Nano-sized adsorbents have been studied to implement efficient water treatment technologies based on their distinctive properties. Arsenic is a substantial environmental concern metalloid due to its toxicity. Fe(III) incorporated rice husk hybrid biochar was synthesized by one-step slow pyrolysis at 600°C for 1h to remediate As(V) from wastewater. This magnetic biochar/Fe3O4/α-Fe2O3 composite was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by X-ray (SEM-EDX), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Brunauer−Emmett−Teller (BET) surface area techniques, point of zero charge analysis (PZC) and elemental analysis. As(V) sorption was optimized versus the pH, adsorbent/adsorbate contact time, initial adsorbate concentration, and temperature. pH 5 was selected as the optimized pH for As(V) adsorption due to low iron leaching and related to the natural water. This nano-sized iron oxide-formed rice husk biochar has shown enhanced adsorption capacity than unmodified biochar. Adsorption kinetics data were interpreted with the pseudo-second-order model, and sorption equilibriums were reached after 3h for 0.5 mg/L and within 2h for 5 and 50 mg/L initial As(V) concentrations. The As(V) sorption isotherm studies were carried out at 5°C, 25°C, and 40°C for As(V) 0.25-250 mg/L initial concentrations. Sorption was endothermic and clearly described by the Langmuir isotherm model with a 5.56 mg/g maximum adsorption capacity at 25°C. The effect of competitive ions (at 0.01, 0.1, and 1 mM initial concentrations of PO43-, MoO42-, CO32-, CrO42- , SeO42-, Cl- and F- ) on As(V) removal were studied. Batch regeneration of this adsorbent was successfully evaluated over three cycles with 1 M NaOH as the stripping agent. The material was applied to different water matrices to determine its robustness.

Remediation of aqueous As(V) by adsorption onto Fe(III) impregnated rice husk biochar

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