Production and application of carbon-based biomaterials in the adsorption of Critical Raw Materials (CRMs) from solutions

The use of biomass-derived biochar has gained attention due to its environmental benefits and versatility. Initially applied in soils for carbon sequestration and improved fertility, biochar is now also being explored for wastewater treatment. Biochar and its modified forms have shown high efficiency in removing heavy metals from solution, offering advantages such as low cost, sustainability, and effective contaminant sorption at low concentrations. This thesis presents the development of novel magnetic biochars using potabilization sludge and pruning waste, applying an industrial symbiosis approach. This innovative material has been patented through the University of Bologna. The magnetic biochars and other biochar-based materials were applied for the removal of Critical Raw Materials (CRMs) from solution. Specifically, arsenic, boron, and manganese were selected as target contaminants. A dolomite-biochar composite showed promising results, with arsenic adsorption of 3 mg g⁻¹ and boron reduction below the regulatory limit of 2 mg L⁻¹ for surface waters. Manganese adsorption was evaluated using pristine biochars in both synthetic and mine-impacted waters, showing good performances on both matrices. Overall, this research demonstrates that magnetic and modified biochars are viable, sustainable materials for wastewater treatment and resource recovery. They offer a circular economy solution by valorizing waste while addressing contamination. Further studies should focus on enhancing sorption in complex matrices, scaling up production, and investigating the recovery and reuse of spent biochars.