Application of Poly( N -octyl-4-vinylpyridinium bromide) as an Efficient, Versatile, and Robust Sorbent for Chromate Removal from Different Water Matrixes

Abstract

Hexavalent chromium [Cr(VI)] remains a priority water contaminant due to its high toxicity, mobility, and persistence in complex aqueous environments, where conventional sorbents often exhibit limited selectivity and reusability. Here, poly(N-octyl-4-vinylpyridinium bromide) is evaluated as a versatile ion exchange platform for Cr(VI) removal under realistic water treatment conditions. Adsorption kinetics, thermodynamics, and equilibrium behavior indicate a spontaneous, exothermic, 1:1 anion-exchange process well described by a Langmuir model. Maximum adsorption capacities of 168.6 mg Cr(VI) g–1 in deionized water and 134.0 mg Cr(VI) g–1 in a natural river water matrix were obtained, demonstrating robustness against matrix effects and competing anions. Desorption using dilute NaOH enabled substantial material regeneration and reuse across repeated cycles. To enhance operational applicability, magnetic iron oxide nanoparticles were incorporated without compromising intrinsic adsorption performance, allowing rapid and quantitative sorbent recovery. In addition, nanofibrous membranes fabricated by blending the polyelectrolyte with polycaprolactone achieved >99.7% Cr(VI) removal under ultrafiltration pressure conditions in a cross-flow configuration. Overall, this work demonstrates a regenerable and adaptable polyelectrolyte-based platform capable of Cr(VI) abatement across batch, fixed-bed, and membrane configurations in real water matrixes, supporting its potential for practical water treatment applications.