Selenite adsorption using leached residues generated by reduction roasting-ammonia leaching of manganese nodules

► Leached residue generated by reduction roast-NH3 leaching of manganese nodules was used. ► Se loading on untreated leached residue was 6.91 mg Se/g. ► Heat-treatment improved Se loading capacity. ► Achieved the goal of successful residue utilization for selenite removal.