Iron oxide impregnated Pongamia pinnata microporous biochar composite as an effective bio-adsorbent for the remediation of arsenic ions from water

A hull of Pongamia pinnata (PP) is the waste generated during the production of biodiesel from its seed. In this study, a facile method was developed and applied to synthesize low-cost magnetic bio-adsorbent from the seed hull of PP for the mitigation of arsenic from water. A magnetic property was imposed by impregnating Fe3O4 nanoparticles into the biochar. This magnetic property of Magnetic Pongamia pinnata (MPP) makes it easy to separate adsorbent after adsorption with arsenic ions. The prepared bio-adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The batch adsorption results suggested that the optimal values for adsorbent dosages (200 mg L-1), pH (7.0 +/- 0.5), initial concentration in both the form of arsenic ions (0.5 mg L-1), and contact time (45 min) were determined in the adsorption process. The experimental value follows well with the Langmuir isotherm with a high determination coefficient (R-2 > 0.99) than the other models. The maximum Langmuir adsorption capacity for As(III) and As(V) was 13.87 mg g(-1) and 10.29 mg g(-1), which are consistent with the experimental capacity of 13.20 mg g(-1) and 10.19 mg g(-1), respectively. Therefore, the modification of Pongamia pinnata biochar provides an effective alternative adsorbent for arsenic removal in various environmental circumstances.