Degradation of antibiotic tetracycline by ultrafine-bubble ozonation process

Tetracycline (C22H24N2O8) is a well-known emerging contaminant that is generally used in pharmaceuticals and personal-care products. Traditional biological treatment technologies are inadequate for quickly and completely removing tetracycline from wastewater; hence, the ozonation investigated in this study is preferable. The effects of several reaction parameters, such as tetracycline concentration, pH, temperature, addition of ·OH radical scavengers, gas type, and bubble size, were investigated. Experimental results indicated that the connection of air or pure oxygen gas with a millibubble or ultrafine-bubble compressor could not remove tetracycline. As the ozonation was carried out, the degradation of tetracycline exceeded 99.5 %, followed by approximately 40 % mineralization with 60-min treatment. A lower pH level or a higher reaction temperature was practical to increase the degradation of tetracycline; also, the increase in the formation of ·OH radicals was impressive to mineralize further the organic compound. According to the experimental results shown in this study, ultrafine-bubble ozonation is a feasible way to degrade the antibiotics effectively and decrease the toxicity in water within a short treatment duration, and with low ozone gas consumption.