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    Carbon Dioxide Nucleation as a Novel Cleaning Method for Sodium Alginate Fouling Removal from Reverse Osmosis Membranes desalination

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    Name:
    PhD_Dissertation_Heba_Alnajjar_Summer_2017.pdf
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    6.901Mb
    Format:
    PDF
    Description:
    Heba Alnajjar Dissertation
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    Type
    Dissertation
    Authors
    Alnajjar, Heba cc
    Advisors
    Wang, Peng cc
    Ghaffour, NorEddine cc
    Committee members
    Amy, Gary L.
    Leiknes, TorOve cc
    Lai, Zhiping cc
    Program
    Environmental Science and Engineering
    KAUST Department
    Biological and Environmental Science and Engineering (BESE) Division
    Date
    2017-05
    Embargo End Date
    2018-06-19
    Permanent link to this record
    http://hdl.handle.net/10754/625069
    
    Metadata
    Show full item record
    Access Restrictions
    At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2018-06-19.
    Abstract
    The use of Reverse osmosis (RO) membranes have been significantly increasing in water desalination, and the main operational obstacle in RO desalination plants is membrane fouling. Among other solutes, dissolved biopolymers, such as polysaccharides can lead to severe membrane fouling especially with the addition of calcium ions because of the complexation formation between the surface of membrane and foulants materials. However, this complexation can also take place in the feed bulk, resulting in foulants aggregates formation. Although there are some physical techniques that can maintain the membrane performance without reducing its lifetime, only chemical cleanings are still commonly used in RO plants. In this study, a novel cleaning method is proposed to restore the membrane performance by removing the deposited foulants without reducing the membrane lifetime. The cleaning method is based on using water saturated with dissolved CO2 gas, and its principle is based on producing spontaneous CO2 bubbles due to local pressure difference leading to nucleation of bubbles throughout the membrane surface, especially at nucleation sites, which improve the cleaning efficiency. Alginic acid sodium salt was used as a model of polysaccharides foulants in presence of different concentrations of NaCl and calcium ions aiming to enhance membrane fouling, and then CO2 cleaning solution efficiency, in terms flux recovery (FR), was tested under different operating conditions and compared to other cleaning methods. Average FR of 20%±3, 25%±3 and 80%±3 for MilliQ water, a cleaning solution at pH4, and CO2 solution at 6 bar, 0.17 m/s, and 23 ̊C ±0.2 for 6 minutes were obtained, respectively. The efficiency of this novel cleaning method was also compared to direct osmosis overnight, and the average flux was comparable (about 60%±3), though that the cleaning time was significantly different. Various calcium concentrations (0-10 mM) were added in the alginate solution to study the fouling behavior in terms of the potential for bulk complexation to form cake alginate layer on the membrane surface rather than a gel layer, and the role of CO2 bubbles nucleation to remove foulants was investigated. This cleaning method can be considered as an alternative more environmentally friendly technique in RO application.
    Citation
    Alnajjar, H. (2017). Carbon Dioxide Nucleation as a Novel Cleaning Method for Sodium Alginate Fouling Removal from Reverse Osmosis Membranes desalination. KAUST Research Repository. https://doi.org/10.25781/KAUST-JU308
    DOI
    10.25781/KAUST-JU308
    ae974a485f413a2113503eed53cd6c53
    10.25781/KAUST-JU308
    Scopus Count
    Collections
    Biological and Environmental Science and Engineering (BESE) Division; Environmental Science and Engineering Program; PhD Dissertations

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