In-situ monitoring by thermal lens microscopy of a photocatalytic reduction process of hexavalent chromium

• E. Cedeño ^[2] ; J. Plazas-Saldaña ^[1] ; F. Gordillo-Delgado ^[1] ; A. Bedoya ^[2] ; E. Marín ^[2]
  1. [1] Universidad del Quindío

     Universidad del Quindío

     Colombia

     
  2. [2] Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Ciudad de México, México
• Localización: Revista Mexicana de Física, ISSN-e 0035-001X, Vol. 64, Nº. 5, 2018, págs. 507-511
• Idioma: inglés
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• Resumen

  • 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.