Comparison of UV-C irradiation, ozonation, and iron chelates treatments for degradation of tetracycline in water

The objective of this study was to propose a method for efficient degradation of tetracycline as a water contaminant. UV-C rays, ozonation, and iron chelates were used for removal of tetracycline from water. Aqueous solution of tetracycline (5 × 10−5 M) was exposed to UV-C rays (in two doses—6 and 12 W), ozonation (at 6–12 mg ozone), or iron chelates: iron(III) sodium ethylenediaminetetraacetate, iron(III) trisglycinate, and iron(III) citrate. For each of iron compounds, three doses were studied: 2.5 × 10−5 M, 5 × 10−5 M, 10 × 10−5 M. The experiments have shown that aqueous solution of tetracycline (5 × 10−5 M) is immediately degraded as a result of ozonation with 12 mg ozone. Absorbance of tetracycline decreased from A = 0.78 to A = 0.35 after 20-min ozone treatment of sample. The fluorescence spectra revealed the presence of two ozone-induced TC degradation products with fluorescence maxima at 523 and 531 nm appearing immediately after the ozonation treatment. On the other hand, iron(III) sodium ethylenediaminetetraacetate and iron(III) trisglycinate gave rise to a single TC degradation product with a fluorescence maximum at 531 nm, observed after 10 days of the experiment. On application of iron(III) trisglycinate, at any studied concentration, tetracycline becomes degraded faster—in 4 days. Iron(III) citrate degraded 90 % of tetracycline, when used at the level 10 × 10−5 M. The biggest changes in tetracycline concentration were obtained as a result of ozonation and iron(III) citrate treatments.