Entrapment of laccase-halloysite nanotubes in chitosan beads for pharmaceutical degradation in wastewater

The presence of pharmaceuticals in water has emerged as a significant environmental concern. This study investigated the degradation of sulfamethoxazole (SMX), tetracycline (TC) and acetaminophen (APAP) using laccase from Lentinus sajor-caju immobilized by adsorption on halloysite nanotubes (HNT) and subsequent entrapment in chitosan (CS) beads. The immobilization process was successfully confirmed through Transmission Electron Microscopy and Fourier Transform Infrared Spectroscopy, achieving high immobilization yield (89 %) and protein loading (79 %) using 15 U mL −1 of enzyme and 75 mg of HNTs. Stability studies demonstrated that immobilized laccase exhibited superior performance compared to the free enzyme under various conditions, including pH, temperature, long-term storage and reusability. Furthermore, the immobilized laccase was successfully applied to degrade emerging pollutants using a natural phenolic mediator, syringaldehyde. Complete removal of SMX and TC was achieved in 30 min and 2 h, respectively, using the laccase–mediator system. For APAP, 82 % removal was reached after 24 h with laccase. Ultra-high liquid chromatography with mass spectrometry was employed to elucidate the degradation pathways, revealing key oxidative and coupling reactions involved. Moreover, CS-HNT-laccase was successfully applied for pharmaceutical degradation in municipal wastewater. This work presents novel and high-performance material for environmental remediation, offering a robust and reusable solution for micropollutant degradation. • Laccase was immobilized via adsorption on HNTs and entrapment in chitosan beads. • Immobilized laccase retained >80 % activity after 30 days at 4 °C storage. • 82 % APAP was degraded with laccase, and 100 % SMX and TC by adding the mediator. • Degradation mechanisms involved oxidative and coupling reactions. • The system showed complete SMX removal in municipal wastewater after 2 h.