Molecular weight effect on chromium(VI) retention by poly(N-octyl-4-vinylpyridinium bromide) copolymers

Abstract

Copolymers containing poly(4-vinylpyridine) (P4VP) quaternized with octylbromide (C8Br) were synthesized. The rate of quaternization was determined using conductivity measurements and confirmed by 1 H NMR spectroscopy. We describe the effect of P4VP molecular weight on the retention ability of hexavalent chromium (Cr(VI)). The retention of Cr(VI) was investigated by batch equilibrium procedure, and this study was monitoring by UV‐vis spectrophotometry and FTIR spectroscopy. Empirical equation expressing the adsorbent amount as a function of molecular weight was proposed for the retention of Cr(VI). Four P4VP samples were considered in a wide interval of molecular weights: 7.5 � 10 3 ‐9.4 � 10 5 g/mol. The retention efficiency increases with copolymer molecular weight of P4VP then remains constant for long chain from Mw=3.8 � 10 5 g/mol. The adsorption kinetic experiments reveal that the adsorbed amount of Cr(VI) continuously increases with the time and reaches saturation after 10min, independently to the molecular weight. P4VP-C8Br showed fairly good results in total chromium removal kinetics.