Lavender-Derived ZnO/Biochar for Photocatalytic Degradation of Doxycycline and Paracetamol

The increasing release of pharmaceutical pollutants, particularly antibiotics and analgesics, into aquatic environments poses a significant environmental challenge and necessitates sustainable removal strategies. In this study, lavender-derived biochar was produced by pyrolysis at 450 and 650 °C and subsequently modified with Zn2+ (3 and 5 mmol) via a solvothermal method. The resulting materials were evaluated as photocatalysts for the degradation of doxycycline and paracetamol in distilled water under UV-A irradiation. Structural and optical characterization (SEM–EDS, XRD, PL, FTIR) was conducted to elucidate structure–performance relationships relevant to photocatalytic activity. The sample pyrolyzed at 450 °C and modified with 5 mmol Zn2+ exhibited the highest photocatalytic performance, achieving degradation efficiencies of 62.78% for doxycycline (k = 0.0032 min−1) and 75.19% for paracetamol (k = 0.0113 min−1). The results demonstrate that controlled Zn incorporation into lavender-derived biochar enhances photocatalytic performance and highlight the role of synthesis parameters in governing catalytic behavior. This work underscores the potential of agro-waste-derived biochar as a functional matrix in sustainable photocatalytic systems.