequently, one of the main challenges of the scientific community is to develop innovative technologies to reduce carbon dioxide emissions to the atmosphere. Non-dispersive CO2 absorption using ionic liquids (ILs) as solvent and membrane vacuum regeneration (MVR) as desorption step are considered as a one of the most promising technologies for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity carbon dioxide streams are needed for technical valorization approach. In this work, the chemical binding 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) and the physical solvent 1-ethyl-3-methylimidazolium methyl sulfate ([emim][MS]) have been selected. COSMO based/Aspen Plus methodology has been successfully executed to specify the COSMOSAC property method used in the commercial process simulator (Aspen Plus). Besides, a detailed two-dimensional mathematical model of MVR technology has been validated for the first time with [emim][MS] as a representative of physical ionic liquid solvent. The effect on CO2 desorbed flux and process efficiency have been tested at different operation conditions in order to compare the behavior of chemical and physical absorption based on ionic liquids. Low vacuum pressure and high temperature show a positive influence in the solvent regeneration process, while high liquid flow-rate increases the process performance but also decrease the CO2 desorption. The IL ([emim][Ac]) presented higher MVR performance (92 %) than the IL [emim][MS] (83 %) at the best operational conditions (313 K and 0.04 bar), in which the total energy consumption has been estimated on 0.62 and 0.34 MJe·kgCO2−1, respectively. These results noted the benefit of the MVR technology based on ILs compared to the conventional amino-based high -temperature regeneration process (1.55 MJe·kgCO2−1), presenting a step forward in the substitution of amines. This work provides a valuable tool to help in the decision-making to select the most promising ionic liquids, reducing laboratory efforts and, consequently, experimental costs. This work has been funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), project CTQ2016-76231-C2-(AEI/FEDER, UE), project PID2019-108136RB-C31-(MCIN/AEI) and project PID2020-112845RB-I00-(MCIN/AEI). J.M.V. thanks the Concepción Arenal postgraduate research grant from the University of Cantabria.

Postcombustion carbon capture (PCC) using membrane technology is a rising alternative to PCC processes that are based on conventional equipment, such as CO2 absorption-desorption in packed columns, to mitigate human-associated climate change. Research on CO2 capture systems has centered on improving the CO2 absorption process efficiency, while little attention has been devoted to the performance of the solvent regeneration technology. In this review, research development is focused on the performance of the CO2 desorption process using hollow fiber membrane contactors. The main impact factors in membrane contactor technology are presented, including solvent and membrane material selection, membrane module design, mass transfer correlations, operational issues, modeling, and simulations. Each section is discussed in terms of its current status future challenges to improve the technology for its industrial implementation are described. This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), Project CTQ2016-76231-C2-(AEI/FEDER, UE) and Project PID2019-108136RB-C31). J.M.V. thanks the Concepción Arenal postgraduate research grant from the University of Cantabria.

A novel modelling and simulation framework on CO2 desorption process from post-combustion CO2 capture was developed by a coupled membrane vacuum regeneration technology (MVR) and four imidazolium ionic liquids (ILs) with remarkably different viscosity values. The ILs 1-ethyl-3-methylimidazolium acetate ([emim][Ac]), 1-butyl-3-methylimidazolium acetate ([bmim][Ac]), 1-butyl-3- methylimidazolium isobutyrate ([bmim][i-but]), 1-butyl-3-methylimidazolium glycinate ([bmim][GLY]) were selected. COSMO based/Aspen Plus methodology was effectively implemented to estimate the physical and chemical CO2 absorption parameters by kinetic and thermodynamic models fitted to experimental data to design the regeneration process in Aspen Plus software. The membrane contactor unit for solvent regeneration was custom-built and successfully imported into the simulation tool, as no model library for the MVR existed yet in the commercial package for the steady state process flowsheet simulation. The effect on CO2 desorbed flux and process performance was evaluated for the comparison purpose between ILs at different operational conditions. High temperature, vacuum level and module length are beneficial to the solvent regeneration process, while low liquid flow-rate increases the CO2 desorption flux but also decrease the process performance. The viscosity, CO2 solubility and reaction enthalpy were identified as key thermodynamic properties of IL selection. The IL ([emim][Ac]) presented the highest regeneration performance (around 92% at 313 K and vacuum pressure of 0.04 bar) with a total energy consumption of 0.62 MJ·kgCO2-1, which is lower than conventional amino-based high temperature regeneration process (1.55 MJ·kgCO2-1). These results pointed out the interest of the membrane vacuum regeneration technology based on ILs compared to the conventional solvent-based thermal regeneration, but further techno-economic evaluation is further needed to ensure the competitiveness of this novel CO2 desorption approach to the large-scale application. This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), project CTQ2016-76231-C2-(AEI/FEDER, UE) and project PID2019-108136RB-C31/ AEI / 10.13039/501100011033). J.M.V. thanks the Concepción Arenal postgraduate research grant from the University of Cantabria.

Membrane technology is a simple and energy-conservative separation option that is considered to be a green alternative for CO2 capture processes. However, commercially available membranes still face challenges regarding water and chemical resistance. In this study, the effect of water and organic contaminants in the feed stream on the CO2/CH4 separation performance is evaluated as a function of the hydrophilic and permselective features of the top layer of the membrane. The membranes were a commercial hydrophobic membrane with a polydimethylsiloxane (PDMS) top layer (Sulzer Chemtech) and a hydrophilic flat composite membrane with a hydrophilic [emim][ac] ionic liquid&ndash, chitosan (IL&ndash, CS) thin layer on a commercial polyethersulfone (PES) support developed in our laboratory. Both membranes were immersed in NaOH 1M solutions and washed thoroughly before characterization. The CO2 permeance was similar for both NaOH-treated membranes in the whole range of feed concentration (up to 250 GPU). The presence of water vapor and organic impurities of the feed gas largely affects the gas permeance through the hydrophobic PDMS membrane, while the behavior of the hydrophilic IL&ndash, CS/PES membranes is scarcely affected. The effects of the interaction of the contaminants in the membrane selective layer are being further evaluated.

The chemistry and electrochemistry basic fields have been active for the last two decades of the past century studying how the modification of the electrodes&rsquo, surface by coating with conductive thin films enhances their electrocatalytic activity and sensitivity. In light of the development of alternative sustainable ways of energy storage and carbon dioxide conversion by electrochemical reduction, these research studies are starting to jump into the 21st century to more applied fields such as chemical engineering, energy and environmental science, and engineering. The huge amount of literature on experimental works dealing with the development of CO2 electroreduction processes addresses electrocatalyst development and reactor configurations. Membranes can help with understanding and controlling the mass transport limitations of current electrodes as well as leading to novel reactor designs. The present work makes use of a bibliometric analysis directed to the papers published in the 21st century on membrane-coated electrodes and electrocatalysts to enhance the electrochemical reactor performance and their potential in the urgent issue of carbon dioxide capture and utilization.

The chemistry and electrochemistry basic fields have been active since the last two decades of the past century studying how surface modification of electrodes by coating with conductive films enhances their activity and performance. In the light of the development of alternative sustainable ways of energy storage and carbon dioxide conversion by electrochemical processes, these research studies have jumped in the 21st century to more applied fields such as chemical engineering, energy and environmental science and engineering. The huge amount of literature on experimental works dealing with the development of CO2 electroreduction processes addresses electrocatalyst development. Membranes can help understanding and controlling the mass transport limitations of current electrodes and reactors designs. The present bibliometric review addresses the papers published in the 21st century regarding membrane coated electrodes and electrocatalysts to enhance electrochemical reactor performance and viability with a special focus on the urgent issue of carbon dioxide capture and utilization.

In this work, the membrane vacuum regeneration (MVR) process was considered as a promising technology for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity CO2 is needed for a technical valorization approach. First, a desorption test by MVR using polypropylene hollow fiber membrane contactor (PP-HFMC) was carried out in order to evaluate the behavior of physical and physico-chemical absorbents in terms of CO2 solubility and regeneration efficiency. The ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was presented as a suitable alternative to conventional amine-based absorbents. Then, a rigorous two-dimensional mathematical model of the MVR process in a HFMC was developed based on a pseudo-steady-state to understand the influence of the solvent regeneration process in the absorption–desorption process. CO2 absorption–desorption experiments in PP-HFMC at different operating conditions for desorption, varying vacuum pressure and temperature, were used for model validation. Results showed that MVR efficiency increased from 3% at room temperature and 500 mbar to 95% at 310 K and 40 mbar vacuum. Moreover, model deviation studies were carried out using sensitivity analysis of Henry’s constant and pre-exponential factor of chemical interaction, thus as to contribute to the knowledge in further works.

Lignin is one of the three main components of lignocellulosic biomass and must be considered a raw material with attractive applications from an economic and ecological point of view. Therefore, biorefineries must have in mind the most adequate processing to obtain high-quality lignin and the separation tasks that play a key role to improve the purity of the lignin. Separation techniques based on membranes are a promising way to achieve these requirements. In this work, the separation performance of the SILM (Supported Ionic Liquid Membrane) formed with [BMIM][DBP] as IL (Ionic Liquid) and PTFE as membrane support was compared to a nanofiltration (NF) membrane (NP010 by Microdyn-Nadir) and two ultrafiltration (UF) membranes (UF5 and UF10 by Trisep). The SILM showed selective transport of Kraft lignin, lignosulphonate, xylose, and glucose in aqueous solutions. Although it was stable under different conditions and its performance was improved by the integration of agitation, it was not competitive when compared to NF and UF membranes, although the latter ones suffered fouling. The NF membrane was the best alternative for the separation of lignosulphonates from monosaccharides (separation factors around 75 while SILM attained only values lower than 3), while the UF5 membrane should be selected to separate Kraft lignin and monosaccharides (separation factors around 100 while SILM attained only values below 3). This research was funded by the Spanish Ministry of Economy and Competitiveness (MINECO), Project number CTQ2014‐56820‐JIN and co‐funded by FEDER.

The fractionation in an industrial-scale continuous process of a protein hydrolysate obtained from tuna wastes has been proposed. A model based on membrane transport equations, mass balances and economic equations to calculate the main costs of the process was developed. This model was applied to the evaluation of the main technical, environmental and economic aspects of the process and their optimization. The basic cascade configuration resulted better than alternative options like the linear or dual cascades. The freshwater consumption was minimized to improve the environmental and economic performance of the process. Indeed, the implementation of a water recovery and reuse system was the most effective solution. This system was based on the installation of an additional tight nanofiltration stage that reduced the environmental impact of the process (avoiding the need of auxiliary freshwater streams) and increased its economic competitiveness. This project has received financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through CTQ2014-56820-JIN Project, co-financed by FEDER funds.

The effective separation of CO2 and CH4 mixtures is essential for many applications, such as biogas upgrading, natural gas sweetening or enhanced oil recovery. Membrane separations can contribute greatly in these tasks, and innovative membrane materials are being developed for this gas separation. The aim of this work is the evaluation of the potential of two types of highly CO2-permeable membranes (modified commercial polydimethylsiloxane and non-commercial ionic liquid–chitosan composite membranes) whose selective layers possess different hydrophobic and hydrophilic characteristics for the separation of CO2/CH4 mixtures. The study of the technical performance of the selected membranes can provide a better understanding of their potentiality. The optimization of the performance of hollow fiber modules for both types of membranes was carried out by a “distance-to-target” approach that considered multiple objectives related to the purities and recovery of both gases. The results demonstrated that the ionic liquid–chitosan composite membranes improved the performance of other innovative membranes, with purity and recovery percentage values of 86 and 95%, respectively, for CO2 in the permeate stream, and 97 and 92% for CH4 in the retentate stream. The developed multiobjective optimization allowed for the determination of the optimal process design and performance parameters, such as the membrane area, pressure ratio and stage cut required to achieve maximum values for component separation in terms of purity and recovery. Since the purities and recoveries obtained were not enough to fulfill the requirements imposed on CO2 and CH4 streams to be directly valorized, the design of more complex multi-stage separation systems was also proposed by the application of this optimization methodology, which is considered as a useful tool to advance the implementation of the membrane separation processes. This work was funded by the Spanish Ministry of Science and Innovation Project PID2019-108136RB-C31/AEI/10.13039/501100011033. MCIN/AEI/10.13039/501100011033 and the “European Union NextGeneration EU/PRTR” are also thanked for the Grant EIN2020-112319/AEI/10.13039/501100011033.

Post-combustion processes based on ionic liquids (ILs) and membrane contactors are attractive alternatives to traditional systems. Here, a gas stream composed of 15% CO2 and 85% N2 flowed through the lumen side of a hollow-fiber membrane contactor containing poly(vinylidene fluoride)-IL (PVDF-IL) fibers. The IL 1-ethyl-3-methylimidazolium acetate [emim][Ac] served as an absorbent due to its high chemical absorption and CO2 solubility. The overall mass transfer coefficient (Koverall), activation energy (Ea), and resistances of the hollow-fiber membrane were quantified. The Koverall value was one order of magnitude higher than those reported in previous works with conventional solvents, and the Ea was lower than formerly stated values for other solvents. A theoretical simulation was conducted to estimate the operational parameters required for 90% CO2 capture and to quantify intensification effects related to CO2 absorption in a packed column. This research was funded by the Spanish Ministry of Economy and Competitiveness (Projects CTQ2013-48280-C3-1-R and CTQ2016-76231-C2-1-R). The authors thank Dr. J. C. Remigy (Laboratoire de Genie Chimique, UPS, Toulouse, France) for the preparation of 1AQ2-PVDF fibers.

CO2 emissions have to be controlled and reduced in order to avoid greenhouse effect. This work reports an analysis of the efficiency of CO2 separation using a hollow fiber membrane contactor and an ionic liquid. This process configuration contributes to the process intensification approach in the field of CO2 capture and storage. In this study, the ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim][Ac], was used as absorbent due to its high CO2 solubility. The module selected was polysulfone (Ps) because it is a well characterized polymer that allows to operate at moderate temperatures. Results were compared to previous studies with a polypropylene module. The gas stream flowed through the inside of the hollow fibers. The CO2 removal efficiency was obtained from experimental data, showing a temperature dependence: from 30 to 45.0%, corresponding to 291 K and 348 K respectively, when the Ps contactor was used. The overall mass transfer coefficient Koverall has also been evaluated. In addition, a numerical analysis was carried out to study the performance of the membrane contactor for the CO2 capture in order to estimate the process conditions to accomplish 90% CO2 capture as a target to be competitive with the conventional absorption process. This research has been funded by the Spanish Ministry Economy and Competitiveness (Project CTQ2013-48280-C3-1-R).

Hollow fiber membrane contactors with ionic liquids are promising alternatives to traditional spray towers and amines for carbon dioxide absorption. Ionic liquids have emerged as new alternative solvents because of their zero emission features compared with amines. The aim of this work was to compare fibers based on PVDF and different additives, as well as fibers including two different ionic liquids. On the one hand, 1-ethyl-3-methylimidazolium ethyl sulfate [emim][EtSO4] presents physical absorption, and on the other hand, 1-ethyl-3-methylimidazolium acetate [emim][Ac] presents chemical absorption. To compare the fibers under study, the thickness of the composite fiber was examined using scanning electron microscopy (SEM). The mechanical properties and the bubble point were also evaluated. Permeability tests were conducted, and the gas permeation of the composite hollow fibers was measured using pure CO2. Laboratory-made stainless steel modules were used for the tests. All of the above tests were performed with the fibers in both wet and dry conditions. It was determined that the fibers with the ionic liquid immobilized would be promising for CO2 capture because the CO2 permeance significantly increased. Namely, D+[emim][EtSO4] achieved a 43% increase compared with the fibers without the addition of the ionic liquid, resulting in a CO2 permeance value of 57040NL/(hm2bar), which is higher than the values reported in the literature for PVDF. Moreover, the overall mass transfer coefficient for CO2 capture using the D+[emim][Ac] fibers also presented highly competitive values. This research has been funded by the Spanish Ministry Economy and Competitiveness (Projects ENE2010-14828 and CTQ2013-48280-C3-1-R).

A bibliometric analysis based on the Web of Science database was carried out to identify the global research related to arsenic in the drinking water field from 1992 to 2012 and to improve the understanding of the research trends in the same period. The results from the analysis reveal a linearly increasing number of annual publications and a high effort to find effective technical solutions to the problems caused by the presence of arsenic in water. The most relevant research aspects of the four main technologies applied to arsenic removal from drinking water (coagulation, flocculation and precipitation followed by filtration; adsorption and ion exchange; membrane-based processes and biological treatments) were summarized in this paper, with adsorption appearing to be the alternative that has received most attention according to the research trends during the studied period.

BACKGROUND The catalytic direct synthesis of hydrogen peroxide is a highly interesting alternative process to avoid the current anthraquinone route because it implies significant sustainability improvements. Among all the peroxide applications, its use as an electronic chemical requires very low metallic content. The employment of direct synthesis peroxide as raw material for the ultrapurification process has not been investigated before, so its viability is still pending evaluation. RESULTS Although the improvements of catalyst or reactor performance of the direct synthesis process were not defined as objectives of the work, a maximum peroxide concentration of 2.3% was obtained, which is a very good result considering the low pressure used. Some relationships between the measured metallic concentrations in the obtained chemical and the operating conditions have been very useful to identify the most important conditions (selection of appropriate quality chemicals and proper materials for the installation) to promote the production of hydrogen peroxide with low metallic content. The technical competitiveness of this alternative ultrapurification process was clearly demonstrated as the number of required membrane stages (from 1 to 6 depending on the product quality) is lower than that required by the traditional case. Besides, the process can be considered economically viable if the direct synthesis peroxide can be produced with a total cost below 36.5 $ m−3. CONCLUSION Further investigation, specifically focused on holistic approaches, is still necessary in order to assess the total costs of hydrogen peroxide production by direct synthesis. This way, the current available information could be complemented and the competitiveness of this direct route to obtain hydrogen peroxide for electronic grade chemical production could be more clearly defined. © 2015 Society of Chemical Industry

Arsenic is one of the most serious inorganic contaminants in drinking water on a worldwide scale. To comply with the MCL (maximum contaminant level, 10 μg/l arsenic in drinking water) established by the World Health Organization, numerous techniques have been studied, such as ion exchange, coagulation and flocculation, precipitation, adsorption and membrane technologies. Among the available technologies applicable to water treatment, membrane filtration has been identified as a promising technology to remove arsenic from water. The goal of this study is to demonstrate the technical and economic viability of removing arsenic (V) using an optimized reverse osmosis process, with minimization of the total cost as the objective of the optimization strategy. The optimization results showed that the total costs of a two-stage membrane cascade used for the removal of arsenic (V) from drinking water for a population of 20,000 inhabitants were 1041 $/d and 0.52 $/m3 of drinking water produced. Energy consumption was the most relevant cost, corresponding to 35% of the total cost. Sensitivity analysis was performed to determine the total costs of the installation for different scenarios in terms of drinking water production: (i) 0.44–0.56 $/m3 for electricity prices of 0.05–0.10 $/KW h; (ii) 0.88–0.45 $/m3 for populations ranging from 5000 to 50,000 inhabitants; and (iii) 0.52–0.61 $/m3 when the membrane lifetime was reduced from 3 to 1.5 years. The multiobjective optimization solutions, which consider the best compromises among the quality and cost objectives, indicated that the concentration of As (V) in the permeate water can be reduced to 0.5 μg/l at a feasible cost.

Lignin valorization is a key aspect to design sustainable management systems for lignocellulosic biomass. The successful implementation of bio-refineries requires high value added applications for the chemicals derived from lignin. Without effective separation processes, the achievement of this purpose is difficult. Supported ionic liquid membranes can play a relevant role in the separation and purification of lignocellulosic components. This work investigated different supported ionic liquid membranes for selective transport of two different types of technical lignins (Kraft lignin and lignosulphonate) and monosaccharides (xylose and glucose) in aqueous solution. Although five different membrane supports and nine ionic liquids were tested, only the system composed by [BMIM][DBP] as an ionic liquid and polytetrafluoroethylene (PTFE) as a membrane support allowed the selective transport of the tested solutes. The results obtained with this selective membrane demonstrated that lignins were more slowly transferred from the feed compartment to the stripping compartment through the membrane than the monosaccharides. A model was proposed to calculate the effective mass transfer constants of the solutes through the membrane (values in the range 0.5&ndash, 2.0 &times, 10&minus, 3 m/h). Nevertheless, the stability of this identified selective membrane and its potential to be implemented in effective separation processes must be further analyzed.

The present work is focused on three main aims. The first one is the comparison of commercial polyamide (BE from Woongjin Chemical) and cellulose acetate (CE from GE Osmonics) reverse osmosis membranes when applied to the ultrapurification of aqueous hydrogen peroxide solutions. The second one is the search for possible advantages of combination of both types of membranes, which show quite different characteristics, under a hybrid cascade configuration. The results demonstrated that the employment of only polyamide membrane cascades is more competitive than hybrid systems for this application. The third one is the analysis of the influence of the product quality over the optimal economic cascades. The polyamide membrane systems were then formulated adding product quality metrics to economic criteria to afford a bicriteria nonlinear programming (NLP) problem. The Pareto solutions to the multiobjective problem were generated via the epsilon constraint method. On the one hand, maximum economic profit solutio...

A bibliometric analysis based on Scopus database was performed to identify the global research trends related to Supported Ionic Liquid Membranes (SILMs) during the time period from 1995 to 2015. This work tries to improve the understanding of the most relevant research topics and applications. The results from the analysis reveal that only after 2005 the research efforts focused on SILMs became significant, since the references found before that year are scarce. The most important research works on the four main application groups for SILMs defined in this work (carbon dioxide separation, other gas phase separations, pervaporation and liquid phase separations) were summarized in this paper. Carbon dioxide separation appeared as the application that has received by far the most attention according to the research trends during the analysed period. Comments about other significant applications that are gaining attention, such as the employment of SILMs in analytical tasks or their consideration for the production of fuel cells, have been included. This research has been financially supported by the Spanish Ministry of Economy and Competitiveness (MINECO) through CTQ2014-56820-JIN Project, co-financed by FEDER funds from European Union.

The present work is focused on the optimization of multistage reverse osmosis membrane cascades applied to the ultrapurification of chemicals for the semiconductor industry (hydrogen peroxide was chosen as case study). This paper is a part of the author`s overall work on the subject. The novelty of this paper is the introduction of a price-dependent model for the product quality that can be adjusted between customer and producer. The membrane systems were formulated with product quality-dependent price resulting a nonlinear programming problem. The optimal number of stages included in a cascade was strongly dependent of the desired product quality while the formulated quality-dependent price model determined the target purity. Five quality-dependent price fittings were used to illustrate the case study: linear, parabolic, exponential, sigmoidal, and bisigmoidal relationships between product quality and price. For the sigmoidal and bisigmoidal fittings, least operation conditions can afford revenue...

Post-combustion capture based on amines is conventionally used for carbon dioxide separation. Ionic liquids have emerged as new attractive alternative solvents because of their zero emission features compared to amines. The aim of the present work is to study the temperature influence on the efficiency in order to evaluate physical and chemical absorption using two ionic liquids, 1-Ethyl-3-methylimidazolium ethylsulfate [emim][EtSO4], and 1-Ethyl-3-methylimidazolium acetate [emim][Ac]. The temperature ranges from room temperature to 333 K. A polypropylene hollow fiber module is the membrane device where the CO2 absorption takes place. The CO2 removal efficiency was obtained from experimental data, showing a temperature dependence only in the case of using [emim][Ac] which doubles from 291 K to 318 K (16–34% for one contactor and 27–53% when two contactors were operated in series). The behavior of [emim][Ac] was correlated with the mass transfer enhanced by the chemical reaction. When [emim][EtSO4] is used, the efficiency is not influenced by the temperature and only the solubility controlled the mass transfer in the liquid phase.

The major part of the production costs of pharmaceuticals can be imputed to the downstream processing, where membrane technologies have to deal with some challenges as separations involving solutes with similar sizes or solvent recovery and recycling. This work contributes to the progress in the design of continuous organic solvent nanofiltration systems for this purpose and includes the configuration of dual membrane cascades, sensitivity analysis of the operation variables, and economic optimization as innovations. Analyzed configurations include multistage cascades up to three stages, and dual membrane cascades up to five stages. The total costs (TC) were chosen as the formulated objective function to minimize in the economic optimization strategy. The treatment of the residual stream leaving the system resulted the main cost of the process (more than 85% for dual cascades), but the solvent recovery units can significantly reduce the TC (64–77% depending on the required solvent quality). © 2014 American Institute of Chemical Engineers AIChE J, 60: 931–948, 2014

The present work is focused on the effective lifetime of reverse osmosis membranes when they are applied to the ultrapurification of aqueous hydrogen peroxide solutions, considering the very exigen...

Postcombustion processes based on membrane contactors and ionic liquids have emerged in recent years as an alternative to traditional systems used to capture CO2. In this work, nondispersive absorption in a polyvinylidene fluoride (PVDF) hollow fiber membrane contactor was used as a CO2 capture system. The ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) was chosen for the study due to its chemical reaction with CO2. Different amounts of distilled water were added to [emim][Ac] to address the issues associated with the viscosity of the ionic liquid. The presence of water may also facilitate the binding of CO2. The purpose of this combined sorbent containing water and an ionic liquid comprising a carboxylate moiety such as acetate, which provides reversible chemical interaction with CO2, was to achieve competitive efficiencies with traditional processes based on power stations and alkanolamines. The best combination of water?IL was found to be, 70% [emim][Ac]?30 vol % water. This mixture achieved a Koverall coefficient 5 times higher than that obtained with only the IL. By using 30 vol % water, a CO2 capture efficiency of 72.5% and an overall mass transfer coefficient (Koverall) of 9.34 × 10?5 m s?1 were accomplished. The values of Koverall achieved in the present work lead to the conclusion that the hybrid solvent is clearly competitive with traditional alkanolamine solvents. The simulation results of sensitivity analysis showed that only two hollow fiber membrane contactors (total length 0.6 m) or a Koverall of 1.70 × 10?4 m s?1 were required to reach an efficiency of 90%. The addition of water to the ionic liquid allows the hybrid solvent to be used in an intensified process. This research was funded by the Spanish Ministry Economy and Competitiveness (Project CTQ2013-48280-C3-1-R).

The present work proposes the design of cascades that integrate ultrafiltration (UF) and nanofiltration (NF) membranes to separate the different protein fractions from the protein hydrolysate obtained after hydrolysis of tuna byproducts. Experimental data (permeate flux and rejection of protein fractions under different applied pressures) previously obtained and published by this research group were fitted to empirical models, which were the basis for a process simulation model. High recovery rates (0.9) in the UF stages implied high process yields by reduced desired fraction losses, while similar recovery rates in the NF stages were required for high product purity. However, the applied pressures were not so influential over the performance of the system. Optimization problems were solved to identify the optimal design and operation conditions to maximize the product purity or the process yield. Maximal purity of the preferred 1-4 kDa fraction (49.3% from 19.0% in feed stream) obtained by the configuration with 3 UF stages and another 3 NF stages implied 2 and 5 bar pressures applied in the UF and NF stages, respectively, while 0.9 was the optimal recovery rate value for all the stages. These maximal purity conditions resulted in 62.6% process yield, defined as the percentage of the 1-4 kDa fraction in the feed stream recovered in the product stream. In addition, multiobjective optimization of the process was also carried out to obtain the Pareto graphs that represent the counterbalance between maximal yields and purities.

International audience; Ultrafiltration and nanofiltration can be very useful technologies to fractionate the different protein fractions obtained after hydrolysis of fish by-products. Simple empirical transport equations derived from experimental data were obtained and a process simulation model was developed and employed for the identification of the optimal design and operation conditions to maximize the product purity or the process yield. More complex scenario appeared when other objectives were added to the optimization problem, including economic considerations, such as the total costs of the process, or environmental considerations, such as the total freshwater consumption by the system. Limitations to the total costs implied reduced membrane area in the UF stages and, consequently, lower process yields. Freshwater consumption could be reduced without worsening product purity or process yield, but limits should be imposed in order to avoid excessive protein contents that would cause problems related to membrane clogging.

The chemicals and materials used to manufacture and package semiconductors and printed circuit boards are called electronic chemicals. The purity of these electronic chemicals, given by the industry association Semiconductor Equipment and Materials International (SEMI), is a very compromising concern for the semiconductor industrial sector, so very strict requirements are set to avoid microelectronic devices failures because of the content of impurities of electronic chemicals. For the particular case of hydrogen peroxide as one of the most consumed wet electronic chemicals, SEMI Document C30-1110 indicates five different electronic grades defined by their limiting impurities content. The semiconductor industry is appearing as an emerging application of reverse osmosis membranes based processes. After reviewing the patents published over the last twenty years about ultrapurification for industrial production of high purity electronic grade hydrogen peroxide, the referenced separation techniques can be replaced by reverse osmosis with lower operating expenses due to energy and chemicals. This work proposes a membrane process design based on an integrated countercurrent membrane cascade, in order to determine the optimum osmosis cascade for each SEMI Grade hydrogen peroxide, with the economic profit as the objective function in the optimization strategy. The results show the benefits of the reverse osmosis process, with profit values of 20–85 million $/year, for a target annual production of 9000 tons of electronic hydrogen peroxide, requiring the integrated reverse osmosis cascades of two stages for the production of Grade 1 to seven stages for the strictest Grade 5.

Very high purity chemicals are required for preparation of semiconductor materials and manufacture of printed circuit boards because low presence of metallic impurities is needed to avoid defects on silicon surface. Hydrogen peroxide is one of the most demanded chemical by the semiconductor industry and it must be submitted to ultrapurification processes to achieve the exigent requirements the chemical must fulfill to be accepted for semiconductor uses. In this paper, the potential of multistage reverse osmosis processes to reduce the metallic content of technical grade hydrogen peroxide below the limits fixed by the semiconductor industry is investigated. SEMI Grade 1 quality hydrogen peroxide was obtained by a two-pass reverse osmosis process in an experimental lab scale. A model based on Kedem-Katchalsky transport equations together with system material balances was proposed to describe the behavior of the installation. A full analysis of the influence of the design (recovery rates) and operation (applied pressures) variables over the performance of a simulated industrial scale plant was carried out. The economic viability of the simulated plant was demonstrated.

This work is focused on the optimization of a reverse osmosis network proposed for the ultrapurification of chemicals, from technical grade to semiconductor grades demanded in electronic applications that require the use of high-purity wet chemicals in the semiconductor manufacturing, as it is the case of hydrogen peroxide that is commonly used in the wafer cleaning and surface conditioning processes. An industrial installation able to produce simultaneously the five different Semiconductor Equipment and Materials International Grades of hydrogen peroxide is represented by a simplified superstructure configuration formulated as a nonlinear programming problem. The network integrates reverse osmosis membrane modules, mixers, and split functions, defined by the equations of mass balances and the Kedem–Katchalsky transport model for the description of the permeate flux and the metal rejection coefficients at each membrane stage. The objective of the design is to maximize the daily profit obtained from the sale of the electronic grades of hydrogen peroxide produced by the ultrapurification system. V C 2012 American Institute of Chemical Engineers AIChE J, 58: 3718‐3730, 2012

Recovery of sulfur dioxide from gas emissions using a membrane device instead of technology based on dispersive absorption (e.g. scrubbers) is considered as an alternative to reduce environmental impacts and costs associated to solvent losses. The technical viability has been demonstrated in the recent literature but an economic estimation has to be performed in order to evaluate the application of these processes in an industrial scale. This work considers a ceramic hollow fibre membrane contactor as membrane device to recover sulfur dioxide from gas streams. In addition to the technical considerations, environmental and economic issues are discussed in order to include these aspects in the decision making for industrial application. The economic estimation is carried out in terms of investment and operating costs and it is observed that the industrial application is strongly dependent on the environmental restrictions and the concentration of sulfur dioxide at the inlet of the membrane device.

The present research is centred upon the application of reverse osmosis to the ultrapurification of aqueous hydrogen peroxide (35%, w/w). Semiconductor Equipment and Materials International (SEMI) organization develops the globally most respected standards to establish the quality requirements for the chemicals used in this sector; one of these standards, SEMI C30 is proposed for hydrogen peroxide. Electronic grade hydrogen peroxide accounts for sub-ppm metallic impurity levels (sub-ppb concentrations are required for the most exigent grades), so various elements present as impurities in technical grade hydrogen peroxide exceed the fixed limits. A preliminary experimental study was carried out with a laboratory-scale facility (flat-sheet membrane unit) with 6 different commercial reverse osmosis membranes in order to choose the most appropriate one for hydrogen peroxide ultrapurification. BE membrane (manufactured by Woongjin Chemical) was selected for further viability study because of its higher permeate flux (1.95 × 10−5 m3/m2 s at 40 bar) and metal rejections values (ranging from 0.825 for B to 0.961 for Cu). The Kedem–Katchalsky model resulted as the most representative for characterizing the selected membrane behaviour as it achieved a percentage of overall variation explained upper than 94%.

Many ionic liquids are soluble in water and their impact on the aquatic environment has to be evaluated. However, due to the large number of ionic liquids and the lack of experimental data, it is necessary to develop estimation procedures in order to reduce the materials and time consumption. Quantitative structure–activity relationships (QSARs) are models that can be used to estimate the physicochemical and toxicological properties of molecules from the molecular structure or properties of similar compounds whose activities have already been assessed. In this work, a novel QSAR based on multiple linear regression is applied in order to estimate the ecotoxicity of ionic liquids, expressed as EC50 (Vibrio fischeri), involving 9 kind of cations and 17 anions. The range of log EC50 values covered by the novel QSAR is from -0.23 to 5.00. From the results, the influence of cations, anions and substitutions on the ecotoxicity of ionic liquids is established.

This work focuses on fluoride recovery as a solid product CaF2 in order to (i) improve process efficiency by means of the reduction of fines formation with the distributed feeding of calcium along the height of the reactor when high fluoride concentrations have to be treated; and (ii) to correlate the supersaturation effect on the fines formation and the process efficiency for the fluoride recovery as synthetic calcium fluoride. An estimation of two parameters related to the product growth and the fines formation equations was performed in order to predict the process efficiencies in terms of fluoride removal and recovery as a solid product. The process simulation also provided the description of the crystallization process carried out in the tubular reactor contributing to the design and operation purposes for industrial applications of the fluoride control with recovery of solid product recovery as synthetic CaF2 in pellet form available for industrial use.

Sulfur dioxide (SO2) and carbon dioxide (CO2) emissions have to be efficiently controlled due to environmental, economic and social demands. An interesting approach for SO2 and CO2 separation/concentration is the use of supported ionic liquid membranes (SILMs). Ionic liquids (ILs) are very interesting compounds for this application since they have a negligible vapour pressure, leading to high stability and reducing solvent losses by volatilization to the gas stream. pIn this work, the permeabilities of air, CO2 and 10 vol.% SO2–air have been obtained using different SILMs. The permeability of air is one order of magnitude lower than CO2 permeability and it is also lower than the permeability of the mixture of air and 10 vol.% SO2. In addition, the selectivities of CO2 and the SO2 mixture have been obtained.

Selective absorption into a liquid is a widespread method to separate and concentrate sulfur dioxide from gas emissions, reducing air pollution and environmental risks. Process intensification can be performed first by the substitution of the equipment (e.g. scrubbers) for a membrane device to avoid drops dragging, and second by the substitution of the absorption solvent (e.g. N,N-dimethylaniline) for ionic liquids to avoid solvent volatilization. According to this intensification, a zero solvent emission process has been developed. The ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is used as the absorption solvent and the results are compared to the N,N-dimethylaniline results. A ceramic hollow fibre module is the membrane device where the sulfur dioxide absorption takes place. A gas stream with a typical composition of roasting effluents flows through the shell side and the absorption liquid flows counter currently by the inside of the hollow fibres. The influence of carbon dioxide in the absorption is also evaluated and the overall mass transfer coefficients are calculated. The difference between the estimated mass transfer coefficients and the experimental results for both solvents is discussed assuming partial wetting of the membrane.

BACKGROUND: Removal of sulfur dioxide from gas emissions by selective absorption is a common method to separate and concentrate sulfur dioxide and to reduce air pollution and environmental risks. N,N-dimethylaniline is an organic solvent used in some industrial applications for its sulfur dioxide affinity, leading to a regenerative process. However, the use of scrubbers and equipment in which direct contact between gas and liquid takes place leads to solvent losses due to evaporation and drops dragging. RESULTS: In this work, an innovative procedure based on non-dispersive absorption in a ceramic hollow fibre membrane contactor was studied in order to avoid drops dragging. The absorption efficiency ranged between 40 and 50%, showing the technical viability of the process. The sulfur dioxide flux through the membrane has a linear relationship with the concentration of SO2 in the gas stream and an overall mass transfer coefficient Koverall = (1.10 ± 0.11) × 10 −5 ms −1 has been obtained. CONCLUSIONS: The mass transfer behaviour of a ceramic hollow fibre membrane contactor for sulfur dioxide non-dispersive absorption in N,N-dimethylaniline has been studied. The main resistance is found to be the ceramic membrane and the effective diffusivity has been inferred. The mass transfer model and parameters allow the evaluation of equipment design for technical applications.  2008 Society of Chemical Industry

Crystallization process in a fluidized bed reactor (FBR) appears as an alternative clean technology to the conventional chemical precipitation process. Crystallization process in a FBR contributes to an environmental friendly production, because it allows reducing the waste production as well as recovery of materials. The aim of this work is to scale up the crystallization process in a FBR for the treatment of industrial fluoride wastewater. The technical viability of the process was concluded in agreement with the obtained results in laboratory scale, with fluoride recovery efficiencies in the reactor between 70 and 80% to form synthetic CaF2, which is able to be recycled as raw material for the production of hydrofluoric acid.

Crystallization process in a fluidized bed reactor to remove fluoride from industrial wastewaters has been studied as a suitable alternative to the chemical precipitation, which generates large amounts of a water rich sludge that must be disposed of with increasing costs. The major advantage of this technology is the decrease of sludge formation, the simplification of the materials recovery procedures and the reduction of solid wastes. Removal of fluoride by crystallization process has been carried out in a laboratory-scale fluidized bed reactor focused to the analysis of the influence of the supersaturation (S), the up-flow velocity (SV) and the amount and mean diameter of seed material (L0) on the process efficiency, which are related to the crystal growth. In the modeling, design and control of a fluidized bed reactor for water treatment it is necessary to study the particle growth kinetics. From the results obtained in this study, it has been proposed a growth model represented by the equation G = 2.96 × 10 − 5 L 0 1.37 S V 0.5 S ( m s − 1 ) , which fits well the experimental data in the interval of variables studied.

Crystallization process in a fluidized bed reactor to remove fluoride from industrial wastewaters has been studied as a suitable alternative to the chemical precipitation in order to decrease the sludge formation as well as to recover fluoride as synthetic calcium fluoride. In the modeling, design and control of a fluidized bed reactor for water treatment it is necessary to study the particle growth kinetics. Removal of fluoride by crystallization process in a fluidized bed reactor using granular calcite as seed material has been carried out in a laboratory-scale fluidized bed reactor in order to study the particle growth kinetics for modeling, design, control and operation purposes. The main variables have been studied, including superficial velocity ( SV , m s - 1 ), particle size of the seed material ( L 0 , m) and supersaturation ( S ). It has been developed a growth model based on the aggregation and molecular growth mechanisms. The kinetic model and parameters given by the equation G = ( 2.26 × 10 - 10 + 2.82 × 10 - 3 L 0 2 ) SV 0.5 S fits well the experimental data for the studied range of variables.

The removal of fluoride in a fluidized bed reactor by crystallization on the surface of sand grains has been studied as an alternative to chemical precipitation, which generates huge amounts of a water rich sludge that is not possible to recover due to the high water content and the low quality of the sludge. Water recycling is required in order to decrease the fluoride concentration and prevent primary nucleation. However, water recycling may increase the secondary nucleation and, therefore, the efficiency of the process is lower due to the formation of fines, which cannot be recovered. The environmental benefits of the reuse of raw materials and the reduction of wastewater make it necessary to improve the efficiency of the process, reducing the formation of fines. The influence of supersaturation has been experimentally studied, leading to a quantitative model. The combination of a fluidized bed reactor and a sand filter bed in the process has been able to achieve a reduction in the formation of fines f...

The prediction of the SO 2 removal efficiency achieved in the in-duct desulfurization process at low temperatures was performed from data obtained in an entrained flow reactor at pilot scale. It was used a synthetic flue gas stream with the typical composition of the coal–power plants, and the solid sorbent was commercial Ca(OH) 2 . The variables included in the experimental study were calcium to sulfur molar ratio, SO 2 inlet concentration, temperature, relative humidity, CO 2 content in the gas stream, and residence time in the flow reactor. The experimental facility provided the evaluation of SO 2 concentration along the reactor up to 4 s of residence time. Two different approaches to model were used for the evaluation of the process behaviour: a mechanistical approach from the basis of the shrinking core and the grain models, and a statistical non-linear approach using neural network analysis.