Facile fabrication of highly porous MgO-modified biochar derived from agricultural residue for efficient Cd(II) removal from wastewater

MgO-modified biochar (MgO-BC) has demonstrated enormous potential for practical application of Cd(Ⅱ) removal from wastewater. Exceptionally numerous MgO adsorption sites and enhanced porosity of MgO-BC are both critical for efficiency Cd(Ⅱ) removal. However, the pursuit of high-content of MgO while maintaining unobstructed pore structure remains a challenge due to the blockage of BC pores by the MgO particles. Herein, we demonstrated that Mg(NO 3 ) 2 can synergistically enhance the porosity and MgO active site of biochar attributing to the oxidation of nitrate. The prepared MgO-BC exhibits highly porous framework structure. Remarkably, further adsorption results indicate the MgO-BC has outstanding adsorption capacity of Cd(Ⅱ) in solution. The immobilized contaminant Cd(Ⅱ) onto MgO-BC was predominantly attributable to the chemical and physical interaction, including ion exchange, cation-π interaction, surface complexation and electrostatic interaction. This strategy demonstrates a novel route to develop efficient adsorbents by tailoring structure and metal oxide via nitrate activation.