ABSTRACT
In a single-step spinning process, we create a thin-walled, robust hollow fiber support made of Torlon® polyamide-imide featuring an intermediate polyethyleneimine (PEI) lumen layer to facilitate the integration and covalent attachment of a dense selective layer. Subsequently, interfacial polymerization of m-phenylenediamine and trimesoyl chloride forms a dense selective polyamide (PA) layer on the inside of the hollow fiber. The resulting thin-film composite hollow fiber membranes show high NaCl rejections of around 96% with a pure water permeability of 1.2 LMH/bar. The high success rate of fabricating the thin-film composite hollow fiber membrane proves our hypothesis of a supporting effect of the intermediate PEI layer on separation layer formation. This work marks a step towards the development of a robust method for the large-scale manufacturing of thin-film composite hollow fiber membranes for reverse osmosis and nanofiltration.
ABSTRACT
Polymersomes made of amphiphilic diblock copolymers are generally regarded as having higher physical and chemical stability than liposomes composed of phospholipids. This enhanced stability arises from the higher molecular weight of polymer constituents. Despite their increased stability, polymer bilayers are solubilized by detergents in a similar manner to lipid bilayers. In this work, we evaluated the stability of poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL)-based polymersomes exposed to three different detergents: N-octyl-ß-d-glucopyranoside (OG), lauryldimethylamine N-oxide (LDAO), and Triton X-100 (TX-100). Changes in morphology, particle size distribution, and concentrations of the polymersomes were evaluated during the titration of the detergents into the polymersome solutions. Furthermore, we discussed the effect of detergent features on the solubilization of the polymeric bilayer and compared it to the results reported in the literature for liposomes and polymersomes. This information can be used for tuning the properties of PEG-PCL polymersomes for use in applications such as drug delivery or protein reconstitution studies.
ABSTRACT
Although forward osmosis (FO) membranes have shown great promise for many applications, there are few studies attempting to create a systematization of the testing conditions at a pilot scale for FO membrane modules. To address this issue, hollow fiber forward osmosis (HFFO) membrane modules with different performances (water flux and solute rejection) have been investigated at different operating conditions. Various draw and feed flow rates, draw solute types and concentrations, transmembrane pressures, temperatures, and operation modes have been studied using two model feed solutions-deionized water and artificial seawater. The significance of the operational conditions in the FO process was attributed to a dominant role of concentration polarization (CP) effects, where the selected draw solute and draw concentration had the biggest impact on membrane performance due to internal CP. Additionally, the rejection of the HFFO membranes using three model solutes (caffeine, niacin, and urea) were determined under both FO and reverse osmosis (RO) conditions with the same process recovery. FO rejections had an increase of 2% for caffeine, 19% for niacin, and 740% for urea compared to the RO rejections. Overall, this is the first extensive study of commercially available inside-out HFFO membrane modules.
ABSTRACT
The increasing use of engineered nanoparticles in customer products results in their accumulation in water sources. In this experimental study, we investigated the role of surfactant type (cationic, anionic and non-ionic) and concentration on fouling development, nanoparticle rejection and fouling irreversibility during dead-end ultrafiltration of model silica nanoparticles. Our work demonstrates that the type of surfactant influences the nanoparticle stability, which in turn is responsible for differences in fouling behavior of the nanoparticles. Moreover, the surfactant itself interacts with the PES-PVP membrane and contributes to the fouling as well. We have shown that anionic SDS (sodium dodecylsulfate) does not interact extensively with the negatively charged silica nanoparticles and does not change significantly the surface charge and size of these nanoparticles. Adsorption of the cationic CTAB (cetyltrimethylammonium bromide) onto the silica nanoparticles causes charge transition and nanoparticle aggregation, whereas non-ionic TX-100 (Triton X-100) neutralizes the surface charge of the nanoparticles but does not change significantly the nanoparticle size. The most severe fouling development was observed for the silica nanoparticle - TX-100 system, where nanoparticles in the filtration cake formed exhibited the lowest repulsive interactions. Rejection of the nanoparticles was also highest for the mixture containing silica nanoparticles and TX-100.
