Environmental Engineering Reference
In-Depth Information
efficient AOPs developed to decolorize and/or degrade organic pollutants for environment protection. The fundamentals involved
in the main applications of typical methods such as fenton, electro-fenton, photo-fenton, ozonation, and UV methods are delib-
erated and discussed in great detail. Various combinations of these processes and their industrial applications are outlined in
this study.
13.3 visiOn Of nAnOfiltrAtiOn And tHe Wide dOmAin Of memBrAne science And its
imPAct On scientific reseArcH Pursuit
It is urgent and imperative to review and discuss the past to provide a compelling vision for the future. The research domain of
membrane science and nanofiltration is undergoing rapid and spontaneous changes. The scientist's vision has widened and the
emerging scientific imagination is compelling. The purpose of this chapter is to review the history of development of mem-
branes and membrane processes particularly nanofiltration for water production in general and seawater desalination in
particular. We want to highlight some new trends in the following areas: membrane development, membrane characterization,
membrane transport, and membrane system design. The future prospects in the four areas are discussed in minute detail.
membrane development deals with recent progress in the development of reverse osmosis (RO) membranes used for desalina-
tion. There are two different approaches, both based on in situ polycondensation. One is to develop membranes for desalination
of brackish water operable at ultralow pressure and the other is to develop membranes operable at high pressures to achieve high
pure water recovery in seawater desalination. In the membrane characterization section, atomic force microscopy (Afm) is
featured as a new tool to investigate the nature of membrane surfaces. The effects of surface roughness, which can be measured
by Afm, on membrane productivity and membrane fouling are outlined.
An in-depth insight into the drawbacks of nanofiltration is presented by Van der Bruggen et al. [1]. According to their definition,
nanofiltration was defined as “a process intermediate between reverse osmosis and ultrafiltration that rejects molecules which have a
size in the order of one nanometer.” They have reviewed every aspect of the subject of nanofiltration. nanofiltration was introduced in
the late 1980s, mainly aiming at combined softening and organics removal. Since then, the applications of nanofiltration have extended
tremendously. An insight into the branch of nanofiltration showed the giant steps science has taken for the well-being of mankind.
The review delineates six challenging areas for nanofiltration where solutions and remedies are still scarce: (i) avoiding mem-
brane fouling, and the possibility of remediation; (ii) improving the separation between solutes that can be achieved; (iii) further
treatment of concentrates and an increase in the efficiency of separation; (iv) chemical resistance and limited/short life span of
membranes; (v) insufficient and low rejection of pollutants in water treatment; and (iv) the urgent need for modeling and simula-
tion tools. This chapter gives a holistic idea of the state of the art in this field and what the scientific fraternity should aim at as
well as its vision. All six thrust areas or domains are interlinked and could possibly reach out in a greater way to bring about rem-
edies and solutions.
nanofiltration has new possibilities such as in drinking water production, arsenic removal, the removal of pesticides, the
production of endocrine disruptors and chemicals, and partial desalination.
matsuura [2] dealt with progress in membrane science and technology for seawater desalination in a phenomenal and visionary
review paper. This review outlines some new trends in the following four areas: membrane development, membrane character-
ization, membrane transport, and membrane system design. future targets, vision, and prospects in these four areas are delin-
eated. The review deals with membrane development highlighting recent progress in the development of RO membranes used for
desalination. There are two different approaches, both based on in situ polycondensation. One is to develop and devise mem-
branes used for desalination of brackish water operable at ultralow pressures, and the other is to develop and devise membranes
operable at high pressures to achieve high pure water recovery in seawater desalination. In the membrane characterization section,
the application of Afm in investigating and discovering the science behind membrane surfaces is discussed. Also, the review
paper by matsuura (2001) deals with transport models made primarily for charged membranes. membrane transport deals with
transport models made primarily for charged membranes. Hybrid systems for seawater desalination in which membrane processes
are incorporated are discussed. According to the Conclusion section in this review paper, there is an enormous and sizable poten-
tial to reduce desalination costs by combining membrane processes with novel separation techniques/unit operations.
Sidek et al. [3] reviewed a phenomenal paper on the factors governing the nanofiltration membrane separation process. The
main objectives of this paper are to review the performance of nanofiltration membranes in removing unwanted particles from
a solution by evaluating the factors, such as Donnan and steric interaction and transmembrane pressure (TmP), that influence
rejection by the membrane. The right combination of membrane pore size (steric effect) and its effective charge density (Donnan
effect) leads to optimum separation performance. However, the effect of TmP on nanofiltration rejection is not consistent. At
high TmP, rejection can be either increased or decreased, depending on other operating parameters such as pH, ionic strength,
the presence of salt. pH and feed concentration (ionic strength) play a significant role in nanofiltration membrane separation.
