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

Handle URI:
http://hdl.handle.net/10754/625069
Title:
Carbon Dioxide Nucleation as a Novel Cleaning Method for Sodium Alginate Fouling Removal from Reverse Osmosis Membranes desalination
Authors:
Alnajjar, Heba ( 0000-0003-1676-506X )
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.
Advisors:
Wang, Peng ( 0000-0003-0856-0865 ) ; Ghaffour, Noreddine ( 0000-0003-2095-4736 )
Committee Member:
Amy, Gary L.; Leiknes, TorOve ( 0000-0003-4046-5622 ) ; Lai, Zhiping ( 0000-0001-9555-6009 )
KAUST Department:
Biological and Environmental Sciences and Engineering (BESE) Division
Program:
Environmental Science and Engineering
Issue Date:
May-2017
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorWang, Pengen
dc.contributor.advisorGhaffour, Noreddineen
dc.contributor.authorAlnajjar, Hebaen
dc.date.accessioned2017-06-19T11:00:22Z-
dc.date.available2017-06-19T11:00:22Z-
dc.date.issued2017-05-
dc.identifier.urihttp://hdl.handle.net/10754/625069-
dc.description.abstractThe 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.en
dc.language.isoenen
dc.subjectCarbon Dioxide Nucleationen
dc.subjectSodium Alginate Foulingen
dc.subjectReverse Osmosis Membranesen
dc.subjectMembranes Desalinationen
dc.subjectMembrane Cleaningen
dc.subjectPhysical Cleaningen
dc.titleCarbon Dioxide Nucleation as a Novel Cleaning Method for Sodium Alginate Fouling Removal from Reverse Osmosis Membranes desalinationen
dc.typeDissertationen
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberAmy, Gary L.en
dc.contributor.committeememberLeiknes, TorOveen
dc.contributor.committeememberLai, Zhipingen
thesis.degree.disciplineEnvironmental Science and Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id112321en
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