Modified Sagnac interferometer for contact-free length measurement of a direct absorption cell

International audienceAccurate path length measurements in absorption cells are recurrent requirements in quantitative molecular absorption spectroscopy. A new twin path laser interferometer for length measurements in a simple direct path absorption geometry is presented, along with a full uncertainty budget. The path in an absorption cell is determined by measuring the optical path length change due to the diminution of the refractive index when the cell originally filled with nitrogen gas is evacuated. The performance of the instrument based on a stabilized HeNe laser is verified by comparison with the results of direct mechanical length measurements of a roughly 45 mm long, specially designed absorption cell

Scale offset for frequency tracker

A new method for wide frequency laser control is presented. A laser with P and S polarizations and an ultra-stable ULE made Fabry-Pérot interferometer (FP) are used to lock alternatively a laser frequency from one FP signal to the other by the mean of two acousto-optic modulators (AOM). The stability of the FP is by this way transferred to the laser. The servo-locking system overcome the free spectral range limit by switching from one Airy function to the second one. As the method covers as many free spectral range as desired, the laser frequency can be driven all over the laser gain curve. Experimental setup and resolutions expected of the instrument are discussed

Performance of a novel twin interferometer for contact-free length measurement of absorption cells

International audienceAccurate path length measurements in absorption cells are recurrent requirements in quantitative molecular absorption spectroscopy . Strongly absorbing sub- stances (σ ~ 10-17 cm2), such as ozone, or aromatic compounds require lengths to be measured with uncertainties at about 100 μm or better if their absorption cross sections are to be determined with sub per mil accuracy.Here, we present the development of a new interferometer for the refractometric measurement of cell lengths with an expanded standard uncertainty (k = 2) of 16 μm. The apparatus is used for length and index measurements

Performance of a novel twin interferometer for contact-free length measurement of absorption cells

International audienceAccurate path length measurements in absorption cells are recurrent requirements in quantitative molecular absorption spectroscopy . Strongly absorbing sub- stances (σ ~ 10-17 cm2), such as ozone, or aromatic compounds require lengths to be measured with uncertainties at about 100 μm or better if their absorption cross sections are to be determined with sub per mil accuracy.Here, we present the development of a new interferometer for the refractometric measurement of cell lengths with an expanded standard uncertainty (k = 2) of 16 μm. The apparatus is used for length and index measurements

Quaternized triethanolamine-sebacoyl moieties in highly branched polymer architecture as a host for the entrapment of acid dyes in aqueous solutions

This paper reports the synthesis of a hyperbranched polymer by a cost-effective one-step copolymerization of A3 and B2 monomers, namely, triethanolamine and sebacoyl chloride, respectively, followed by methylation of tertiary amine groups. The structure of the hyperbranched polymer QTEAS as an efficient material for the removal of acid dyes was demonstrated by Fourier transform infrared spectroscopy (FTIR), cross polarization magic angle spinning (CPMAS) 13C NMR, thermogravimetric analysis (TGA), powder X-ray diffraction (DRX) and scanning electron microscopy (SEM). The removal of indigo carmine (IC) and Evans blue (EB) was expected to be driven by the electrostatic attraction between positively charged quaternary ammonium groups within the hyperbranched polymer and the negatively charged dyes. The removal process was found to be closely connected to the total number of sulfonate groups on the surface of the dyes. Nonetheless, the ionic strength does not affect the dyes' removal efficiency by the hyperbranched polymer. The sorption capacities at saturation of the monolayer qmax were determined to be 213.22 mg g−1 and 214.13 mg g−1, for IC and EB, respectively, thus showing the greater affinity of QTEAS sorbent for both dyes. Despite its extended molecular structure, EB is removed with the same effectiveness as IC. Finally, the great efficiency of the highly branched polymer for dye removal from colored wastewater was clearly demonstrated

Alkaline treatment of timber sawdust: A straightforward route toward effective low-cost adsorbent for the enhanced removal of basic dyes from aqueous solutions

The present study assesses the ability of two low-cost adsorbents – timber sawdust (TS–OH) and its alkaline treated analog (TS–ONa) – to remove two basic dyes, namely, Methylene Blue and Methyl Green, from aqueous solutions. The presence of new functional groups on the surface of TS–ONa resulted in a dramatic increase of surface polarity and the density of sorption sites, thereby improving the sorption efficiency of the cationic dyes. The results obtained from the sorption characteristics have revealed that the sorption process for TS–ONa was uniform and rapid. The adsorption of cationic dyes reached equilibrium within the first 10 min of contact time and the treated material acts efficiently in a wide pH range of dye solutions. The extent of adsorption was measured through equilibrium sorption isotherms and analyzed using the Langmuir model. The monolayer saturation capacities for Methylene Blue are 694.44 and 1928.31 mg g−1 and for Methyl Green are 892.86 and 1821.33 mg g−1 for TS–OH and TS–ONa, respectively. Therefore, the chemically treated sawdust proved two- to threefold higher adsorption capacities of these dyes than those of the untreated analog. The exothermic nature of adsorption is demonstrated by a decrease of adsorption capacity with increasing temperature, and the negative value of free energy change indicated the spontaneity of adsorption. Desorption experiments with 1 M aqueous NaCl put into evidence that cationic dyes were completely desorbed from the matrices and the reusability of the TS–ONa matrix after three repeated cycles led to just a slight attenuation in its performance. These results show that alkaline treatment of a low value by-product of the timber industry leads to a powerful and efficient low-cost adsorbent, which may be used for the treatment of colored wastewaters

Nonlinear Frequency-Sweep Correction of Tunable Electromagnetic Sources

International audienc

Alkaline treatment of timber sawdust: A straightforward route toward effective low-cost adsorbent for the enhanced removal of basic dyes from aqueous solutions

International audienceThe present study assesses the ability of two low-cost adsorbents - timber sawdust (TS- OH) and its alkaline treated analog (TS-ONa) - to remove two basic dyes, namely, Methylene Blue and Methyl Green, from aqueous solutions. The presence of new functional groups on the surface of TS-ONa resulted in a dramatic increase of surface polarity and the density of sorption sites, thereby improving the sorption efficiency of the cationic dyes. The results obtained from the sorp- tion characteristics have revealed that the sorption process for TS-ONa was uniform and rapid. The adsorption of cationic dyes reached equilibrium within the first 10 min of contact time and the trea- ted material acts efficiently in a wide pH range of dye solutions. The extent of adsorption was mea- sured through equilibrium sorption isotherms and analyzed using the Langmuir model. The monolayer saturation capacities for Methylene Blue are 694.44 and 1928.31 mg/g and for Methyl Green are 892.86 and 1821.33 mg/g for TS-OH and TS-ONa, respectively. Therefore, the chem- ically treated sawdust proved two- to threefold higher adsorption capacities of these dyes than those of the untreated analog. The exothermic nature of adsorption is demonstrated by a decrease of adsorption capacity with increasing temperature, and the negative value of free energy change indi- cated the spontaneity of adsorption. Desorption experiments with 1 M aqueous NaCl put into evi- dence that cationic dyes were completely desorbed from the matrices and the reusability of the TS- ONa matrix after three repeated cycles led to just a slight attenuation in its performance. These results show that alkaline treatment of a low value by-product of the timber industry leads to a powerful and efficient low-cost adsorbent, which may be used for the treatment of colored waste- waters