Reverse Osmosis membranes have been successfully proven to remove almost 99% of chemicals
dissolved in seawater. However, removal of certain trace elements, such as boron is challenging
and relatively low for seawater reverse osmosis desalination plants compared to thermal
desalination plants. Boron is naturally occurring and is present in seawater at an average
concentration of 4.5-5 mg/L. While boron is a vital element, its toxicity has been proven on crops,
animals and possibly humans. Additionally, boron should be removed to comply with the current
guideline value of 0.5 mg/L, for drinking water, issued by the World Health Organization (WHO),
which is barely attained by a single-pass process seawater reverse osmosis plant. Currently, multipass
reverse osmosis membrane operations with pH modifications are the only valid method for
boron removal. However, this is not economically efficient as it requires higher energy and
chemicals consumptions. The objective of this study was to investigate boron removal by
commercial TFC RO membranes in addition to custom-made KAUST-synthesized TFC
membrane.
Five membrane samples were examined: Toray, Sepro, Koch, and KAUST in-house
synthesized membrane. Three different feed pH conditions were used: pH6, pH8, and pH10.
Filtration experiments were conducted in two parts. In experiment 1, all five membranes were
examined for boron rejection in a dead-end permeation system, whereas in experiment 2 the two
membranes with the highest boron rejection from experiment 1 were tested in a cross-flow system.
Permeate and feed samples were taken continuously and analyzed for boron concentration,
rejection calculation. Membrane surfaces were characterized according to hydrophilicity,
roughness and surface charge. The results showed for all the tested membranes that boron rejection
increased as the feed pH increased. KAUST, defect-free TFC, showed the highest performance for
boron rejection for all pH conditions, although, it shows the roughest surface. Toray membranes
80LB and 80B exhibited the second highest boron rejection and had the most negatively charged
membrane surfaces.
It was observed in this study that the rejection of boron by a membrane is due
to size exclusion and charge repulsion mechanisms. It was concluded that, the KAUST, defect free
TFC has the potential to be applicable for boron rejection in industrial application as it has better
boron rejection than commercially available RO membranes.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/627887 |
| Date | 04 1900 |
| Creators | Al Sunbul, Yasmeen |
| Contributors | Pinnau, Ingo, Physical Sciences and Engineering (PSE) Division, Peinemann, Klaus-Viktor, Han, Yu |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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