The removal of oxytetracycline (OTC) by potassium ferrate (VI) in aquatic environment

The treatment of oxytetracycline (OTC) in test solutions by ferrate (VI) was investigated aiming to propose the effects of pH, concentration of co-existing ions and humic acid on the OTC removal. Ferrate (VI) can remove 97% OTC (from 1000 µg·l^-1) in 30 minutes under the optimal conditions with solution pH of 7 and ferrate (VI) dosage of 20:1 as a molar ratio of ferrate (VI)/OTC. The effects of co-existing ions (0.005 mol·l^-1 and 0.02 mol·l^-1) and humic acid (0.1~50 mg·l^-1) on the OTC removal were investigated for the optimal operating conditions. The results showed that Ca²⁺, CO₃^2-, PO₄^3-could inhibit the OTC degradation and its removal rate decreased from 79, 29, 29% to 70, 19, 19%, for the ion concentration increased from 0.005
mol·l^-1 to 0.02 mol·l^-1. Mg²⁺ and HCO₃^- could restrain the reaction carried out at 0.02 mol·l^-1 and the removal rate was only 59%, 62%. Al³⁺could increase the removal rate which reach to 100%. Humic acid with concentrations of greater than 10 mg·l^-1 could notably inhibit the OTC removal. Regression analysis indicated good fit of the experimental date to the developed model with coefficient of determination (R²) value of 0.9991 and the adjusted R² value of 0.9978.