Adsorption of methyl orange anionic dye on the prepared activated carbon from pine cone

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Novel activated carbon prepared from an agricultural waste, Stipa tenacissima, based on ZnCl2 activation—characterization and application to the removal of methylene blue

International audienceActivated carbon (AC) was prepared by means of a novel physiochemical activation method from low-cost biosorbent, agricultural waste (Stipa tenacissima fiber). A two-step pyrolysis was considered instead of a single-step pyrolysis, which involved zinc chloride for the first activation step and a steam mixture of water, CO2 and acetic acid for the second step. The obtained AC was tested as an adsorbent for the removal of a basic dye, Methylene blue (MB) from aqueous solutions. Batch experiments were conducted to examine the effect of the main parameters, such as the initial MB concentration, the pH, and the kinetic adsorption of this dye. Results showed that a pH value of 7 is favorable for the adsorption of MB. Rate constants of pseudo-first-order, pseudo-second-order, and intraparticle diffusion coefficient were calculated to analyze the dynamic of the adsorption process; they showed that adsorption kinetics followed a pseudo-second-order and an intraparticle diffusion model, while the two straight lines describing experimental data indicated that intraparticle diffusion was not the limiting mechanism for adsorption. Among the tested isotherm models, the Sips isotherm was found to be the most relevant to describe MB adsorption onto both activated and non-ACs with the best maximum adsorption capacity (Qm), 178.44 and 27.21 mg g−1, respectively. The negative values of ΔG° revealed that the adsorption process was spontaneous. The positive values of ΔH° and ΔS° showed the endothermic nature and an increase in disorder of MB molecules during the adsorption process, respectively. © 2016 Balaban Desalination Publications. All rights reserved

Electrical discharges influence on the dielectric properties of natural insulating oil

International audienceThe aim of this work is to characterize a natural ester insulating liquid based on measurements of the dielectric parameters versus frequency (Frequency Domain Spectroscopy). The tests were carried out on a non-inhibited olive oil having high water content and submitted to electrical discharges (from 100 to 1600 discharges). The results so obtained show a significant increase of the dielectric constant and a decrease of conductivity when the frequency is increased

Prediction study of structural, elastic and electronic properties of FeMP (M = Ti, Zr, Hf) compounds

First principles calculations are applied in the study of FeMP (M = Ti, Zr, Hf) compounds. We investigate the structural, elastic, mechanical and electronic properties by combining first-principles calculations with the CASTEP approach. For ideal polycrystalline FeMP (M = Ti, Zr, Hf) the shear modulus, Young’s modulus, Poisson’s ratio, elastic anisotropy indexes, Pugh’s criterion, elastic wave velocities and Debye temperature are also calculated from the single crystal elastic constants. The shear anisotropic factors and anisotropy are obtained from the single crystal elastic constants. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal. Keywords: FeTP, FeHfP, Electronic band structure, Bulk modul

Removal of the anionic dye Biebrich scarlet from water by adsorption to calcined and non-calcined Mg–Al layered double hydroxides

International audienceA native layered double hydroxide Mg–Al–CO3, denominated LDH, containing Mg(II) and Al(III) in the layers, was prepared by a co-precipitation method. Its calcined form Mg–Al, (CLDH), was obtained by calcination at 500°C. Both materials were characterized by powder X-ray diffraction (PXRD), Fourier transformation infrared spectroscopy, thermogravimetric analysis, and the determination of the point of zero charge. The porous structure of the solids was investigated by nitrogen adsorption at 77 K. The adsorptive affinity of these materials for Biebrich Scarlet was studied as a function of dye–adsorbent contact time, initial pH of the solution, initial dye concentration, and temperature. Sorption kinetics data fitted best to a pseudo-second-order model suggesting that the process of BS adsorption is controlled by reaction rate for interaction of dye molecules rather than by diffusion. Equilibrium data for both adsorbents were in accordance with both Sips and Langmuir isotherm models. The sorption capacity of CLDH was found to be almost independent on the initial pH, while sorption capacity of LDH was lower in neutral and alkaline conditions than at acidic pH. The adsorption process was also found to be spontaneous and endothermic in nature. © 2016 Balaban Desalination Publications. All rights reserved

Synthetic carbons from coffee grounds activated by phosphoric acid: surface chemistry and adsorption characteristics

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGF-4XK45HD-5&_user=1085808&_coverDate=03%2F15%2F2010&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_searchStrId=1680804541&_rerunOrigin=google&_acct=C000047619&_version=1&_urlVersion=0&_userid=1085808&md5=3d93f67aebe029e330dc8eeb3ade16a7&searchtype=aActivated carbons were prepared by the pyrolysis of coffee grounds impregnated by phosphoric acid at 450 °C for different impregnation ratios: 30, 60, 120 and 180 wt.%. Materials were characterized for their surface chemistry by elemental analysis, “Boehm titrations”, point of zero charge measurements, Infrared spectroscopy, thermogravimetric analysis (TGA); as well as for their porous and morphological structure by Scanning Electron Microscopy (SEM) and nitrogen adsorption at 77 K. The impregnation ratio was found to govern the porous structure of the prepared activated carbons. Low impregnation ratios (120 wt.%) yielded to essentially mesoporous carbons with specific surface areas as high as 925 m2 g−1, pore volume as large as 0.7 cm3 g−1, and neutral surface. The activated carbons prepared from coffee grounds were compared to a commercial activated carbon (SBET 1400 m2 g−1) for their adsorption isotherms of methylene blue and “Nylosan Red N-2RBL”, a cationic and anionic (azo) dye respectively. The mesoporous structure of the material produced at 180 wt.% H3PO4 ratio was found to be appropriate for an efficient sorption of the latter azo dye

Carbons prepared from coffee grounds by H3PO4 activation: Characterization and adsorption of methylene blue and Nylosan Red N-2RBL

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