| There is a large number of reports about the detection of Pharmaceuticals and personal care products?PPCPs?in various water bodies,which gradually arouse widespread concern in the past several decades.Antidepressant is an important branch of PPCPs,which accumulates and persists in the water environment,and the traditional water treatment method cannot effectively remove it.Materials like the ferric ions?Fe????,oxalate?ox?,citrate?cit?are widely spread in the natural waters forming Fe???-carboxylate complexes,which can degrade PPCPs effectively under solar light.In this study,Amitriptyline?AMT?,a tipical tricyclic antidepressant,is chosen to be the research object,to discuss thedegradation kinetics and mechanism of AMT under Fe???-cit-ox complexes for the first time.And analyze the synergistic effect of Fe???-bicarboxylic system and the effectsof different water conditionson the photodegradation as well.By discussing the degradation of AMT under the condition of different pH and Fe???/carboxylate ratio of the two kinds of single carboxylate system,compare them with the photodegradation of Fe???-cit-ox system of bicarboxylate system,and a discussion is made about the synergistic effect of bicarboxylate,the results are as follows:?1?The photodegradation of AMT in the Fe???-ox system,Fe???-cit system,Fe???-cit-ox system all accord with First order kinetic reaction.The effect is related to the concentration of carboxylate and the pH.The higher the carboxylate concentration,the greater the rate constant of the AMT photodegradation,When the pH value is 3.0-8.0,the lower the pH,the greater the rate constant in Fe???-ox system and Fe???-cit-ox system while in Fe???-cit system,the photodegradation efficiency from high to low pH value is5.0>3.0>6.0>7.0>8.0.?2?Compared with Fe???-ox system,Fe???-cit system has a better efficiency at circumneutral pH when the ratio of Fe???to carboxylate change from10:50 to 10:500.When pH<5.0 at the same ratio,degrading rate of Fe???-ox system is much faster.?3?Compared with the single carboxylate systems,Fe???-ox-cit system has a better efficiency when degrading AMT.And the existence of cit increases the optimum pH range while the existence of ox enhances the efficiency of photodegradation.So ox and cit have synergistic effect under certain conditions:pH=3.0 without synergistic effect,when pH range from 5.0 to 8.0,there is synergistic effect when the carboxylate concentration is relatively high.When pH=6.0,the synergistic effect and degradation effect are both good.?4?Halide ions inhabit the photodegradation of AMT in Fe???-cit-ox system.And the inhibition increasing order is:Cl-<Br-<I-.Three other anions,SO42-,NO3-and PO43-,have no obvious effect while CO32-inhibits it.Cations like Na+and K+have no impact while Ca2+,Mg2+decrease the photodegratadion rate.In addition,the degree of inhabitation of the two cations is quite close.Humic substances also inhibit the reaction,and the fucntion of HA is more obvious than FA.?5?Natural waters inhabit the photodegradation,strong to weak inhabitation in order:Yangtze River water>East Lake water>Liangzi Waters>Deionized water.The degree of inhibition is related to the concentration of some ions in the water and water quality.?6?Through the detection of LC-MS products,the intermediate products of the photodegradation of AMT in Fe???-cit-ox complexes were analyzed,and the possible pathway was speculated.The hydroxyl·OH oxide aromatic rings,after further hydrolysis and oxidation,AMT is oxidized to 3-dimethylamino-propionaldehyde and dibenzosuberone?C15H12O?.Photodegradation kinetics and mechanism of AMT under Fe???-cit-ox system are investigated in this paper for the first time,and it is concluded that Fe???-cit-ox system has synergistic effect on photodegradation of AMT at near-circumneutral pH condition.The investigation of effect on humic substances,some ions in various water bodies and some actual water bodies has a certain reference value to the applyment to use this system in the natural water. |
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