Effect of coexisting metal ions on the degradation of polyamide reverse osmosis membrane by hypochlorite treatment

Abstract

A Dissertation submitted to the Graduate School of Engineering HIROSHIMA UNIVERSITY By CERVINIA VELASCO MANALO In partial fulfillment of the requirements for the degree of Doctor of Engineering March 2016 Evaluation of Biofouling and Its Control by Hypochlorite on Polyamide Reverse Osmosis Membranes ( RO ) Cervinia V. Manalo The following people and organizations had been invaluable towards the completion of this doctorate degree and during the course of this academic journey, and for that I would like to express my sincerest and heartfelt gratitude: My professors and mentors from the Green Process Engineering Laboratory: Dr. Wataru Nishijima for his guidance and immense knowledge during the time of my research and for his valuable insights and efforts during the preparation of my papers; Dr. Satoshi Nakai, my adviser, for all the constructive opinions and advices, for his significant support during my applications for scholarship grants, and for his constant push in making me accomplish and finish this degree on time; Dr. Tetsuji Okuda for all his help during my application as a researcher and as a graduate student, for his continued guidance during my experiments and research, for ensuring my financial support as a part-time research assistant (RA) during my stay here in Japan, and for his care and kindness; My review committee, Dr. Toshinori Tsuru, Dr. Tomohisa Yoshioka, and Dr. Wataru Nishijima for their challenging questions and insightful comments that helped me write a better dissertation, for the constant encouragements, and for rendering their time and support despite the time constraints during my preliminary and final defense; CREST (Core Research for Evolutionary Science and Technology) under the project "Development of ROBUST reverse osmosis (RO)/nanofiltration (NF) membranes for various types of water sources and the Department of Chemical Engineering for the financial support given to me as a part-time RA, which enabled me to pursue my studies while living in Saijo;The scholarship grants awarded by Higashi-Hiroshima International Soroptomist

Controlling biofouling and disinfection by-product formation during reverse osmosis treatment for seawater desalination

“…Moreover, the rejection both of conductivity (a surrogate indicator of salts) and boron dramatically decreased from 99.4% to 24.0% and 76.3% to 0.0%, respectively. These deterioration effects caused by chlorine are consistent with those measured in previous studies [18,19], indicating that chlorine degrades the cross-linked polyamide separation layer through hydrolysis and deteriorates the separation performance of the membrane. In contrast to chlorine, stabilized hypobromite exposure caused only a slight reduction in pure water permeability from 3.0 to 1.8 L/m 2 hbar.…”

Deterioration Mechanism of a Tertiary Polyamide Reverse Osmosis Membrane by Hypochlorite

“…Virgin and treated membranes were washed with Milli-Q water and then set in a cross-flow cell (Figure S1, Tritec Co., Ltd., Tokyo, Japan), in which the effective membrane surface area was 37.4 cm 2 . Model salt water 25 (1 L) containing 0.015 M NaCl, 0.01 M NaH 2 PO 4 • 2H 2 O, and 0.01 M NaOH (pH 8) was fed through the cell at a flow rate of 50 mL/min (a crossflow rate of 1.3 cm/min) at 25 °C under 1.5 MPa. During the first 4 min of filtration, the permeate and concentrate were discarded; after this time, both were cycled back to the feed tank.…”

Membrane fouling, chemical cleaning and separation performance assessment of a chlorine-resistant nanofiltration membrane for water recycling applications

“…The DK NF membrane revealed a similar but less deterioration in conductivity rejection from 61.8 to 21.9 % from 0 to 5×10 4 ppm-h. The considerable increase in the permeability of the commercial membranes after chlorine exposure is the indication of the degraded membrane by chlorine attack [23].…”

“…Exposing PA-based NF membranes to chlorine can lead to the degradation of amide bonds (-CO-NH-) of the PA structure [21]. Extended contact with chlorine ultimately causes the deterioration in separation performance [22][23][24]. To avoid the degradation issue, significant research work has devoted to the development of chlorine-resistant PA membranes [25][26][27][28][29].…”