Bamboo (Guadua chacoensis) Si-char (BC) and Magnetic Fe3O4/Si-char (BC-Fe) were prepared and used to treat arsenite (AsO33-) contaminated water. Toxicity of As(III) (inorganic) is significantly greater than As(V) and more difficult to remove from water. Removal efficiency was optimized verses pH (in both de-ionized water and lake water), contact time and initial concentration. Fixed-bed column sorption, sorption from complex matrices and regeneration (KOH and K3PO4) were also studied. Pseudo second order model best described the As(III) sorption for BC and BC-Fe, (R2= 0.99). The Langmuir isotherm showed the best fit at 25 °C with a 15.72 mg/g adsorption capacity which is comparable with other adsorbents, but with faster kinetics (~60 min) at pH 7 and ambient temperature. X-ray photoelectron spectroscopy (XPS) studies and arsenic speciation studies (LC-ICP-MS) showed the presence of As(III) and less toxic As(V) on the of Fe3O4 surface indicating oxidation upon contact or drying under oxic conditions and due to Fe(III) to Fe(II) magnetite oxidation of adsorbed (or adsorbing) As(III) under anoxic conditions. BC, BC-Fe and their As-laden analogues were extensively characterized using XPS, XRD, Mössbauer and XANES spectroscopy.

Sorption of As(III) using Fe3O4 nanoparticles dispersed on Guadua chacoensis bamboo Si-rich biochar (Si-char) and its redox transformations

ACS Fall 2021

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