Solid phase extraction of bismuth and chromium by rice husk

A major agricultural waste, rice husk and its ash were used for the preconcentration and separation of bismuth and chromium prior to their determination by flame atomic absorption spectrometry (FAAS) and their sorption properties with respect to bismuth and chromium from water samples were investigated. For this purpose, rice husk was thermally treated at 300degreesC for one hour and 600degreesC for ten hours in a muffle furnace. The effects of various experimental conditions on retention and elution efficiencies of studied elements for untreated rice with husk, untreated and thermally treated rice husk were investigated by applying batch and column methods. The analyte elements were quantitatively collected on rice with husk, the untreated and thermally treated rice husk at 300degreesC if the pH is above 3. The analvte elements retained on the rice with husk, rice husk or its ash were completely recovered by means of 2.0 M hydrochloric acid. Maximum chromium adsorption capacities of untreated rice with husk (URH), rice husk (RH), rice husk ash heated at 300degreesC (RHA-300) and 600degreesC (RHA-600) are 0.12, 0.50, 19.09 and 6.49 mg Cr/g adsorbent, respectively and 0.47, 294, 18.34 and 4.90 mgBi/g adsorbent, respectively. When RHA-300 was used which is the most suitable adsorbent of all, detection limits (3 delta) were 13 mug/L for Bi and 1.5 mug/L for Cr. The relative standard deviations for the determinations were found to be 1.0-7.9%. The results showed that RHA especially heated at 300degreesC could be used as an efficient and cheap adsorbent for the removal of some heavy metals from the natural water samples and for the preconcentration and separation of bismuth and chromium prior to their determination by flame atomic absorption spectrometry.