Application of xanthine functionalized resin in speciation of chromium in natural water

Abstract

Separation and preconcentration of two forms of chromium viz. Cr III and Cr VI in natural water was carried out applying a resin containing xanthine moiety anchored onto polystyrene-divinylbenzene (8%) by azo (-N=N-) function. The maximum exchange capacity of Cr III was found to be 0.6718 mmol g -1 at pH 6.5 and that for Cr VI was 1.1324 mmol g -1 at pH 1.0. The sorption of both Cr III and Cr VI onto resin follows a second order kinetics with rate constant values of 0.047 and 0.410 mmol -1 min -1 for Cr111 and Cr VI respectively. The two species Cr III and Cr VI are eluted completely by 3 M and 4 M HCl respectively. The detection limits of 4.3 and 5.1 ng ml -1 for Cr III and Cr VI were achieved. The optimum flow rate, sample breakthrough volume of column operation for Cr III and Cr VI species were found to be 1.2 ml min -1 and 3000 ml respectively. Finally the developed method using this resin was applied for determination of these two species in synthetic binary mixtures, natural water samples and validated comparing with results using previously developed method.