The degradation of oxytetracycline with ferrous oxalate under different light irradiation

Degradation of OTC under different light with Fe²⁺/$$ was investigated, and the reaction mechanism was also discussed. Although Fe(II/III)-$$ complex could weaken the inhibitory effect of Fe(II/III)-OTC complex on the detection of OTC by HPLC, the acidification could make inhibition become minimal. Response surface methodology was used to optimize the Fe²⁺/$$ dosage at low concentrations of Fe²⁺ and H₂C₂O₄. When the OTC concentration was 0.04 mM, the optimal dosage was OTC:Fe²⁺:H₂C₂O₄= 1:1.25:2 to attain a removal rate of 80% after 60 min under simulated solar light, and HO^• for degradation of OTC with Fe²⁺/$$ could be 53%, furthermore, removal rate of OTC just increased 3 percentage points at 60 min when the simulated solar light changed into UV-254 nm, however, OTC could also be degraded for 48.89% removal rate after 3 h illumination of simulated visible light. The influence of Cl^-, $$, $$, $$, $$, or $$ on the degradation of OTC with Fe²⁺/$$ under simulated solar light was studied. $$ could inhibit degradation for $$ could react with free radicals, but the reason of inhibition of degradation by $$, or $$ was its influence on pH, whereas Cl^-, $$ and $$ had no influence on degradation. In addition, when the concentration of $$ was higher than 4 mM, $$ could promote the degradation for the direct photolysis of OTC at alkaline (pH > 10). Four products were detected by LC-MS, and the OTC degradation pathway was discussed.