# name
Valorisation of viticultural residues into CO2-activated biochar for micropollutant removal from water

# metadata.dc.description[].value
Treballs Finals de Grau de Química, Facultat de Química, Universitat de Barcelona, Any: 2026, Tutors: Pere Llopart Roca, Bernardí Bayarri Ferrer

# metadata.dc.description.abstract[].value
The continuous release of trace organic micropollutants (MPs) into aquatic environments represents a major challenge for wastewater treatment, since conventional wastewater treatment plants (WWTPs) are not specifically designed to completely remove persistent contaminants. In response to Directive (EU) 2024/3019, which establishes advanced quaternary treatment requirements for MP removal from urban wastewater, this work evaluates adsorption using biomass-derived activated biochar (AB) as a sustainable and circular alternative to commercial activated carbon. Specifically, three viticultural residues, grape stalks (GS), vine pruning residues (VPR) and grape pomace (GP), were valorised as precursors for CO2-activated biochar aimed at removing two representative indicator MPs from the Directive: venlafaxine (VEN), a Category 1 pharmaceutical compound, and 4-methylbenzotriazole (4BEN), a Category 2 corrosion inhibitor.
The ABs were synthesized through sequential N2 pyrolysis and CO2 physical activation at 800 ºC using different activation times. The optimal materials were subsequently subjected to acid washing (AW) to remove pore-blocking inorganic ashes and increase pore accessibility. Feedstocks and ABs were characterized by TGA, elemental analysis, ash content, particle-size analysis, BET, SEM-EDS, FTIR, Raman spectroscopy and XPS. Their adsorption performance was evaluated through preliminary screening, equilibrium isotherms and kinetic experiments, and the experimental data were analysed by non-linear Langmuir, Freundlich, pseudo-first order (PFO), pseudo-second order (PSO) and Elovich models.
The results demonstrated a strong precursor-dependent activation behaviour. GS developed adsorption-accessible porosity rapidly, reaching its optimal performance at 80 min, whereas VPR required 120 min to achieve the best balance between pore development and structural preservation. GP showed a slower and less efficient activation response, mainly attributed to restricted CO2 diffusion, compact bed formation and poorer development of an accessible microporous network. Pyrolysis alone was insufficient for efficient MP removal, while excessive CO2 activation caused overactivation, pore widening, carbon burn-off and loss of adsorption capacity. AW proved essential, reducing ash content to 0.84% for GS-80′-AW, 0.67% for VPR-120′-AW and 1.71% for GP-120′-AW, while increasing the specific surface area up to 1303.9 m2 g-1 for GS-80′-AW and 1286.6 m2 g-1 for VPR-120′-AW, both above the commercial F 400 reference.
The optimized GS- and VPR-derived ABs outperformed Chemviron FILTRASORB 400 in equilibrium adsorption. According to the Langmuir model, GS-80′-AW reached maximum capacities of 254.78 mg g-1 for VEN and 338.55 mg g-1 for 4BEN, while VPR-120′-AW reached 293.78 mg g-1 for VEN and 270.24 mg g-1 for 4BEN. Adsorption was governed by a mixed mechanism involving micropore filling, π-π electron donor-acceptor interactions, hydrophobic effects and, for cationic VEN at pH 7, electrostatic attraction. The Freundlich model described 4BEN adsorption well on the AW ABs, indicating heterogeneous active sites, whereas VEN showed a more precursor-dependent behaviour. Kinetically, 4BEN was adsorbed faster due to its smaller, planar and neutral structure, while VEN uptake was more limited by molecular size, steric hindrance and intraparticle diffusion. Overall, this work validates GS and VPR as promising local precursors for producing high-performance, zero-kilometre ABs for circular quaternary wastewater treatment.

# metadata.dc.rights[].value
cc-by-nc-nd (c) Bombardó Heras, Marc, 2026

# metadata.dc.title[].value
Valorisation of viticultural residues into CO2-activated biochar for micropollutant removal from water