Photocatalytic vs. sonochemical removal of antibiotics in water: Structure-degradability relationship, mineralization, antimicrobial activity, and matrix effects

Abstract

Intrinsic abilities of heterogeneous photocatalysis (PC) using TiO2-P25 and high-frequency ultrasound (US) to degrade penicillins, cephalosporins, quinolones, and sulfonamides in water were compared. The degradation efficiency and elimination order in distilled water were associated with the chemical structures and properties of antibiotics. After 60 min of treatment by PC and 30 min of treatment by US, similar trends were obtained for penicillins (PC: oxacillin (93%) > ampicillin (75%); US: oxacillin (83%) > ampicillin (76%)) and cephalosporins (PC: cephradine (91%) > cephadroxil (58%); US: cephradine (70%) > cephadroxil (30%)); whereas inverse trends were obtained for quinolones (PC: ciprofloxacin (91%) > nalidixic acid (86%); US: nalidixic acid (86%) > ciprofloxacin (54%)) and sulfonamides (PC: sulfacetamide (72%) > sulfamethoxazole (56%); US: sulfamethoxazole (66%) > sulfacetamide (47%)). PC showed a great mineralizing potential (TOC removal: 65% for oxacillin, and 55% for cephadroxil in 4 h), whereas US had a higher capacity to decrease antimicrobial activity (100% of removal). Furthermore, individual degradation of indicative antibiotics in simulated fresh urine and mineral water, plus the effect of basic pH were considered. The fresh urine inhibited antibiotics degradation in both processes (∼23% in PC, and 10% in US). The removal of antibiotics in mineral water was enhanced in US (∼12%) and slightly inhibited in PC (∼5%). The basic pH inhibited the antibiotics degradation by PC (∼10% for oxacillin, and ∼5% for cephadroxil), whereas US was no affected. This work provides valuable insights to contrast PC and US for selecting the suitable technique to remove antibiotics from water.