Enhanced lead and copper removal in wastewater by adsorption onto magnesium oxide homogeneously embedded hierarchical porous biochar

Removing non-biodegradable Pb2+ and Cu2+ is the top priority in wastewater purification, while adsorption is a green technology to remove them. Herein, MgO-embedded granular hierarchical porous biochar (HP-MgO@BC) was fabricated by pyrolysis of porous Mg-infused chitosan beads. MgO nanoparticles were homogeneously embedded throughout the hierarchical porous biochar matrix in a high-density and accessible manner, thus providing a large number of easily accessible adsorption sites. Pb2+ and Cu2+ sorption capacities on HP-MgO@BC are 1044.8 and 811.2 mg/g at pH 5, respectively. It could effectively remove Pb2+ and Cu2+ across a broad pH range of 2-7, and show excellent adsorption efficiency in the presence of interfering cations. It also possessed excellent reusability. In the fixed-bed operation, 7880 BV (78.80 L) and 1610 BV (16.10 L) of synthetic Pb2+ and Cu2+ wastewater could be purified by HP-MgO@BC packed column, respectively. The adsorption mechanism involves mineral precipitation, ion exchange, and surface coordination.

Automated summary

The MgO-embedded granular hierarchical porous biochar (HP-MgO@BC) fabricated in this study showed excellent adsorption capacities for Pb2+ and Cu2+ removal. It effectively removed heavy metals across a broad pH range and exhibited high adsorption efficiency in the presence of interfering cations. The HP-MgO@BC also displayed good reusability.