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Publication WS2 deposition on cross-linked polyacrylonitrile with synergistic transformation to yield organic solvent nanofiltration membranes(Elsevier, 2019-06-27) Hui Min Tham; Susilo Japip; Tai-Shung Chung; CHEMICAL & BIOMOLECULAR ENGINEERINGUsing liquid phase exfoliation (LPE) methods established in literature, several different tungsten (IV) disulfide (WS2) dispersions were prepared in solvents ranging from NMP, ethanol/water to pure water via sonication under ambient conditions. These various dispersions were then deposited directly onto cross-linked ultrafiltration-level polyacrylonitrile (PAN) flat sheet membranes through a pressure-assisted filtration process to produce ready-to-use membranes without any additional modifications. To evaluate and compare the performances of the various membranes produced, organic solvent nanofiltration (OSN) was utilized as the testing method while also representing a potential application of these fabricated membranes. After observing and comparing the outcomes of depositing different WS2 dispersions, deposition of the NMP dispersion was found to yield a promising membrane due to a concurrent synergistic densification effect with positive impacts on membrane performance. Thus, further emphases were placed on studying the use of different initial WS2 concentrations and longer sonication times in NMP dispersions. After the optimization, the composite membrane consisting of WS2 on cross-linked PAN substrates shows impressive performance with a high pure ethanol permeance of 43.35 L m−2 h−1 bar−1, a rejection of 86% towards Remazol Brilliant Blue R (Mw = 626.54 g/mol) and a long-term sustained rejection of 99% towards Evans Blue (Mw = 960.81 g/mol) in ethanol.Publication Allelopathic effects of macroalgae on Pocillopora acuta coral larvae(2019) JENNY FONG; ZI WEI LIM; BAUMAN, ANDREW GEOFFREY; VALIYAVEETTIL, SURESH; LAWRENCE M. LIAO; YIP ZHI TING; PETER ALAN TODD; CHEMISTRY; BIOLOGICAL SCIENCESAllelopathy has been proposed as a key mechanism mediating coral–algal interactions; however, few studies have tested macroalgal allelochemicals on coral larvae. In this study, we examined the effects of crude extracts from four macroalgal species on Pocillopora acuta larvae under different exposure conditions. Larval mortality increased considerably with increasing concentrations of Bryopsis sp., Endosiphonia horrida, and Lobophora sp. extracts. Increasing E. horrida and Lobophora sp. extract concentrations also substantially decreased larval settlement. No detectable effects on larvae were observed in Hypnea pannosa extracts. Further, while larval mortality increased with exposure duration to Lobophora sp. extracts, larval settlement was enhanced at 12 h exposure, but reduced at shorter and longer durations. Our results emphasize that macroalgal chemical effects are highly dependent on macroalgal species and exposure conditions. On reefs dominated by allelopathic macroalgae, the survivorship and settlement of coral larvae are potentially constrained, thereby limiting the recovery of degraded reefs.Publication From ultrafiltration to nanofiltration: Hydrazine cross-linked polyacrylonitrile hollow fiber membranes for organic solvent nanofiltration(Elsevier, 2017-08-12) Hui Min Tham; Kai Yu Wang; Dan Hua; Susilo Japip; Tai-Shung Chung; CHEMICAL & BIOMOLECULAR ENGINEERINGUltrafiltration-level polyacrylonitrile (PAN) hollow fiber membranes were molecularly engineered via chemical cross-linking to obtain membranes suitable for use in organic solvent nanofiltration (OSN). By adjusting the dope composition and spinning conditions, hollow fibers possessing a desirable sponge-like cross-section with minimal macrovoids were obtained. Hydrazine monohydrate was used as the cross-linker and the effects of cross-linking time on the membrane's separation performance were investigated. X-ray photoelectron spectroscopy was used to elucidate the possible reactions and indicated the successful cross-linking of the PAN hollow fiber membranes. The cross-linked nanofiltration-level hollow fibers were subjected to OSN tests using ethanol and dyes as model feed solutions. With this simple and effective modification, the PAN hollow fiber membranes were able to achieve a pure ethanol permeance of 2.32 L m−2 h−1 bar−1 and an impressive Remazol Brilliant Blue R (Mw 626.54 g mol−1) rejection of more than 99.9%. Given the ease of fabrication and modification, these PAN hollow fibers represent a significant step forward in the use of hollow fiber membranes for OSN, particularly in larger-scale operations.Publication Early evidence of microplastics on seagrass and macroalgae(2020-01-28) NICHOLAS SENG; LAI WEN YA SAMANTHA; JENNY FONG; MUHAMMAD FAIQ SALEH; CLEMENT CHENG; CHEOK ZI YU; PETER ALAN TODD; BIOLOGICAL SCIENCESMicroplastic accumulation on marine macrophytes, such as macroalgae and seagrasses, is a potentially critical but overlooked pathway by which microplastics enter the marine food web. Despite the possible significance of this pathway, few studies have examined the presence of microplastics on macrophytes found in situ. We quantified the density of microplastics found on the surfaces of three species of intertidal seagrasses (Cymodocea rotundata, Cymodocea serrulata and Thalassia hemprichii) and two species of subtidal macroalgae (Padina sp. and Sargassum ilicifolium), and found significantly higher microplastic densities on seagrasses than on macroalgae. However, we found no relationships between microplastic density and epibiont cover in either seagrass or macroalgae. Our study has provided early evidence of microplastics on macrophyte surfaces in situ, being the first such evidence for macroalgae, and the second for seagrasses.