Photodegradation of Aquaculture Antibiotics Using Carbon Dots-TiO2 Nanocomposites

In this work, carbon dots (CD) were synthesized and coupled to titanium dioxide (TiO2) to improve the photodegradation of antibiotics in aquaculture effluents under solar irradiation. Oxolinic acid (OXA) and sulfadiazine (SDZ), which are widely used in aquaculture, were used as target antibiotics. To prepare nanocomposites of CD containing TiO2, two modes were used: in-situ (CD@TiO2) and ex-situ (CD/TiO2). For CD synthesis, citric acid and glycerol were used, while for TiO2 synthesis, titanium butoxide was the precursor. In ultrapure water (UW), CD@TiO2 and CD/TiO2 showed the largest photocatalytic effect for SDZ and OXA, respectively. Compared with their absence, the presence of CD@TiO2 increased the photodegradation of SDZ from 23 to 97% (after 4 h irradiation), whereas CD/TiO2 increased the OXA photodegradation from 22 to 59% (after 1 h irradiation). Meanwhile, in synthetic sea salts (SSS, 30‰, simulating marine aquaculture effluents), CD@TiO2 allowed for the reduction of SDZ’s half-life time (t1/2) from 14.5 ± 0.7 h (in absence of photocatalyst) to 0.38 ± 0.04 h. Concerning OXA in SSS, the t1/2 remained the same either in the absence of a photocatalyst or in the presence of CD/TiO2 (3.5 ± 0.3 h and 3.9 ± 0.4 h, respectively). Overall, this study provided novel perspectives on the use of eco-friendly CD-TiO2 nanocomposites for the removal of antibiotics from aquaculture effluents using solar radiation.