Adsorption of organic foulants on nanofiltration (NF) and reverse osmosis (RO) membrane surfaces strongly affects subsequent fouling behavior by modifying the membrane surface. In this study, impact on organic foulant adsorption of specific chemistries including those in commercial thin-film composite membranes was investigated using self-assembled monolayers with seven different ending chemical functionalities (-CH(3), -O-phenyl, -NH(2), ethylene-glycol, -COOH, -CONH(2), and -OH). Adsorption and cleaning of protein (bovine serum albumin) and polysaccharide (sodium alginate) model foulants in two solution conditions were measured using quartz crystal microbalance with dissipation monitoring, and were found to strongly depend on surface functionality. Alginate adsorption correlated with surface hydrophobicity as measured by water contact angle in air; however, adsorption of BSA on hydrophilic -COOH, -NH(2), and -CONH(2) surfaces was high and dominated by hydrogen bond formation and electrostatic attraction. Adsorption of both BSA and alginate was the fastest on -COOH, and adsorption on -NH(2) and -CONH(2) was difficult to remove by surfactant cleaning. BSA adsorption kinetics was shown to be markedly faster than that of alginate, suggesting its importance in the formation of the conditioning layer. Surface modification to render -OH or ethylene-glycol functionalities are expected to reduce membrane fouling.
Basin-scale calcification rates are highly important in assessments of the global oceanic carbon cycle. Traditionally, such estimates were based on rates of sedimentation measured with sediment traps or in deep sea cores. Here we estimated CaCO 3 precipitation rates in the surface water of the Red Sea from total alkalinity depletion along their axial flow using the water flux in the straits of Bab el Mandeb. The relative contribution of coral reefs and open sea plankton were calculated by fitting a Rayleigh distillation model to the increase in the strontium to calcium ratio. We estimate the net amount of CaCO 3 precipitated in the Red Sea to be 7.3 ± 0.4·10 10 kg·y −1 of which 80 ± 5% is by pelagic calcareous plankton and 20 ± 5% is by the flourishing coastal coral reefs. This estimate for pelagic calcification rate is up to 40% higher than published sedimentary CaCO 3 accumulation rates for the region. The calcification rate of the Gulf of Aden was estimated by the Rayleigh model to be ∼1/2 of the Red Sea, and in the northwestern Indian Ocean, it was smaller than our detection limit. The results of this study suggest that variations of major ions on a basin scale may potentially help in assessing long-term effects of ocean acidification on carbonate deposition by marine organisms.T he anthropogenic CO 2 accumulating rapidly in the atmosphere acidifies the ocean surface waters at an increasing rate (1). Ocean acidification lowers the saturation state of CaCO 3 minerals, making it harder for calcifying organisms to build their skeletons (2). The actual effect of ocean acidification on biogenic CaCO 3 precipitation rates is highly variable and species specific (3). Since this issue is of considerable importance to the functioning of many marine ecosystems, it has been intensively studied during recent years (4, 5). Most field studies are, however, site specific, conducted separately on marginal and pelagic environments. Here we provide a basin-scale (the whole Red Sea) approach to assess simultaneously the overall calcification rates of coral reefs and pelagic plankton communities using nonconservative geochemical trends.The Red Sea (RS) is a long (∼2,250 km) and narrow (maximum width ∼350 km) embryonic ocean basin extending from 12.5°N to 30°N (Fig. 1). It is connected to the Gulf of Aden (GoAd) and the Indian Ocean (IO) by the shallow and narrow straits of Bab el Mandeb (BeM) (6). The excess evaporation (over precipitation) is ∼2 m·y −1 (7), and the absence of any significant river entering the RS drives a northward thermohaline flow of surface water from the GoAd into the RS against the prevailing northern winds during winter (8). A series of mesoscale eddies along the RS (9) increases the horizontal mixing. During June−September, the northeast monsoon is reversed toward southwest over the IO, inverting the direction of surface water flow in the northern IO, GoAd, and southern RS. The flow reversal induces intense upwelling and very high productivity along the western coasts of these regions (10). Surface wate...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.