Abstract

Forward osmosis (FO) has attracted significant interest as a promising alternative to reverse osmosis (RO) in membrane-based water desalination applications. FO water flux, salt rejection and reverse solute flux are three critical parameters affecting membrane performance. Thin film composite (TFC) membranes have been widely used in FO processes. A typical TFC membrane consists of a rejection polyamide (PA) layer on top of a highly porous support layer. In the current study, carboxyl functionalized multi-walled carbon nanotubes (F-MWCNTs) were used as nano-fillers in the membrane rejection layer to enhance the FO membrane performance. Polyamide (PA) thin film nano-composite (TFNC) membranes were synthesized on top of polysulfone (PSF) porous support layers by interfacial polymerization (IP) using m-phenylenediamine (MPD) in water and trimesoyl chloride (TMC) in hexane. The PSF support layer was synthesized by phase inversion in a water bath of a casting solution of PSF and polvinylpyrrolidone (PVP) (pore forming agent) dissolved in anhydrous dimethyl formamide (DMF). Multi-walled carbon nanotubes were functionalized by oxidation in strong acidic solutions, and then incorporated in the MPD aqueous solution during IP. For the support layer, PSF and PVP concentrations were varied while monomers (MPD, TMC) concentrations, contact time and curing temperature were varied for the rejection layer. Experimental designs for both the support and the rejection layers were carried out using Design-Expert software including statistical analysis to identify the most significant factors affecting the membrane performance. The support layer of 18 wt% PSF and 2 wt% PVP was selected as the membrane support with the highest possible FO water flux and minimum reverse solute flux while the PA rejection layer of 4 wt/vol% MPD and 0.2 wt/vol% TMC was selected as the membrane rejection layer with a salt rejection of 88.30±0.11%. Finally, the amount of F-MWCNTs was varied from 0.01 to 0.2 wt/vol% to study their effect on the membrane morphology and performance. The synthesized membranes were characterized using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectrophotometry (FTIR) and Brunauer-Emmett-Teller gas adsoprtion analysis (BET). FO performance was investigated using deionized water as the feed solution and 2 M NaCl as the draw solution. It was found that F-MWCNTs enhanced the membrane hydrophilicity and surface roughness that led to increased FO water flux. Most importantly, the salt rejection was also increased at low concentrations of F-MWCNTs (< 0.05 wt/vol%). The membrane with 0.01 wt/vol% F-MWCNTs showed the highest salt rejection (90.05±0.25%) with a FO water flux of 50.23±0.93 L/m2 h and a reverse solute flux of 2.76±0.21 g/m2h, thus outperforming thin film composite FO membranes reported in literature.

Department

Chemistry Department

Degree Name

MS in Chemistry

Date of Award

6-1-2018

Online Submission Date

May 2018

First Advisor

Ramadan, Adham, Esawi, Amal

Committee Member 1

El Sayed, Mayyada

Committee Member 2

Gadallah, Hanaa Gamal

Document Type

Thesis

Extent

178 p.

Rights

The author retains all rights with regard to copyright. The author certifies that written permission from the owner(s) of third-party copyrighted matter included in the thesis, dissertation, paper, or record of study has been obtained. The author further certifies that IRB approval has been obtained for this thesis, or that IRB approval is not necessary for this thesis. Insofar as this thesis, dissertation, paper, or record of study is an educational record as defined in the Family Educational Rights and Privacy Act (FERPA) (20 USC 1232g), the author has granted consent to disclosure of it to anyone who requests a copy.

IRB

Not necessary for this item

Comments

First and foremost, I would like to express my sincere gratitude to my advisors, Prof. Adham Ramadan and Prof. Amal Esawi for their continuous support throughout my master studies. They taught me a lot inside and outside the lab, and I really had great opportunities and experiences by working under their supervision. I am so grateful to Prof. Adham Ramadan, who supported and encouraged me from the first day I joined AUC as a staff member. He taught me how to organize my lab work and how to write my thesis efficiently. I always consider you as my role model. Thank you Prof. Adham for guiding and encouraging me. I would like to thank Prof. Amal Esawi, who taught and guided me during my studies. I never forget her simple explanation and clear analysis to solve any research challenges. She has responded to me whenever I need her help, and she called for regular meetings to discuss my work progress. Thank you Prof. Amal for your encouragement, effort and kindness. I would like to thank The American University in Cairo for funding my studies as a staff member. I am really happy to work and study in this great university. AUC is a well-developed research place that give all the possible opportunities to achieve promising research projects. I would like to thank all my professors in Chemistry Department for their continuous help during my studies, and I would to express my intense appreciation to Prof. Pakinam Askalani for the course of structural determination methods that helped me. I would like to thank Dr. Nahed Yacoub for helping and supporting me. Thank you Dr. Nahed for everything. I would like to thank Dr. Mohamed El-Morsi in Mechanical Engineering Department for his help with setting up the test cell. I really appreciate his great efforts. I also wish to thank Dr. Hatem Elayat for the design of experiments course that helped in the statistical analysis. I would like to thank all my colleagues and friends for their support and encouragement during my Master program. I am so grateful to Ayat Ashour, Ahmed Nour, Hoda Saad, Madina Ashour, Nouran Ashraf, Osama Elsayed, Samir Nabhan and Sherine Saad for their extensive inspiration. The pursuit of my thesis project could not be done without the support of my family. I would like to thank my parents for loving and pushing me to finalize the Master program. I would like to thank my lovely brother and sister, Abdel Fattah Omaia and Eman Omaia for inspiring me.

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