Simple and selective extraction process for chromium (VI) in industrial wastewater

A simple and relatively green method has been developed for the determination of chromium based on the extraction of chromium (VI) as its ion-association complex with tetrabutylammoniumiodide (TBAI) in acidic medium. The ion-pair is extracted using isobutylmethylketone (MIBK) as the solvent. The concentration of the extracted chromium (VI) in the organic layer was measured spectrophotometrically at a wavelength maximum of 366 nm and the organic layer was characterized using FT-IR spectroscopy. The influence of various analytical parameters such as pH, aqueous phase volume, equilibration time, interfering ions etc. has been studied in detail. The extracted chromium (VI) was back extracted into the aqueous phase to the non-toxic chromium (III) using ascorbic acid. The calibration graph was linear in the range of 0-2 μg mL−1 chromium (VI) with a relative standard deviation of 2.4%. A detection limit of 0.25 μg in 25 mL aqueous phase volume could be achieved and the validity of the proposed method has been checked by applying it to synthetic mixtures, spiked water sample, electroplating wastewater and certified reference material BCR®-715.