The persistent release of antibiotic compounds into rivers, lakes, and wastewater systems is a global environmental emergency, increasing the threat of antibiotic resistance. Conventional water treatment often fails to completely eliminate these molecular pollutants. However, a comprehensive review in the journal Materials Advances by Van Doan Nguyen, The Anh Luu, Guo-Ping Chang-Chien, and Van Giang Le spotlights how biochar is being engineered into a high-performance solution for antibiotic removal.

The core finding is a dramatic increase in pollutant uptake achieved through strategic material modification. While traditional biochar from materials like sewage sludge and wood offers low-to-medium adsorption capacities, typically ranging from 7.91 to 120 mg/g, advanced modification techniques showcase unparalleled efficiency. For example, N, S co-doped biochar achieved an outstanding 1480.10 mg/g for tetracycline (TC) removal, representing an approximate 17.5-fold improvement over top-tier traditional biochars. Even N-doped graphitic biochar reached 1377.83 mg/g for sulfamethoxazole (SMX) and 1070.40 mg/g for ciprofloxacin (CIP). This demonstrates that the integration of heteroatoms and a graphitic structure is key to next-generation adsorbents.

To transform low-cost biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More waste into potent adsorbents, researchers employ several cutting-edge strategies. Simple thermal activation, like steam activation of sewage sludge biochar, achieved a remarkable surface area of 1583.07 m2/g and an SMX adsorption capacity of 204.07 mg/g in 90 minutes. Mechanical treatment using ball milling can increase corn stover biochar’s surface area up to 194 m2/g, 60 times larger than the original material, by fracturing chemical linkages and exposing the carbon’s surface.

More complex chemical modifications, particularly atomic doping, are responsible for the highest efficiencies. Dopants like Boron (B), Nitrogen (N), and Phosphorus (P) introduce highly active functional groups and alter the material’s electronic structure. B-doped biochar, for instance, achieved a TC uptake capacity of up to 413.22 mg/g, largely due to π−π electron donor-acceptor (π−π EDA) interactions facilitated by the -BCO2​ functional group.

The review also highlights hybrid biochar architectures, combining biochar with advanced nanomaterials like Metal-Organic Frameworks (MOFs) and MXenes. Lignin-doped Biochar/MIL-101-NH2​(Fe) exhibited exceptional TC adsorption performance with a maximum uptake of 760.36 mg/g. The combination is powerful because biochar is low-cost, MOFs offer huge surface areas and tunable porosityPorosity of biochar is a key factor in its effectiveness as a soil amendment and its ability to retain water and nutrients. Biochar’s porosity is influenced by feedstock type and pyrolysis temperature, and it plays a crucial role in microbial activity and overall soil health. Biochar More, and MXenes provide superior conductivity and active surface groups.

A significant shift in the field is the growing reliance on quantum computational tools, specifically Density Functional Theory (DFT), to move beyond empirical observation and clarify adsorption mechanisms at the atomic level. DFT simulations confirm that adsorption often proceeds via chemisorption, a stable process involving strong intermolecular forces. Key interactions identified include-

• π−π EDA Interactions: DFT unequivocally demonstrated that the efficiency and stability of adsorption are directly proportional to the number of aromatic rings in the antibiotic molecule and the graphitization degree of the biochar. For sulfamethazine (SMT), the most stable bonding configuration involves a parallel orientation between the aromatic ring and the biochar’s graphene surface.
• Role of Functional Groups and pH: Calculations revealed that oxygen-containing groups, particularly -COO− (carboxylate), are the strongest adsorption sites, with uptake energy reaching −0.600 eV in alkaline conditions. This is because pH alters the ionization state of both the antibiotic and the biochar surface, dramatically modifying the electronic interaction capacities.
• Metal Ion Bridging: DFT studies on multi-pollutant systems showed that metal ions like Cu2+ and Zn2+ do not just compete; they often enhance adsorption by forming a stable five- or six-membered chelate ring that bridges the biochar’s carboxyl group and the antibiotic’s functional groups. This bridging mechanism resulted in adsorption energies exceeding the threshold for physical adsorption.

Source : Nguyen, V. D., Luu, T. A., Chang-Chien, G.-P., & Le, V. G. (2025). Progress in Biochar Derived Adsorbents: Preparation, Modification Strategies, and Applications for Remediation of Antibiotics from Wastewater. Materials Advances. Advance Article.