Control Of The Combined Pollution Of Antibiotics And Heavy Metals In Aqueous Solution By Ferrate

It was widely reported that antibiotics and heavy metal ions could coexist in the aquatic environment.Antibiotics have strong tendency to chelate with heavy metal ions,which would exercise considerable influence over their physicochemical property,transformation,and eco-toxicity.It gives rise to great challenge for the water treatment process.Ferrate（VI）has strong oxidation ability to organic pollutants.Moreover,the reduced ferrate（VI）into ferric（Ⅲ）may act as coagulant to remove heavy metals ions.In this study,the effect of potassium ferrate on the control of the tetracycline（TC）and copper ion(Cu²⁺)combined pollution was investigated.The removal mechanism was analyzed after combining experiments and theoretical calculations.In order to further improve the efficiency of potassium ferrate in simultaneously removing TC and Cu²⁺,the oxidation technology of ferrate had been strengthened.In the sole pollution system,potassium ferrate（50μM）had a high removal efficiency of TC（10μM）and Cu²⁺（10μM）,but a low removal efficiency of Cd²⁺（10μM）.In the combined pollution system,only 79.7%of TC and 19.3%of Cu²⁺were removed,which were lower than that of the sole pollution system.The reaction mainly occurred in the first 1 minute.Parameters which had certain effects on the removal efficiency of pollutants such as the concentration of ferrate,TC and Cu²⁺,p H and temperature were explored.The LC-MS and DFT calculations implied that the main removal mechanism of TC were oxidation and adsorption.Cu²⁺decreased the sorption of TC as a result of electrostatic repulsion.Cu²⁺suppressed the oxidation of TC due to the complexation.It was confirmed by the theoretical analysis that the complexation occurred at O atoms of C11 and C12,or O atom of C3 and N atom of C4 to form stable ring-type moiety.The inhibition effect of Cu²⁺was explained by electrostatic potential and the highest occupied molecular orbital that the negative charge and HOMO energy of TC were decreased.The theoretical analysis result was consistent with that obtained from the product analysis and thus suggested that participation of Cu²⁺could alter the regioselectivity of the reaction.The XPS implied that the complexation of TC and Cu²⁺inhibited both the precipitation and adsorption of Cu²⁺.Ferrate combined with Mn²⁺,biochar,activated carbon,Fe³⁺and PAC improved the removal effect of Cu²⁺.After pre-oxidation by ferrate for 1 minute,adsorption by activated carbon or flocculation by PAC for 20 minutes,and precipitation for 20 minutes in order,the removal of TC and Cu²⁺were both significantly promoted.