Highly efficient As(III) removal in water using millimeter-sized porous granular MgO-biochar with high adsorption capacity

Biochar adsorbents for removing As(III) suffer from the problems of low adsorption capacity and ineffective removal. Herein, a granular MgO-embedded biochar (g-MgO-Bc) adsorbent is fabricated in the form of millimeter-sized particles through a simple gelation-calcination method using chitosan as biochar sources. Highdensity MgO nanoparticles are evenly dispersed throughout the biochar matrix and can be fully exposed to As(III) through the rich pores in g-MgO-Bc. These features endow the adsorbent with a high adsorption capacity of 249.1 mg/g for As(III). The g-MgO-Bc can efficiently remove As(III) over a wide pH of 3-10. The coexisting carbonate, nitrate, sulfate, silicate, and humic acid exert a negligible influence on As(III) removal. 300 mu g/L of As (III) can be purified to far below 10 mu g/L using only 0.3 g/L g-MgO-Bc. The spent g-MgO-Bc could be well regenerated by simple calcination. In fixed-bed column experiments, the effective treatment volume of As(III)spiked groundwater achieves 1500 BV (30 L) (3 g of adsorbent, solution flow rate of 2.0 mL/min, C0 = 50 mu g/L). The Mg(OH)2 generated in situ in g-MgO-Bc is responsible for the adsorption of As(III) through the innersphere complex mechanism. The work would extend the potential applicability of biochar adsorbent for As(III) removal to a great extent.

Automated summary

A granular MgO-embedded biochar adsorbent, g-MgO-Bc, with high adsorption capacity of 249.1 mg/g for As(III) is fabricated by dispersing high-density MgO nanoparticles throughout the biochar matrix. The adsorbent can efficiently remove As(III) over a wide pH range and be regenerated easily through simple calcination. This work extends the potential applicability of biochar adsorbents for As(III) removal.