Study On The Degradation Of Organic Pollutants By Persulfate Activated By Iron Phthalocyanine/defective Graphene Composit

Organic pollutants are produced in many areas of people’s daily life,such as industry,medicine,agriculture,and aquaculture.They usually have complex structures and high toxicity,they will eventually merge into the aquatic environment,causing serious harm to the ecological environment and organisms.Therefore,developing effective methods to remove organic pollutants from the environment has important practical significance.Advanced oxidation process(AOP),as an advanced oxidation technology,has high efficiency in degrading and mineralizing organic pollutants into non-toxic and harmless ones,and is widely used to remove organic pollutants from water.Compared with the traditional AOP process of hydroxyl radical(·OH)as an oxidant,sulfate radicals(SO4·-)has a wider pH range(2.0-8.0)and stronger oxidation ability(half life:30-40 μs;oxidation potential:2.5-3.1 V),which can convert organic pollutants into low toxicity or non-toxic small molecule compounds,and further fully mineralize them into CO2,H2O,etc.Generally,activated peroxymonosulfate(PMS)can produce S04·-,and PMS is easy to be activated by catalyst activation,thermal activation,base activation and other ways due to its asymmetric structure.In recent years,nitrogen doped carbon materials(M-N-C)based on transition metals,such as iron(Fe),cobalt(Co),and copper(Cu)based composite catalysts,have been widely used for activating PMS due to their simple preparation process,excellent catalytic activity,and low investment cost.It is found that when the active site is in the electron rich state and bimetals exist,the active site will transfer more electrons to PMS,which is more conducive to the activation of PMS,and will also promote the regeneration of the active site.However,how to regulate the electron density of the active center of the metal site and the specific mechanism of the bimetallic synergism are still unknown.Therefore,in this paper,bisphenol A(BPA)and norfloxacin(NOR)were selected as target pollutants,and the adsorption energy between the catalyst and PMS and the ability to activate PMS were improved by regulating the electron density of Fe-N4 active site and doping the second metal.The main research content is as follows:1.FePc/DG composite enhances peroxymonosulfate activation for bisphenol A degradation and mechanism.Heterogeneous FePc/DG composite was prepared by utilizing the π-π and coupling interactions between FePc molecules and defective graphene substrates(DG).DG as a support can not only improve the dispersity of FePc and avoid aggregation,but also the defect sites of graphene can transfer electrons to the Fe site in FeN4 active site,making it in an electron rich environment.Density functional theory(DFT)shows that the Fe-N4 site in an electron rich environment has the maximum adsorption energy with PMS,which can transfer more electrons to PMS(0.77 e),promoting the cleavage of O-O bonds in PMS and producing active substances to degrade BPA.The FePc/DG-PMS system can effectively degrade BPA(with a removal rate of 100%within 10 min),has excellent resistance to background interference(pH,anions,and water quality),and has excellent removal efficiency for other typical pollutants.It also has excellent cycling stability(with a degradation rate of 100%after five cycles).2.FeCuPc/DG composite enhances peroxymonosulfate activation for norfloxacin degradation and mechanism.The above experiments indicate that the FePc/DG composite cannot completely remove NOR in a short period of time,previous studies have shown that the addition of Cu sites can promote the effective reduction of Fe(Ⅱ),forming a cycling system of Fe(Ⅱ)/Fe(Ⅲ)and Cu(Ⅰ)/Cu(Ⅱ),ensuring the efficient catalytic activity of the catalyst.Based on the synergistic effect between bimetallic iron and copper,a heterogeneous FeCuPc/DG composite catalyst was successfully prepared through the π-πand coupling interactions between FePc and copper phthalocyanine(CuPc)molecules and DG,and was used to activate PMS for the degradation of NOR.Compared with the above FePc/DG composite for activating PMS to degrade NOR(with a removal rate of 95.7%within 60 min),the FeCuPc/DG composite can achieve 100%removal of NOR within 20 min.The addition of trace Cu sites promoted the cycle of Fe(Ⅲ)/Fe(Ⅱ)and the regeneration of active site.The activation of FeCuPc/DG composite for PMS degradation of NOR shows excellent practical applicability,and can also achieve 100%removal of NOR in 20 min for background disturbances(pH,anions,and water quality).The removal rate of other typical pollutants also reaches 100%,while demonstrating good cycling stability.In this paper,we use the method of manufacturing defects and the synergistic effect of Fe and Cu to modify the metal active site,deeply study the efficiency and mechanism of catalyst activated PMS to degrade organic pollutants,and provide new insights into the heterogeneous AOP based on persulfate.