Interaction of Scaling Species with Polymeric Materials
| dc.contributor.advisor | Li, Qilin | |
| dc.contributor.advisor | Getachew, Bezawit A | |
| dc.creator | Huang, Xiaochuan | |
| dc.date.accessioned | 2023-08-09T16:59:07Z | |
| dc.date.created | 2023-05 | |
| dc.date.issued | 2023-04-21 | |
| dc.date.submitted | May 2023 | |
| dc.date.updated | 2023-08-09T16:59:07Z | |
| dc.description | EMBARGO NOTE: This item is embargoed until 2029-05-01 | |
| dc.description.abstract | Polymeric membranes have been widely applied for water desalination due to their energy efficiency and relative low cost. However, the existence of scaling ions in the system and their interaction with the polymeric membranes, such as Ca2+ and SO42-, lead to the severe membrane scaling issue and the inefficient desalination performance. Membrane scaling and fouling have been the major constraint for the further improved desalination performance, which leads to the reduced water productivity and shortened membrane life. Additionally, the preferential transport of Ca2+ over monovalent ions in cation exchange membranes (CEM) results in the unstable and unsatisfactory water quality for direct portable use. Therefore, it is significant to thoroughly understand the impacts of different material properties on the interactions between scaling species and the polymeric membranes, and develop the desirable membrane materials that can meet the application needs. This study investigated the specific effects of material surface hydrophilicity and the structural property on the gypsum (CaSO4·2H2O) scaling control and particle attachment regulation, and developed a novel monovalent selective membranes that can be applied in electrodialysis (ED) for desalination and resource recovery. In the liquid environment, material surface hydrophobicity plays a very important role in gypsum scale formation. Due to the hydrophilic repulsion, increased hydrophilicity largely reduced the adhesion of gypsum particles that formed from bulk precipitation. Additionally, the material hydrophobicity strongly influenced the surface induced heterogeneous nucleation of gypsum. Without the interference of specific functional groups that can interact with Ca2+ or SO42- ions, surfaces of higher hydrophobicity promote gypsum surface nucleation, due to the reduced nucleation energy barrier. The ion adsorption on the surface also induced gypsum heterogeneous nucleation, however, the contribution was much smaller than that of hydrophobicity. Furthermore, gypsum scale formed from surface induced heterogeneous nucleation was highly irreversible, in contrast to those formed from homogeneous nucleation and bulk precipitation. These results suggest that surface induced heterogeneous nucleation is far more detrimental than homogeneous nucleation. The effects of dynamic surface coatings on particle fouling and gypsum scaling were investigated using synthesized stimuli-responsive polymer brushes. The attachment of polystyrene (PS) particles on thermos-responsive poly (N-isopropylacrylamide) (PNIPAM) was strongly influenced by the temperature, particle characteristics (i.e., size and functional groups) and the PNIPAM grafting density. PNIPAM of higher grafting density reduced the attachment of PS regardless of particle size. Less PS was attached on PNIPAM at low temperature (<33 ˚C) than that at high temperature (>33 ˚C), while the case was opposite for carboxylate PS, due to the different interactions between particles and exposed functional groups of PNIPAM. Notably, the fast dynamic structural change (every 1 min) of PNIPAM introduced by temperature switch was found to minimize the attachment of particles regardless of particle size and functional groups. Additionally, dynamic structural change also effective to remove particles that was attached within a short period of time with a removal rate of 70%. The dynamic structural change of pH-responsive poly (2-(dimethylamino)ethyl methacrylate) (PDMAEMA) was demonstrated promising for gypsum removal. PDMAEMA polymer brushes with a thickness of about 30 nm were coated on carbon nanotubes (CNT). Compared to pristine CNT, the PDMAEMA coated CNT significantly reduced the deposited gypsum due to the increased hydrophilicity. Moreover, with only 6 cycles of pH switch, over 86.4% of the gypsum was removed from the PDMAEMA coated CNT surface. As gypsum dissolution was negligible, this result indicated the important role of the dynamic structural change of PDEMA on gypsum removal. Additionally, the in-situ pH change was achieved from the water splitting with an alternating voltage (±2V) applied on the PDMAEMA-CNT. It was found 99% of the gypsum was removed with only 4 cycles of pH switch in synergy with bubble generation. A novel selective nanocomposite cation exchange membrane was synthesized to improve the monovalent/divalent permselectivity in the ED system. The membrane held a 3-layer structure including cation ion exchange polymer (CEP), Polysulfone and polyamide layer which provided the cation/anion separation, the mechanical strength and the divalent rejection function separately. The synthesized membrane demonstrated comparable electrical resistance to the commercial CEM due to the largely reduced membrane thickness. The monovalent/divalent permselectivity (e.g. Li+/Ca2+ permselectivity) achieved more than 6 even at a very low Li+/Ca2+ concentration ratio (1:10). Therefore, the synthesized membrane is promising for water desalination and resource recovery. More importantly, such membrane structure which allows the independent optimization of each functional layer provides versatile solutions to different application needs. | |
| dc.embargo.lift | 2029-05-01 | |
| dc.embargo.terms | 2029-05-01 | |
| dc.format.mimetype | application/pdf | |
| dc.identifier.citation | Huang, Xiaochuan. "Interaction of Scaling Species with Polymeric Materials." (2023) Diss., Rice University. <a href="https://hdl.handle.net/1911/115122">https://hdl.handle.net/1911/115122</a>. | |
| dc.identifier.uri | https://hdl.handle.net/1911/115122 | |
| dc.language.iso | eng | |
| dc.rights | Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder. | |
| dc.subject | Membrane desalination | |
| dc.subject | scaling and fouling | |
| dc.subject | surface hydrophilicity | |
| dc.subject | gypsum | |
| dc.subject | stimuli-responsive polymers | |
| dc.subject | monovalent selective membrane | |
| dc.title | Interaction of Scaling Species with Polymeric Materials | |
| dc.type | Thesis | |
| dc.type.material | Text | |
| thesis.degree.department | Civil and Environmental Engineering | |
| thesis.degree.discipline | Engineering | |
| thesis.degree.grantor | Rice University | |
| thesis.degree.level | Doctoral | |
| thesis.degree.name | Doctor of Philosophy |