Study of Cr(VI) reduction by activated carbon using high resolution X-ray emission spectroscopy

A.N. MÓDENES; F.R. ESPINOZA QUIÑONES; S.M. PALACIO; G. STUTZ; G. TIRAO; A.S. CÂMERA

Campinas

Congreso; XX Reunión Anual de Usuarios del LNLS; 2010

In this work granular activated carbon has been chosen as an absorbent in or-der to investigate the Cr(VI) reduced by adsorption experiments. Several batchchromium-sorption experiments were carried out using 0.25 g of granular activatedcarbon into 50 mL metal solution containing approximately 70 and 140 mg L−1of Cr(VI) and Cr(III), respectively. Batch experiments at 3.5 pH were carried outto determine the chromium ions sorption capacity and to verify the Cr(VI) reduc-tion. A set of 100 mg Cr treated sample pellets was prepared. Measurements of thewhole Cr-K X-ray emission spectra were performed using a combination of a high-resolution Johann-type spectrometer and a high flux, 6.1-keV X-ray monochromaticbeam at the D12A-XRD1 beamline at the Brazilian Synchrotron Light Laboratory.Sample, spherically focusing nearly backdiffracting Si(111) crystal analyzer and sil-icon pin-diode detector were positioned on the Rowland circle to fulfill the focusingcondition in a vacuum chamber. Cr-K satellite lines have been characterized forall K spectra of Cr ions treated material the. Based on the energy position andintensity of Cr-K satellite lines, activated carbon and non-living aquatic macro-phytes roots were found to act mainly as good adsorbents, reducing first Cr(VI) toCr(III), followed by the Cr(III) adsorption. Thus, HR-XRF technique has allowedverifying that the adsorption process is responsible by the Cr(VI) reduction andremoval from metal solutions.