High-performance towards Cr(VI) removal using multi-active sites of polypyrrole–graphene oxide nanocomposites: Batch and column studies

Abstract

Hexavalent chromium [Cr(VI)] adsorption onto polypyrrole graphene oxide nanocomposite (PPy–GO NC) From aqueous solutions was explored using batch and packed-bed column modes. The performance of the PPy–GO NC for Cr(VI) removal was evaluated as a function of solution pH, initial Cr(VI) concentration, temperature, bed mass and time. The characterization of PPy–GO NC using HR-TEM, FE-SEM and Raman spectroscopy confirmed that graphite was successfully exfoliated to thin layered graphene sheets and also ensured the presence of the PPy in the PPy–GO NC. Meanwhile the zeta potential data showed that the point of zero charge of the nanocomposite was at pH 6.2. Batch sorption isotherm data at optimum solution pH of 2, was satisfactorily described by the Langmuir isotherm model with a maximum sorption capacity of 625mg/g at 25°C, while the kinetic data fitted well with the pseudo second order kinetic model. Sorption of Cr(VI) onto PPy–GO NC in binary ions systems was also evaluated and results showed that the presence of co-existing ions had no effect on Cr(VI) removal. Expressed through breakthrough curves, the packed-bed Cr(VI) sorption data showed consistency with the ideal s-shape. Moreover, a large volume of Cr(VI) contaminated water (64.08L) was successfully treated to below allowable discharge limit at low influent Cr(VI) concentration (10mg/L) using 2g of PPy–GO NC at a flow rate of 3mL/min. Breakthrough data were successfully described by the Thomas and Yoon–Nelson models.