Efficient sorption of As(III) from water by magnetite decorated porous carbon extracted from a biowaste material

Arsenic is a highly toxic metal that causes cancer even at a low concentration and its removal from water resources is challenging. Herein, carbon extracted from waste onion bulbs is activated to cater for porosity and functionalized with magnetite (Fe3O4) nanoparticles (named MCK6) to address the challenge of As(III) removal. Synthesized MCK6 was highly mesoporous having a surface area of 208 m2/g, where magnetite nanoparticles (≤ 10 nm) are homogeneously distributed within a porous network. The developed adsorbent inherited functional groups from the biosource and magnetic property from magnetite making it ideal for removal of As(III). Further, MCK6 showed a maximum monolayer adsorption capacity (qm) of 10.2 mg/g at 298 K and pH 7. The adsorption thermodynamics delineates a non-spontaneous and endothermic reaction, where the kinetics followed pseudo 2nd order (R2 value of 0.977), while monolayer formation is explained by the Langmuir model. Moreover, MCK6 efficiently works to remove As(III) in a competitive metal ions system including Pb+2, Cd+2, and Ca+2, making it a suitable adsorbent to tackle contaminated water.