Removal Of Emerging Organic Pollutants Of Indometacin By Ferrate(?)

In recent years,as a kind of emerging organic micro-pollutants,pharmaceutical and personal care products?PPCPs?are causing particular concern.Indomethacin?IDM?is a kind of non-steroidal anti-inflammatory drugs?NSAIDs?which was widely used to cure analgesia and rheumatic diseases.Studies have shown that IDM is a kind of organic pollutants and it is hard to be biodegradation.Currently,the removal effect of IDM is poor by the traditional sewage treatment plant,so IDM were detected in surface water,groundwater,and even drinking water.As a kind of new,green,and multifunctional water treatment agent,ferrate?Fe?VI??showed a huge potential on the removal of PPCPs.To investigate the removal efficiency and reaction kinetics,degradation products,reaction mechanism,toxicity and the removal efficiency of target pollutant under actual water condition,we select IDM as target compound and Fe?VI?as a typical oxidizing agent to carry out our systematic study,which provide a more comprehensive evaluation of removing PPCPs by ferrate and provide theoretical and technical support for practical application in water treatment further.In this paper,the oxidation degradation of IDM by Fe?VI?was investigated.The results showed that IDM could be effectively removed in water,and the reactions were in accordance with the second-order reaction kinetics model.As the initial IDM concentration increasing from 0.010 mmol·L^-1 to 0.030 mmol·L^-1 at the concentration of Fe?VI?0.2 mmol·L^-1,the quasi-first order kinetic constants decreased from 0.1151 min^-1 to 0.0664 min^-1 and the half-life increased from 6.02 min to 10.43 min,indicating that the reactions were inhibited as the increase of IDM concentration.The reactions were also in accordance with the secondary reaction kinetics at different p H and p H had a significant effect on the reactions.The secondary reaction rate constant kapp decreased from 9.35 mol^-1·L·s^-1 to 6.52 mol^-1·L·s^-1 as p H increasing from 7.0 to 10.0 and the p H dependence of the rate constants was well analyzed with both acid-base dissociation equilibrium of IDM and Fe?VI?.The reactions were also in accordance with the secondary reaction kinetics at different temperatures too.With the increase of temperature,the reaction rates were obviously accelerated.The activation energy,enthalpy change and entropy change were 15.79 k J·mol^-1,13.27 k J·mol^-1,^-183.76 J·mol^-1·K^-1,respectively.Five oxidation products P1-P5 were detected by LC-MS/MS,speculating that IDM may undergo hydrolysis of the amide bond,hydroxyl addition and electrophilic oxidation.TOC determination experiments showed that IDM translation and mineralization were not synchronized.IDM was mostly translated while the mineralization rate was only 31.8%,indicating that most of IDM translated into intermediate products.The inhibition rate on the luminous bacteria decreased from the initial 65.3 % to 12.9%,suggesting that the reduction in toxicity may be due to the transformation of IDM and the production of lower toxic intermediates.The ECOSAR prediction model further revealed that all of the identified products P1-P5 exhibited lower acute and chronic toxicity than the parent compound for fish,daphnid,and green algae.The removal efficiency of IDM decreased under actual water condition,indicating that more oxidants were needed to achieve the target in practical application.NO₃^-,NO₂^-,Fe³⁺,Fe²⁺ and Mg²⁺ promoted the reactions,while NH⁴⁺ and HCO₃-posed almost no effect.Low concentration of fulvic acid posed little effect while high concentration significantly inhibited the reactions.