Magnetic Fe3O4/Douglas fir biochar composites were prepared with a 29.2% wt. Fe3O4 loading and used to treat arsenite-contaminated water. Removal efficiency was optimized verses pH, contact time and initial concentration. Column sorption and regeneration were also studied. Adsorption kinetics data fit best the pseudo second order model (R2&gt;0.99). Adsorption was analyzed with seven isotherm models at 20°C, 25°C and 40°C. The Sips isotherm showed the best fit at 25°C with a 5.06 mg/g adsorption capacity which is comparable with other adsorbents, but with faster kinetics (~1-1.5 h) at pH 7 and ambient temperature. The Gibbs free energy (ΔG) of this spontaneous As(III) adsorption was -5.38 kJ/mol and ΔH = 88.46 kJ/mol was endothermic. Experiments were performed on industrial and laboratory wastewater samples in the presence of other co-existing contaminants (pharmaceutical residues, heavy metals ions and oxi-anions). The composite reduced the arsenic concentrations below the WHO’s safe limit of 0.2 mg/L for waste water discharge. X-ray photoelectron spectroscopy (XPS) studies 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. pH-dependent surface complexation was proposed as the governing adsorption mechanism.

Removal of Arsenic from water using iron oxide precipitated Douglas fir biochar

2019 Spring National Meeting

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