Pharmaceutical residues, particularly from antibiotics, are extremely difficult to fully remove from wastewater using traditional bulk-treatment methods, wherein antibiotic compounds are often only partially broken down. Even at trace amounts, antibiotic fragments can accumulate and wreak havoc on natural ecosystems. A significant source of antibiotic water pollution is livestock farming. Photocatalytic degradation with titanium dioxide (TiO2) and adsorption using carbonaceous materials like biochar have both been posited as potential treatment solutions for antibiotic contamination in effluent water, but both have their drawbacks. Photocatalytic treatment, while effective at fragmenting complex molecules into smaller, more benign compounds, is limited by its efficiency and scale. And while quite cost-effective for preliminary water treatment, adsorption-based methods are hampered by the complex conditions posed in real-world effluent streams.
Researchers from the National Taiwan University (Taipei; www.ntu.edu.tw) have now developed a new nanocomposite comprising graphene oxide, biochar and TiO2 (GBT) that bridges the strengths of photocatalytic and adsorption-based treatment techniques.
For both the adsorption and photocatalytic function, the integration of graphene oxide plays a key role. Its combination with biochar has been shown to enhance surface reactivity and overall adsorptive capacity via its diverse binding sites and oxygenated groups. Graphene oxide’s presence also enhances electron conductivity, which helps to overcome some of the scale limitations of photocatalysis using TiO2 alone.
Ultimately, the GBT nanocomposite enables a level of synergy that traditional bulk-treatment methods cannot achieve. Antibiotics are first adsorbed and concentrated onto the graphene-oxide-biochar matrix, and then photocatalytically degraded using light-activated TiO 2. Over five cycles treating actual antibiotic-laden effluent streams from livestock farming, the researchers reported that the optimized GBT nanocomposite maintained greater than 90% efficiency and 92% stability of the TiO2 phase during “adsorption-enhanced photocatalysis.”
The results of this study were originally published in the October 2025 issue of Chemical Engineering Journal.