Membrane Technology applied, among others, in processes such as Ultrafiltration (UF) and Nanofiltration (NF), has become an important part of biotechnological separation processes in recent decades. Its main feature, the morphology of the porous filters, leading to a “sieving mechanism” allows effective separation with high selectivity features and made in energy and environmental conditions very interesting.
Given the enormous development of membrane filters, it becomes necessary the growth in parallel of characterization techniques applied to such filters, as essential tools for both manufacturers and end-users or researchers.
In this sense we need to know most exactly possible, both functional and structural parameters of the membrane, all necessary for a proper choice of that with a view to a particular application.
The question we must face is: Is there a characterization method, by itself, giving us a clear and easily interpretable picture of the true structure and functionality of the filter?.
The answer to this question is obviously no. There are so many structural and functional parameters that contribute to the exact knowledge of the membrane, that there is no technique that can bring us all this wealth of information.
From the industrial and commercial standpoints, the parameter most used and required, in view of possible applications of the filters, it is the molecular weight cut-off (MWCO), although it is clear that by itself is not a definitive tool for choosing a membrane filter.
SMAP® group long experience in membrane characterization allows us to conclude that porosimetric techniques give interesting information related to the size and size distribution of the pores present in a membrane, information that can be conveniently checked against functional aspects of it.
In this sense, we can consider that Liquid-liquid displacement porosimetry (LLDP) is the most promising porosimetric technique in the range of Ultrafiltration, thus giving us important information about these filters.
Contents
RESUMEN / ABSTRACT
ORGANIZACIÓN DE LA MEMORIA / THESIS OUTLINE
OBJETIVOS / SCOPES
1 OVERVIEW OF MEMBRANE SCIENCE AND TECHNOLOGY
1.1 INTRODUCTION
1.2 MEMBRANE MARKET
1.3 FUNDAMENTALS OF MEMBRANES
1.3.1 Definition and Classification
1.3.2 Membrane Module Design
1.3.3 Membrane Material
1.4 MEMBRANE PROCESSES
1.4.1 Pressure Driven Membrane Processes
1.4.2 Concentration Gradient Driven Processes
1.4.3 Electrical Potential Driven Membrane Processes
1.4.4 Temperature Gradient Driven Membrane Processes
1.5 CHARACTERIZATION OF MEMBRANES
1.5.1CharacterizationMethods
1.5.2 Methods of Liquid Penetration
1.5.2.1 Fundamentals
1.5.2.2 Bubble Point Method
1.5.2.3 Fluid Displacement -Air Liquid Displacement -Liquid-Liquid Displacement
1.6 CONCLUSIONS
1.7 REFERENCES
2 DEVELOPMENT AND OPTIMIZATION OF A LIQUID-LIQUID DISPLACEMENT POROMETER DEVICE
2.1 HISTORICAL
2.2 LLDP ANALYSIS FUNDAMENTALS
2.2.1 Grabar-Nikitine Algorithm
2.3 AUTOMATED LLDP POROSIMETER
2.3.1LLDP Setup
2.3.2 Porosimetric Liquids Preparation
2.3.3 LLDP Analysis
2.3.4 Data Analysis and Treatment
2.4 CONCLUSIONS
2.5 REFERENCES
7 CONCLUSIONES / CONCLUSIONS
AGRADECIMIENTOS
Al finalizar un trabajo tan arduo y lleno de dificultades como el desarrollo de una tesis doctoral es inevitable padecer un muy humano egocentrismo que te lleva a concentrar la mayor parte del mérito en el aporte que has realizado, pero en cambio si lo analizamos objetivamente te demuestras inmediatamente que la magnitud de este aporte hubiese sido imposible sin la participación de muchas personas e instituciones que han facilitado mi evolución para que este trabajo llegue a un feliz término. Por ello, es para mí un verdadero placer utilizar este espacio para ser justo y consecuente con todos ellos, expresándoles mis agradecimientos.
Debo agradecer de manera especial y sincera a mi director de tesis el Dr José Ignacio Calvo Diez, por haberme dado la oportunidad de aceptarme bajo su dirección. Su apoyo y confianza en mi trabajo y su capacidad para guiar mis ideas, ha sido un ayuda incalculable, no solamente en el desarrollo de este trabajo, sino también en mi formación como investigador. Orientación, flexibilidad y rigurosidad en el campo científico, han sido clave del buen trabajo que hemos realizado juntos, el cual no se puede concebir sin su siempre oportuna participación, agradeciéndole en todo momento el haberme facilitado siempre los medios suficientes para llevar a cabo todas las actividades propuestas durante el desarrollo de esta tesis.
Quisiera extender también este agradecimiento a los Dres Antonio Hernández Giménez, Laura Palacio Martínez y Pedro Prádanos del Pico, todos ellos “cabezas” indiscutibles del SMAP® y docentes de la Universidad de Valladolid, con quienes he compartido estos buenos años de trabajo y quienes han estado a mi lado en todo momento.
A todos mis “colegas” de laboratorio, a los que siguen y a los que ya no están, lesy
doy las gracias por haberme apoyado y hecho pasar excelentes momentos: Alberto, Alvaro, Andrea, Blanca, Fernando, Gloria, Liliana, Miguel, Noemí, Raquel, Roberto, Sara, Youssef.
Mis más sinceros agradecimientos a todo el personal del departamento de Física Aplicada, José Carlos, Isaías, Felipe y, en especial a Isma, agradecerles sinceramente su apoyo.
También quiero agradecer este trabajo a Juan Marcos Sánz Casado, compañero de estudios y exponente fundamental de esta técnica, dejándome un impresionante legado, siendo el hilo conductor en su implementación y desarrollo, junto a Pablo y Valeriano en las arduas tareas de programación.
Me gustaría además expresar mi gratitud a todo los tutores responsables, personal técnico, profesores, estudiantes y compañeros en mis estancias “fuera de casa” entre ellos al grupo de biorreactores encabezado por los doctores Emilia Ma Guadix Escobar y Antonio Ma Guadix del Departamento de Ingeniería Química de la Universidad de Granada, y en especial a Mari Carmén Almécija, compañera de trabajo en diferentes estancias, así como en lo personal.
A mis compañeros de laboratorio de investigación y desarrollo, en mi estancia en Sartorius Stedim Biotech® en Göttingen, entre ellos, Celia, Pedro, Tobias, Jan, Roberto, Verónica,...
A los miembros del Departamento de Química y Química Industrial de la Universidad de Génova, entre los que destaco afectuosamente a Giorgio, Antonio Comite, Silvia, Rafaella por su cálida acogida y especialmente a los Profesores Capanelli y Bottino, por su infinita ayuda, profesionalidad y experiencia en esta técnica, siendo ellos los auténticos pioneros en este campo.
Grazie mile con tutto il cuore
I would like to acknowledge Dr. Volkmar Thom and Kuong To-Vinh, from the R&D Departament of Sartorius-Stedim Biotech®, at Göttingen, for the opportunity they gave me to introduce in research through a collaboration with them, and for the kindness they offered me, which I would never forget.
Ich danke Ihnen sehr
A los miembros del servicio de imprenta y publicaciones de la Universidad de León, en especial a Tomás.
Para todos aquellos que omito por falta de memoria, sin intención de restarles importancia, les agradezco enormemente su apoyo también.
Por último, quiero agradecer a todos mis amigos, que me han brindado su cariñoy y comprensión en todo momento, siempre atentos a mi evolución, Angel, Héctor, Gabi, Rubén, Luis Carlos, Fernan, Patri, Jaime, Guty, Reke y por supuesto a toda mi familia, quienes me han apoyado con cualquier decisión que he tomado y quienes continuamente me animan a continuar en este intenso, pero apasionante camino de la investigación científica.
Acknowledgements
Sartorius-Stedim Biotech® is acknowledged for funding through contract 061/074251 with the Fundación General de la Universidad de Valladolid, including a grant for the author during the period of the experimental work of this thesis.
Universidad de Valladolid, through its program “Ayudas para estancias breves en el desarrollo de tesis doctorales” is acknowledged for the funding of visits to the labs of Sartorius (Göttingen, Germany), Universidad de Génova (Italia) and Universidad de Granada (España.
RESUMEN
La tecnología de membranas aplicada, entre otros, en procesos como la Ultrafiltra- ción (UF) y la Nanofiltración (NF), se ha convertido en una importante parte de los procesos biotecnológicos de separación en los últimos decenios. Su principal característica, la morfología porosa de los filtros, conducente a un “mecanismo de criba”, permite una separación efectiva con altas características de selectividad y realizada en condiciones medioambientales y energéticas muy interesantes.
Ante el desarrollo ingente de los filtros de membrana, se hace necesario un crecimiento en paralelo de las técnicas de caracterización de dicho filtros, como herramientas fundamentales tanto para fabricantes, como usuarios o investigadores.
En este sentido necesitamos conocer de primera mano tanto los parámetros funcionales como los estructurales de la membrana, necesarios para una adecuada elección de la misma con vistas a una determinada aplicación.
La cuestión que se nos plantea es la siguiente: ¿Existe algún método de caracterización que, por sí sólo, nos de una visión clara y fácilmente interpretable de la verdadera estructura y funcionalidad del filtro?.
La respuesta a esta pregunta, evidentemente, es nula. Son tantos los parámetros estructurales y funcionales que contribuyen al conocimiento exacto de la membrana, que no hay ninguna técnica que pueda aportarnos toda esta cantidad de información.
Desde el punto de vista industrial y comercial, el parámetro más utilizado y requerido, con vistas a posibles aplicaciones de los filtros, es el peso molecular de corte (MWCO), aunque es evidente que por sí sólo no constituye una herramienta definitiva para la elección de un filtro de membrana.
La larga experiencia del SMAP® en caracterización de membranas nos permite concluir que las técnicas porosimétricas dan información muy interesante, relacionada con el tamaño y la distribución de tamaños presentes en una membrana, información que puede ser convenientemente cotejada con aspectos funcionales de la misma.
En ese sentido, la técnica porosimétrica que podemos considerar más prometedora y completa en el rango de Ultrafiltración, es la Porosimetría de Desplazamiento Líquido- líquido (LLDP), la cual nos da información muy importante sobre este tipo de filtros.
Ahora bien, varios problemas se plantean en cuanto a la mejor aplicación de la técnica LLDP:
a) mejorar las condiciones operativas de la técnica, considerada por muchos investigadores como poco reproducible y complicada desde el punto de vista operativo.
b) extender el rango de aplicación de dicha técnica a membranas de Nanofiltración, en las que los poros existentes van a estar en el rango cercano al nanómetro.
c) relacionar la información estructural obtenida con datos funcionales, especialmente con el MWCO, a fin de utilizar la técnica LLDP para estimar la aplicabilidad de una membrana a un proceso de separación dado.
A la mejora de estas cuestiones pretende contribuir la tesis presentada, mediante la mejora de la técnica LLDP, automatizando el equipo LLDP desarrollado en el SMAP®, optimizando su forma de trabajo y operación y finalmente, extendiendo al máximo su rango de trabajo, a fin de que pueda cubrir tanto el rango de UF como buena parte de las membranas comerciales de NF.
Finalmente se ha buscado correlacionar la información estructural obtenida con el MWCO de las membranas analizadas, de forma que podamos asegurar una fiable estimación de las prestaciones operativas de las membranas en procesos industriales.
ABSTRACT
Membrane Technology applied, among others, in processes such as Ultrafiltration (UF) and Nanofiltration (NF), has become an important part of biotechnological separation processes in recent decades. Its main feature, the morphology of the porous filters, leading to a “sieving mechanism” allows effective separation with high selectivity features and made in energy and environmental conditions very interesting.
Given the enormous development of membrane filters, it becomes necessary the growth in parallel of characterization techniques applied to such filters, as essential tools for both manufacturers and end-users or researchers.
In this sense we need to know most exactly possible, both functional and structural parameters of the membrane, all necessary for a proper choice of that with a view to a particular application.
The question we must face is: Is there a characterization method, by itself, giving us a clear and easily interpretable picture of the true structure and functionality of the filter?.
The answer to this question is obviously no. There are so many structural and functional parameters that contribute to the exact knowledge of the membrane, that there is no technique that can bring us all this wealth of information.
From the industrial and commercial standpoints, the parameter most used and required, in view of possible applications of the filters, it is the molecular weight cut-off (MWCO), although it is clear that by itself is not a definitive tool for choosing a membrane filter.
SMAP® group long experience in membrane characterization allows us to conclude that porosimetric techniques give interesting information related to the size and size distribution of the pores present in a membrane, information that can be conveniently checked against functional aspects of it.
In this sense, we can consider that Liquid-liquid displacement porosimetry (LLDP) is the most promising porosimetric technique in the range of Ultrafiltration, thus giving us important information about these filters.
However, several problems arise regarding the best application of the LLDP technique:
a) improvement of the operating conditions of the technique, considered by many researchers to be poorly reproducible and difficult from the standpoint of operating,
b) extension of the application range of this technique to Nanofiltration membranes, in which the pores are mostly in the range close to nanometer,
c) connection of the structural information obtained with functional data, especially with the MWCO, to use the LLDP technique for estimating applicability of a membrane to a given separation process.
To improve these issues, the present thesis aims to contribute by improving the LLDP technique, automating the LLDP equipment developed in the SMAP®, optimizing the way they work and operates, and finally, extending at the maximum the working range, so that it can cover both the range of UF and most of commercial NF membranes.
Finally it has been sought to correlate structural information obtained from tested membranes, with their MWCO, so that we can ensure a reliable estimate of the operating performance of the membranes in industrial processes.
ORGANIZACIÓN DE LA MEMORIA
De acuerdo con la normativa vigente (Ejecución de Acuerdos de la Comisión de Doctorado de la Universidad de Valladolid de fecha 10 de mayo de 2010), esta Tesis Doctoral se presenta como compendio de publicaciones.
Además de incluir los diversos artículos publicados (Capítulos 3-6) como consecuencia del trabajo doctoral, se introduce mediante una síntesis de los conceptos téorico- experimentales mediante una extensa revisión (“state of the art”) de las membranas, los procesos de membranas y las diversas técnicas de caracterización, con especial atención a la técnica de desplazamiento líquido-líquido (capítulo 2). Ambos capítulos introductorios permiten situar y enmarcar los contenidos de los artículos publicados en relación con los objetivos generales perseguidos al comienzo de esta tesis.
Los trabajos incluidos en este documento son los siguientes:
1. Characterization of UF membranes by liquid-liquid displacement porosimetry. J.M. Sanz, R. Peinador, J.I. Calvo, A. Hernández, A.Bottino, G. Capannelli. Desalination, 245 (2009) 546-553.
2. Characterisation of polymeric UF membranes by liquid-liquid displacement po- rosimetry.
René Israel Peinador, José Ignacio Calvo, Pedro Prádanos, Laura Palacio, Antonio Hernández.
Journal ofMembrane Science, 348 (2010) 238-244.
3. Liquid-liquid displacement porosimetry for the characterization of virus retentive membranes.
René Israel Peinador, José Ignacio Calvo, Khuong ToVinh, Volkmar Thom, Pedro Prádanos and Antonio Hernández.
Journal ofMembrane Science, 372 (2011) 366-372.
4. Liquid-liquid displacement porometry to estimate the molecular weight cut-off of ultrafiltration membranes.
José Ignacio Calvo, René Israel Peinador, Pedro Prádanos, Laura Palacio, Aldo Bottino, Gustavo Capannelli, Antonio Hernández.
Desalination, 268 (2011) 174-181.
No se incluyen en esta memoria aquellos trabajos o resultados que, siendo realizados en el marco de la financiación del proyecto conjunto entre el SMAP® y la empresa Sartorius-Stedim Biotech®, estén sujetos a propiedad industrial o consistan en información sensible para los competidores de dicha empresa.
THESIS OUTLINE
In accordance with current regulations (from the Doctoral Committee of the University of Valladolid, dated May 10,2010), this PhD Thesis is presented as a compendium of publications.
Besides including various published articles (Chapters 3-6) as a result of doctoral work, it is introduced by an overview ofboth theoretical and experimental concepts through an extensive review (“state of the art”) of the membranes, membrane processes and various characterization techniques (Chapter 1), with special attention to the technique of liquid-liquid displacement (Chapter 2). Both introductory chapters situate and frame the contents of the articles published in relation to the general objectives pursued at the beginning of this thesis.
The papers included in this document are:
1. Characterization of UF membranes by liquid-liquid displacement porosimetry. J.M. Sanz, R. Peinador, J.I. Calvo, A. Hernández, A.Bottino, G. Capannelli.
Desalination, 245 (2009) 546-553.
2. Characterisation of polymeric UF membranes by liquid-liquid displacement po- rosimetry.
René Israel Peinador, José Ignacio Calvo, Pedro Prádanos, Laura Palacio, Antonio Hernández.
Journal ofMembrane Science, 348 (2010) 238-244.
3. Liquid-liquid displacement porosimetry for the characterization of virus retentive membranes.
René Israel Peinador, José Ignacio Calvo, Khuong ToVinh, Volkmar Thom, Pedro Prádanos and Antonio Hernández.
Journal ofMembrane Science, 372 (2011) 366-372.
4. Liquid-liquid displacement porometry to estimate the molecular weight cut-off of ultrafiltration membranes.
José Ignacio Calvo, René Israel Peinador, Pedro Prádanos, Laura Palacio, Aldo Bottino, Gustavo Capannelli, Antonio Hernández.
Desalination, 268 (2011) 174-181.
Not included in this report are those works or results, being conducted under the joint project between SMAP® and Sartorius-Stedim Biotech®, which are subjected to industrial property or consist of sensitive information to competitors of that company.
OBJETIVOS
El objetivo principal de este trabajo experimental es la mejora de la técnica de Po- rosimetría de Desplazamiento Líquido-líquido y su mejor aplicación al análisis de filtros porosos comerciales.
Para la consecución de este objetivo, diversas líneas simultáneas y complementarias se han seguido:
a) automatización del equipo LLDP existente en el SMAP® de la Universidad de Valladolid, equipo desarrollado en cercana colaboración con los Dres. Bottino y Capannelli de la Universidad de Génova,
b) comprobación de las condiciones óptimas de trabajo de las diversas mezclas porosi- métricas, de forma que estas puedan ser convenientemente elegidas en función del rango de poros a analizar o de la interacción de dichos líquidos con las membranas estudiadas,
c) estudio teórico de la correlación entre parámetros estructurales y funcionales de los filtros de membrana, buscando conectar la información obtenida de nuestro equipo, con datos funcionales de interés en la aplicación industrial de estos filtros.
Trabajando siempre en dichas líneas, se han realizado varias etapas, que han conducido a la publicación de los diversos artículos relacionados en esta memoria. Estas etapas se pueden resumir como sigue:
1) estudio de varias membranas de UF (tanto abiertas y como de poros más cercanos a NF) y análisis de su información porosimétrica,
2) estudio de varias membranas de NF, con diversas mezclas porosimétricas, en condiciones extremas de incompatibilidad química con los líquidos habituales,
3) estudio de membranas diseñadas para la retención de virus y correlación de la información porosimétrica con información funcional obtenida por variadas técnicas,
4) elaboración de un procedimiento de estimación del peso molecular de corte en membranas de UF y NF y comprobación de su validez en un amplio rango de membranas comerciales.
Todas estas etapas, y su exitosa culminación, deberían permitirnos avanzar en lo que consideramos un objetivo primordial de este trabajo y de la línea de investigación del SMAP® que lo sustenta:
Contribuir a la extensión de la técnica LLDP aplicada a la caracterización estructural de membranas sintéticas en el rango de UF-NF, así como su posible estandarización como técnica de referencia en el estudio estructural y funcional de dichas membranas.
SCOPES
The main objective of this experimental work is the improvement of the Liquidliquid displacement porosimetry and the best application of this technique to the analysis of commercial porous filters.
To achieve this goal, various simultaneous and complementary lines have been followed:
a) automatization of existing LLDP setup, built-up in the SMAP® at the University of Valladolid, equipment developed in close collaboration with Drs. Capannelli and Bottino from the University of Genoa,
b) verification of the optimum working conditions of the various porosimetric mixtures, so that they can be suitably chosen according to the range of pores to be analyzed or the interaction of these fluids with the membranes studied,
c) theoretical study of the correlation between structural and functional parameters of the membrane filters, seeking to connect the information obtained from our setup, with functional data of interest in the industrial application of these filters.
Always working on these lines, there have been followed several steps, which led to the publication of several articles herein. These steps can be summarized as follows:
1) study of various UF membranes (both open and those with pores close to NF) and analysis of their porosimetric information,
2) study of various NF membranes by using several porosimetric mixtures, in extreme conditions of chemical incompatibility with the usual liquid pairs,
3) studying membranes designed for retention of viruses and correlation of the porosimetric information with functional information obtained by various techniques,
4) development of a procedure for estimating the molecular weight cut-off in UF and NF membranes and checking their validity in a wide range of commercial membranes.
All these stages, and its successful completion, should allow us to advance in what we consider a primary objective of this work and the research line supported in the SMAP® group:
Contribute to the extension of LLDP technique applied to the structural characterization of synthetic membranes in the range of UF-NF and their possible standardization as reference technique in structural and functional studies of these membranes.
1 OVERVIEW OF MEMBRANE SCIENCE AND TECHNOLOGY
1.1 INTRODUCTION
Membrane science and technology have seen the rationalization of production systems in the last decades. Their intrinsic characteristics of efficiency, operational simplicity and flexibility, relatively high selectivity and permeability for the transport of specific components, low energy requirements, good stability under a wide spectrum of operating conditions, environment compatibility, easy control and scale-up; have been confirmed in a large variety of applications and operations1, both in liquid and gas phases and in a wide spectrum of operating parameters such as pH, temperature, pressure, etc. The possibility of using membrane systems as well as tools for a better design of chemical reactions is becoming attractive and realistic. For biological applications, synthetic membranes provide an ideal mechanical support due to their available surface area per unit volume.
Membranes and membrane processes were first introduced as an analytical tool in chemical and biomedical laboratories; they developed very rapidly into industrial products and methods with significant technical and commercial impact[1]. Today, membranes are used on a large scale to produce potable water from sea and brackish water, to clean industrial effluents, to recover valuable constituents, to concentrate, purify, or fractionate macromolecular mixtures in food and drug industries, as well as to separate gases and vapours in petrochemical processes. Membranes are also key components in energy conversion and storage systems, in chemical reactors, artificial organs, and in drug delivery devices. The membranes used in the various applications differ widely in their structure, in their function and the way in which they operate[2], being particularly attractive tools for the separation of molecular mixtures.
1.2 MEMBRANE MARKET
Membrane filtration and separation technologies have undergone significant technological advancement in recent decades[3]. Such progress has revolutionized numerous industrial processes, biotechnology developments, as well as purification of urban water supply. Thanks to its ability to effectively separate undesirable constituents from any feed- stream with consistent product quality, Membrane. Tech has evolved into a well-accepted method of filtration in many applications[4], being most significative ones: from drinking water and wastewater treatment to seawater desalination; generation of high purity water for cooling powers and boiler feed too; separation of oil and chemicals from industrial waste-streams. Therefore, membrane filtration often plays an indispensable role, without which many of these products would not have existed.
The majority of membrane sales relate to water treatment and medical applications[5], both mainly considered as a principal tradeline. In the case of water treatment, for example, only for domestic use, total world demand has increased (see Tablel.1). about 25% from 2006 to2011.
Abbildung in dieser Leseprobe nicht enthalten
Table 1.1 Main membranes demand for domestic use in five years (US M$). Fredonian Goup[6]
Other studies report both higher and lower market size, [7-12]. In this way, membrane filtration is applicable to a broad range ofhighly specialized end user markets. The total world sales for membrane modules, are given as current year estimates and forecast for the period from 2006 to2011 in Table 1.2.
Abbildung in dieser Leseprobe nicht enthalten
Table 1.2 The World Market For Membrane Modules2 (US$ Million)
The estimates include:
-All membranes media, whether organic polymer or inorganic.
-All the components of an element or module necessary to hold the medium in place and to house it ready for use.
-All replacement media or modules supplied for installation in existing systems.
The estimates exclude:
-Any equipment outside the membrane module design.
-Any or all prefilter for membrane systems.
The present market is focusing in Europe (33.8%), and American Continent (39.9%) followed by Asia (23.5%) and rest of the world (Australia and Africa: 2.8%); this means that almost three-quarters of membranes sales were in Europe and the American continent[13]. Main membrane processes (presented in Fig. 1.1) are: 2 The market value includes the sale to original equipment manufacturers and replacement parts, from point of sale to end user.
MicroFiltration (MF), this sector-sale is driven by two operation procedures, dead-end or in-line filtration, in which the entire fluid flow is forced through the membrane under pressure, and cross-flow filtration where the feed solution is circulated across the surface of the filter, producing two streams: a clean particle-free permeate and a concentrated retentate containing the particles. Nowadays, most products-market is moving towards cross-flow style of filtration at the expense of dead-end filtration. It is used MF for the removal of pathogens (bacteria and some viruses) from potable water as a main line of tertiary treatment of wastewaters or the polishing of fresh water with membrane reactors. MF is presently extending its range downwards in particle size, in order to deal with this form of treatment in a single process step. Additionally, the MF application has considerably expanded[14], due to the development of new biopharmaceuticals and new research sectors like genomics.
In the case of Reverse Osmosis and NanoFiltration (RO/NF), these processes has grown rapidly both around 39% from 2006 to present[15]; NF is essential in water solutions, and applications for non-aqueous solutions, NF membranes are prepared to work under strong chemical conditions, so they are known as “essentially solvent resistant membranes”.
A good future is calling to NF process, as it will serve as an inexpensive pretreatment to current distillation techniques providing reduced overall costs and higher overall efficiency in the preparation of usable water. However, RO is still by far the largest of the two, and its market place is quite a mature one. There will be a continuing interest in RO processes for water desalination, especially in areas where water is already in short supply. This trend will be reinforced by rising of living standards. Chemical and pharmaceutical applications will continue to increase in number.
Abbildung in dieser Leseprobe nicht enthalten
Figure 1.1: Membrane and module sale for different process applications. RO Reverse Osmosis (includes NF NanoFiltration), UF UltraFiltration, MF MicroFiltration, ED Electro- Dyalisis, PV Pervaporation and GS GasSeparation.
Very closely following, UltraFiltration (UF) membrane market[16-17] represents about one-fifth of the total market. UF membranes and modules brought about US$ 600 million in sales for domestic treatment in 2011 with an expected growing rate of 10% a year. This rate of increase is significantly below (or higher) that all membrane processes presented in Fig. 1.1. In contrast to RO, the UF market [16-17] is shared by a large number of companies, but the leaders are Pall®, Amicon/Millipore® and Koch®. One of the largest industrial sectors for UF is still the recovery of electrocoating paints. UF membranes are also responsible for supplying pure water for the semiconductor industry. Growing demands of ultrahigh purity chemicals in this sector could also be supplied by UF with the availability of chemical-resistant membranes. Oil/water separation is now a large application for UF in industrial sectors such as metal cleaning and wool scouring, and is still growing with the implementation of new environmental legislation. The use of UF in the biotechnology industry is growing even faster than the sector itself.
The development of membrane reactors in Gas Separation (GS) is opening a number of new gas applications, from smaller applications ranging from dehydration of air and natural gas to organic vapor removal from air and Nitrogen streams. In this case, GS processes are growing rapidly from a small base, with a rate higher than 15% per year. This technology[18]is expanding rapidly and further growth is likely to continue for the next 10 years. Originally, the market for GS processes was close to US$ 1100 million, 6.2% in Fig. 1.1,but having much by far the highest growth rates of the membrane process segment.
Finally the “Other Liquid Separations Processes” category covers a range of membrane processes, operating by diffusion from the well-established, such as Dyalisis, Electro and Hemodialysis or ion exchange. In the case of Hemodialysis[19], is also a very important market, one million patients worldwide benefit from the process, each patient is dialysed approximately three times per week, with a dialyzer containing about 1m2 of membrane area. Economies of scale allow these devices to be produced for about US$15 million each, and discarded after one or two uses, that implies, around 50% of the total market.
Main applications use hollow fibres for waste recovery, food, pharmaceutical industries, analytical and medical applications, but also fuel cells, which are not yet fully commercialized. The total market volume excluding Hemodialysis in 2011 for the other liquid separations category is rising 6.8%.
Membrane field has advanced immensely[20], and it continues advancing, having a special recognition as alternative to conventional applications in the industrial world, which is due to the fact they cover a wide range of applications.
In conclusion, we need them, for environmental and economic sustainability and primary devices. Still some problems remain that need attention, like membrane fouling and membrane chemical stability. Even though, the advantages are more than the inconveniences: economy, environment, versatility and easy to use, membranes are a leading choice for industrial treatment applications and should continue so many years.
[...]
1 As molecular separation, fractionation, concentration, purification, clarification, emulsification, crystallization, etc.
- Citation du texte
- René Israel Peinador Dávila (Auteur), 2013, Characterization of Ultra and Nanofiltration Commercial Filters by Liquid-liquid Displacement Porosimetry, Munich, GRIN Verlag, https://www.grin.com/document/268782
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