A pH- and temperature-responsive magnetic adsorbent poly(N-isopropylacrylamide) grafted chitosan/Fe3O4 composite particles, CN-MCP, was synthesized for the removal of the endocrine-disrupting ...chemical nonylphenol. According to the structural characteristics (changeable surface-charge and hydrophilic/hydrophobic properties) of the targeted contaminant, CN-MCP was designed owning special structure (pH- and temperature-responsiveness for the changeable surface-charge and adjustable hydrophilic/hydrophobic properties, respectively). Compared to chitosan magnetic composite particles without grafting modification (CS-MCP) and several other reported adsorbents, CN-MCP exhibited relatively high adsorption capacity for nonylphenol under corresponding optimal conditions (123 mg/g at pH 9 and 20 °C; 116 mg/g at pH 5 and 40 °C). Meanwhile, high selectivity of the novel adsorbent in selective adsorption of nonylphenol from bisolute solution of nonylphenol and phenol was found. Effects of grafting ratio of the grafted polymer branches and coexisting inorganic salts on the adsorption were systematically investigated. Moreover, CN-MCP demonstrated desired reusability during 20 times of adsorption–desorption recycling. The high adsorption capacity, high selectivity, and desired reusability aforementioned revealed the significant application potential of CN-MCP in the removal of NP. On the basis of the adsorption behaviors, isotherms equilibrium, thermodynamics and kinetics studies, and instrumental analyses including X-ray photoelectron spectroscopy, BET specific surface area, zeta potential, and static water contact angle measurements, distinct adsorption mechanisms were found under various conditions: charge attraction between CN-MCP and the contaminant, as well as binding between polymeric branches of CN-MCP and nonyls, contributed to the adsorption at pH 9 and 20 °C; whereas hydrophobic interaction between CN-MCP and nonylphenol played a dominant role at pH 5 and 40 °C. The current study provided a strategy for the structural design of adsorbents according to the features of targeted emerging contaminants, and the continuity of the work was discussed and proposed.
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•Chitosan-based magnetic composite particles with core-brush topology are synthesized.•These particles have improved surface areas resulting from core-brush topology.•These particles ...have high adsorption efficiency in the removal of diclofenac sodium.•CD-MCP with polycationic brushes displays the highest adsorption capacities.•Charge attraction was the intrinsic driving force promoting adsorption.
A series of magnetic composite adsorbents with core-brush topology were prepared through grafting co-polymerization on the surface of chitosan/Fe3O4 composite particles (CS-MCP), and then applied for the removal of two pharmaceuticals (diclofenac sodium (DCF) and tetracycline hydrochloride) from water. Adsorption performance evaluation, including adsorption capacities from single- and binary-solute solutions at different pHs, influences of coexisting salts, desorption and reusability, demonstrated CD-MCP with polycationic brushes was a cost-effective adsorbent for DCF removal: Compared to CS-MCP, all the modified MCPs exhibited higher removal efficiencies, due to the enhanced surface areas resulting from core-brush topology; Among the modified MCPs with different surface charges, CD-MCP displayed the highest adsorption capacities, attributed to the electrostatic attraction between the positively charged brushes and the anionic contaminant’s species. Adsorption mechanism was investigated from both the macroscopic (thermodynamics and kinetics) and microscopic (changes of solution pH and spectral analyses of the adsorbent after adsorption) viewpoints: Charge attraction was the intrinsic driving force; A monolayer coverage of pharmaceuticals were adsorbed onto the brushes of CD-MCP; OH− exerted competitive adsorption effect; After adsorption, the originally extended polycationic brushes turned collapsed. The current study provided a strategy for the design of adsorbents from both topological and chemical structures.
The aromatic rings-functionalized chitosan-based flocculant (BDAT-CTS) exhibits enhanced removal efficiency in the flocculation of binary contaminants of Cu(II) and tetracycline. Display omitted
•An ...aromatic rings-functionalized chitosan-based flocculant (BDAT-CTS) is synthesized.•BDAT-CTS exerts enhanced interaction with the antibiotic (tetracycline, TC).•BDAT-CTS has high efficiency in the removal of binary contaminants of Cu(II) and TC.•Pairwise interactions among BDAT-CTS, Cu(II) and TC contribute to the flocculation.•π–π stacking is the main interaction between BDAT-CTS and TC.
Weak interaction between flocculants and antibiotics is a limitation in the flocculation of combined contaminants of heavy metals and antibiotics. To solve this problem, a novel chitosan-based flocculant (BDAT-CTS) owning functional groups of aromatic rings, which possessed potential to interact with other aromatic rings in antibiotics, was synthesized and applied to remove Cu(II) and tetracycline (TC) from water. Effects of pH, flocculant dosage and initial contaminant concentration were studied in detail. In comparison with previous reported chitosan-based flocculant without aromatic rings structure, BDAT-CTS enjoyed significantly enhanced removal efficiency in the treatment of binary contaminants. The highest removal efficiencies of TC and Cu(II) could reach to 98.8% and 94.0%, respectively, under the corresponding optimal conditions. The improved performance was attributed to the strong triangle pairwise interactions among BDAT-CTS, Cu(II) and TC according to flocculation mechanism investigation: besides charge attraction and coordination of BDAT-CTS–Cu(II), and coordination of Cu(II)–TC, there also exists π–π stacking between the triazine rings in BDAT-CTS and the aromatic rings in TC. The current work provided valuable guidance in the design of eco-friendly polymeric flocculants in the treatment of combined water contamination of heavy metals and antibiotics.
Cu(II) played the “bridge” role in promoting antibiotic removal due to strong coordination effect, whereas Zn(II) could not, when MAC was applied as the flocculant. Display omitted
•Cu(II) plays a ...“bridge” role in promoting removal of antibiotics, but Zn(II) cannot.•One factor for the “bridge” role is tightly binding of flocculant–heavy metals.•The other key factor is strong coordination of heavy metals–antibiotics.•Hard–Soft-Acid–Base theory and steric effect determine the coordination intensity.
Previous research found that certain types of heavy metals could play a “bridge” role in promoting removal of antibiotics in flocculation, but details (i.e. under what conditions and how heavy metals wielded this effect) were not clear. To investigate this point, two sorts of combined pollution Cu(II)–tetracycline and Zn(II)–sulfadiazine were selected in synthetic wastewaters for flocculation, to give a comparative study. A flocculant with high capacity to coordinate with heavy metals was applied. The flocculation performance declared that, Cu(II) improved removal of coexisted antibiotic molecules whereas Zn(II) did not. Analyses of macro- and micro-scopic properties of flocs demonstrated that, (i) tightly binding of the flocculant with heavy metals, and (ii) strong coordination of heavy metals–antibiotics when the two contaminants were suitably matched according to Hard–Soft-Acid–Base theory and steric effect, were two factors for heavy metals to perform the “bridge” role, and to achieve high co-removal efficiencies of both contaminants. The finding had operational significance for both promoted removal of antibiotics with the coexistence of heavy metals and mutual promotion in the removal of the combined contaminants from water.
Aircraft observations of cirrus cloud were made near Coffeyville, Kansas, during November 1991 as part of the First ISCCP Regional Experiment II (FIRE II) project. Cloud ice particle spectra ...measurements were made using both a particle measuring system (PMS) 2DC probe and an ice particle replicator. Particles larger than 200 micrometers were column rosettes. The replicator shows the presence of large numbers of ice crystals smaller than 66 micrometers (two PMS size bins) that are not recorded by the PMS 2DC probe. Calculations based on the replicator data of the geometrical blocked area and absorption cross section of the cloud per unit volume show that small particles can contribute significantly to and sometimes dominate both the solar extinction and the infrared emission. Intercomparison is made of the ice particle size, area, and mass distributions determined by these different instruments. Power law relationships for area occluded by a crystal as a function of crystal maximum dimension were computed from the PMS 2DC data. The wavelength-dependent infrared absorption cross section per volume was computed using a simple model based on anomalous diffraction and area and mass dimensional relationships for the ice crystals.
Experiments reveal complicated charging behavior during evaporation and vapor growth of ice and water in air. In the laboratory environment, the ice specimen acquires a positive charge during growth ...and a negative charge during evaporation, except in the temperature region between −4°C and 0°C, where ice behaves like water, acquiring a negative charge during condensation growth. The current is in excess of 10−16 amps cm−2 s−1. The ion concentration in the air has a strong effect on the charging direction. The analysis shows that the charging direction is not simply the result of evaporation or growth as suggested in earlier work but is determined by the properties of the charge carriers in ice (or water) and in the air. The new hypothesis can explain the charging behavior of both the growth of ice and water from the vapor and also evaporation observed in the present experiments. This new hypothesis also gives interpretation of some discrepancies in the earlier studies. The mechanism does not require absolute growth or evaporation to operate, and it is possibly an important contributory factor in charge separation both in thunderstorms and weakly electrified clouds when long growth or evaporation times are available.
Experiments reveal complicated charging behavior during evaporation and vapor growth of ice and water in air. In the laboratory environment, the ice specimen acquires a positive charge during growth ...and a negative charge during evaporation, except in the temperature region between -4 C and 0 C, where ice behaves like water, acquiring a negative charge during condensation growth. The current is in excess of 10 exp -16 amps /sq cm per sec. The ion concentration in the air has a strong effect on the charging direction. The analysis shows that the charging direction is not simply the result of evaporation or growth as suggested in earlier work, but is determined by the properties of the charge carriers in ice (or water) and in the air. The new hypothesis can explain the charging behavior of both the growth of ice and water from the vapor and also evaporation observed in the present experiments. This new hypothesis also gives interpretation of some discrepancies in the earlier studies. (Author)
PM10 Dispersion Modeling for Treasure Valley, Idaho Koracin, Darko; Podnar, Domagoj; Chow, Judith ...
Journal of the Air & Waste Management Association (1995),
08/2000, Letnik:
50, Številka:
8
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The recorded exceedances of the 24-hr PM
10
National Ambient Air Quality Standard (NAAQS) in Treasure Valley, Idaho, have been associated with prolonged stagnation periods during the winter. A ...comprehensive modeling study of PM
10
impact in Treasure Valley was performed to support the State Implementation Plan (SIP). The study included base-year and short-term episodic conditions. The ISCST3 (Industrial Source Complex Short Term 3) model, using the base-year meteorology and gridded emissions of mobile sources, point sources, and wood burning as input, generally agreed well with measurements in both temporal patterns and annual averages. The WYNDvalley model was evaluated using monitoring data and was used to simulate the PM
10
impact for episodic exceedances during stagnant winter conditions. An emission inventory was prepared for a base year (1995) and then extrapolated to the years 2000, 2005, 2010, and 2015 in order to determine air quality planning requirements. According to the simulations using base-year emissions and meteorology, exceedances are not expected. However, exceedances at some stations could be expected using projected emissions and episodic meteorology. Results from emission control strategies we developed indicate that mobile-source emissions have the most significant impact; reduction of 25% would be needed to eliminate the simulated exceedances in all projected years.
A model that predicts the evolution of bimodal size spectra in cirrus clouds is described. It was developed by predicting two size distributions: one for ice particles less than about 150 micro m and ...another for larger particles.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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