Fast nitrate and fluoride adsorption and magnetic separation from water on α-Fe2O3 and Fe3O4 dispersed on Douglas fir biochar

alpha-Fe2O3 and Fe3O4 dispersed on high surface area (663m(2)/g) Douglas fir biochar (BC) was prepared for fast nitrate and fluoride ion removal from water using magnetic separations. This biochar, made originally at 900 degrees C, was impregnated with FeCl3 and converted by pyrolysis at 600 degrees C to magnetic (494m(2)/g) biochar (MBC). MBC and its precursor BC were characterized using SEM, SEM-EDX, STEM, SBET, PZC measurements, XRD analysis, and XPS. Dispersed alpha-Fe2O3 and Fe3O4 particles caused magnetization and generated most adsorption sites, causing more nitrate and fluoride uptake than BC. Both nitrate and fluoride adsorption on MBC remained high over a pH range from 2 to 10. Sorption was evaluated from 298 to 318 K using the Langmuir and Freundlich isotherm models. Langmuir adsorption capacities were 15 mg/g for nitrate and 9 mg/g for fluoride, higher capacities than those reported for other biochar and iron oxide adsorbents.