Resumen

CEDENO, E. et al. In-situ monitoring by thermal lens microscopy of a photocatalytic reduction process of hexavalent chromium. Rev. mex. fis. [online]. 2018, vol.64, n.5, pp.507-511.  Epub 30-Nov-2019. ISSN 0035-001X.

In this work, we describe the application of a micro-spatial thermal lens spectroscopy setup (thermal lens microscope, TLM) with coaxial counter-propagating pump, and probe laser beams, and an integrated passive optical Fabry-Perot, to quantify the Cr-VI concentration in water during a photocatalytic reaction in-situ. A series of test samples was analyzed using the 1.5 diphenil carbazide colorimetric method. A calibration curve was obtained by plotting of the TLM signal as a function of the concentration of Cr(VI) in a range between 0 and 10 μg/L (1 𝜇g/L = 1 ppb, part per billion), with a detection limit of 53 ng/L (1 ng/L = 1 ppt, part per trillion). A solution of 10 𝜇g/L Cr(VI) in distillated water was placed into a cell in contact with an iron-incorporated titanium dioxide film, which was previously grown onto a 1 mm thick glass microscope slide by the sol-gel dip-coating technique. The TLM signal was registered as a function of the photocatalysis time measured from the beginning of the process, radiating the film with UV-violet light. The Cr(VI) concentration was determined with the calibration curve and after the first 50 minutes a reduction of 95 % of Cr(VI) was observed, being the chemical reaction kinetic described by a potential time decreasing function.

Palabras llave : Thermal lens microscopy; photocatalysis; hexavalent chromium; titanium dioxide; 42.62.Fi; 07.88.+y; 82.80.Kq.

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