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Activated carbons were obtained from water hyacinth stems using K 2 CO 3 as activation agent, varying the impregnation time and the activation temperature and time, accordingly to a 2 3 factorial experimental design. The produced carbons showed activation yields (8-20%), alkaline point of zero charge (average of 9.5), methylene blue indexes from 264 to 893 m 2 /g, carboxylic surface groups in major proportion and graphitization degree from 4.01 to 6.27%. According to the statistical analysis, the activation temperature was significant for the yield and the methylene blue index. Activated carbon, labeled as AC5, was selected to assessing the naproxen adsorption in aqueous solution. Batch experiments yielded maximum adsorption capacity of 77.44% at pH ≈ 10.3, and contact time of 8 hr at initial concentration of 40 mg/g. The adsorption kinetics, isotherm model, and diffusion mechanism were described by the pseudo-second order model, the Redlich-Peterson equation and the film diffusion, respectively. K E Y W O R D S activated carbon, adsorption properties, naproxen adsorption, water hyacinth, experimental design

Amorphous carbon nitride films with N/C ratios ranging from 2.24 to 3.26 were deposited by reactive sputtering at room temperature on corning glass, silicon, and quartz as substrates. The average chemical composition of the films was obtained from the semiquantitative energy dispersive spectroscopy analysis. Photoluminescence measurements were performed to determine the optical band gap of the films. The photoluminescence spectra displayed two peaks: one associated with the substrate and the other associated withCNxfilms located at ≈2.13±0.02 eV. Results show an increase in the optical band gap from 2.11 to 2.15 eV associated with the increase in the N/C ratio. Raman spectroscopy measurements showed a dominantDband.ID/IGratio reaches a maximum value for N/C ≈ 3.03 when the optical band gap is 2.12 eV. Features observed by the photoluminescence and Raman studies have been associated with the increase in the carbon sp2/sp3ratio due to presence of high nitrogen content.

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