Adsorption columns for the removal of hazardous hexavalent chromium, arsenite and fluoride ions from aqueous media by novel N, P - doped graphene oxide/chitosan composites

Heavy metal and fluoride contamination in wastewater is a major concern for both people and the environment. This has necessitated the use of effective and sustainable removal technologies. Adsorption is the most prevalent technology because of its flexibility, simplicity, and cost-effectiveness. This study suggests the application of chitosan (Cs) and phosphorous‑nitrogen (P,N) co-doped graphene oxide (GO) composite beads for the removal of Cr(VI), As(III) and F − , evaluating it both in batch and column studies. The materials were characterized using Scanning Electron Microscopy (SEM), N 2 porosimetry, X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR), while also testing their mechanical properties, swelling and stability over a wide range of pH. The adsorption evaluation showed that Cs/P,N-GO can effectively remove up to 1.47 mg/g, 128.55 mg/g and 127.76 mg/g of As(III), Cr(VI) and F − , respectively, at pH 3 using 0.5 g/L of the beads. The kinetic data were described well by pseudo-second-order (PSO) and intra-particle diffusion (IPD) models, indicating chemisorption and intra-particle diffusion, while Toth and Freundlich fit the isothermal data better. Thermodynamic data showed that the process was endothermic and spontaneous. Lastly, reusability studies revealed that the beads can be used for up to 10 cycles, with a ~ 10% loss in their initial performance for all 3 studied ions. • P,N co-doped GO/Chitosan beads were evaluated for Cr(VI), As(III) and F − removal. • Cs/P,N-GO beads showed good reusability and stability. • Extensive column studies under various conditions were performed. • Cs/P,N-GO performance was evaluated towards coexisting ions and real wastewater.