pH dependent speciation and removal of chromium from environmental samples using a chelating resin containing derivatised L-methionine

pH dependent chemical speciation of inorganic chromium species and their removal from environmental samples have been performed on a chelating resin having N-(3-indolylmethyl) L-methionine moiety. The novelty of the resin is that it can bind both Cr-III and Cr-VI at two different pH. The maximum sorption capacity of the resin for Cr-III is 1.37 mmol g(-1) at pH 8.6 where no sorption of Cr-IV was observed. Again, maximum sorption of Cr-VI is 1.752 mmol g(-1) at pH 4.0 where sorption of Cr-III is almost nil. We have observed complete desorption of Cr-III and Cr-VI with 3.0 mol L-1 HCl and 4.0 mol L-1 HCl respectively. Detection limits (three times of the standard deviation for blank) for Cr-III and Cr-VI has been found as 0.4 mg mL(-1) and 1.3 mg mL(-1) respectively. Sorption of both Cr-III and Cr-VI has been found to follow a second order rate law. The developed method has been used for the chemical speciation and removal of chromium from different environmental samples and validated by standard/reference method. The concentration of chromium has been measured by flame atomic absorption spectrometer (FAAS).