We investigated the relationship between silica scaling and protein fouling in reverse osmosis (RO). Flux decline caused by combined scaling and fouling was compared with those by individual scaling or fouling. Bovine serum albumin (BSA) and lysozyme (LYZ), two proteins with opposite charges at typical feedwater pH, were used as model protein foulants. Our results demonstrate that water flux decline was synergistically enhanced when silica and protein were both present in the feedwater. For example, flux decline after 500 min was far greater in combined silica scaling and BSA fouling experiments (55 ± 6% decline) than those caused by silica (11 ± 2% decline) or BSA (9 ± 1% decline) alone. Similar behavior was observed with silica and LYZ, suggesting that this synergistic effect was independent of protein charge. Membrane characterization by scanning electron microscopy and Fourier transform infrared spectroscopy revealed distinct foulant layers formed by BSA and LYZ in the presence of silica. A combination of dynamic light scattering, transmission electron microscopy , and energy dispersive X-ray spectroscopy analyses further suggested that BSA and LYZ facilitated the formation of aggregates with varied chemical compositions. As a result, BSA and LYZ were likely to play different roles in enhancing flux decline in combined scaling and fouling. Our study suggests that the coexistence of organic foulants, such as proteins, largely alters scaling behavior of silica, and that accurate prediction of RO performance requires careful consideration of foulant-scalant interactions.

No abstract

No abstract

Black polyimide (BPI) is increasingly in demand for the development of photoelectric devices in place of yellow transparent polyimide, but BPI doped with carbon black shows serious insulation and mechanical performance deficiencies due to pinholes and uneven dispersion. Intrinsically BPI has thus attracted increasing interest in science and industry. Anthraquinone derivatives have an ample high molar extinction coefficient (ε), and appending as many auxochromes (−OH and −NH2) as possible on the anthraquinone skeleton can extend its light absorption range, thereby achieving complete UV–visible light absorption. However, the greatest obstacle to its application in BPI is retaining the monomer bifunctionality to avoid gel formation. In this work, a linearly polymerizable anthraquinone derivative, 2,4,5,7-tetraamino-1,8-dihydroxyanthracene-9,10-dione (4NADA), has been developed. Structural analysis of this monomer bearing multiple active groups by 1H NMR, Fourier-transform infrared, and theoretical calculations has demonstrated that the auxochrome groups show different nucleophilic activities owing to the formation of intramolecular hydrogen bonds, such that only p-amino groups (2- and 7-positions) can participate in the polymerization reaction. Subsequently, 4NADA was copolymerized into a Kapton-type polyimide. We found that low-level introduction of 4NADA (4%) afforded a spectrally BPI film that maintained the electrical insulation and heat resistance properties of polyimide. This method, equivalent to embedding a black monomer in polyimide chains, has merits of economy, universality, process consistency, ready accessibility, and superior performance.

No abstract