A novel graphene oxide–microalgae hybrid material for the removal of pentavalent arsenic from natural water and industrial wastewater

In this study, a hybrid bionanomaterial (GO@Di) composed of Dictyosphaerium sp. microalgae and graphene oxide (GO) was synthesized for the first time to be used as an adsorbent for the removal of pentavalent arsenic (As(V)) from aqueous solutions. GO@Di was characterized by analytical techniques including Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), pH at point of zero charge (pH_PZC), and BET surface analysis. Solution pH, adsorbent mass, initial concentration of the pollutant, and ionic strength were evaluated and optimized to identify the best conditions for As(V) removal using GO@Di. A removal efficiency of 69% and an adsorption capacity of 885 mg g⁻¹ were obtained under the optimal conditions of pH 3, 1 mg of GO@Di and initial As(V) concentration of 50 mg L⁻¹. The adsorption kinetics were also analyzed, reaching the equilibrium at 120 min. The experimental kinetic results were correlated with the pseudo-second order model. Equilibrium data were fitted with the Brunauer–Emmett–Teller (BET) isotherm model. Regeneration studies indicated that GO@Di could be re-used efficiently up to 4 adsorption/desorption cycles. Finally, GO@Di was applied to real samples of natural waters and industrial effluents, obtaining removal percentages between 52 and 95%, which demonstrated the promising potential of GO@Di to depollute complex aqueous matrices containing As(V). Future studies will focus on the removal of other arsenical species using GO@Di and its implementation in dynamic adsorption systems.