Enhanced solar driven photocatalytic removal of antibiotics from aquaculture effluents by TiO2/carbon quantum dot composites

Aquaculture exploitation is associated with the consumption of antibiotics, such as sulfadiazine (SDZ), sulfamethoxazole (SMX) and trimethoprim (TMP), the latter two being also vastly used to treat bacterial infections in humans. Consequently, and given that aquaculture wastewater treatments are not actually designed for the removal of antibiotics, they are ubiquitous in aquaculture effluents, which sets the risk of bacterial resistance. To face the need for an efficient and sustainable treatment to remove these antibiotics from the referred effluents, carbon quantum dots (CQDs) were produced, incorporated into titanium dioxide (TiO2), and evaluated for solar driven photodegradation of SDZ, SMX and TMP. Eleven different materials were synthesized and tested for their photocatalytic activity in phosphate buffer solution (PBS) and synthetic sea salts (SSS), used as synthetic matrices to simulate fresh and brackish water, respectively. Upon selection of the most efficient photocatalyst for each antibiotic and matrix, kinetic results demonstrated that its use allowed for remarkable reductions of SDZ, SMX and TMP half-life times (t1/2) in both matrices (between 19 and 68 times). Therefore, the application of the here synthesized photocatalysts for the advanced treatment of aquaculture effluents is promising, allowing for a green solar driven removal of antibiotics.