Research On Metal Phthalocyanine-sensitized Organic/inorganic Hybrid Photocatalyst

With the continuous progress of mankind and the continuous development of industry,the discharge of waste water,waste gas and other pollutants had been increasing,which resulted in increasing environmental pollution,posing a huge threat to the ecological environment and human health.The pollutants mainly include organic pollutants,heavy metal ions,and solid refractory wastes.Therefore,it was extremely important to find a suitable pollutant treatment technology.As a green and natural pollutant treatment technology,photocatalysis technology could quickly oxidize organic matter and reduce heavy metals into harmless small molecules or less toxic substances,which opened up a new idea for solving environmental and energy problems,showing a good application prospects.The key to photocatalytic technology was the preparation of efficient photocatalysts.Traditional semiconductor photocatalysts had attracted much attention due to their good photoelectrochemical properties,high chemical stability,harmless to human body and mature preparation process.However,due to the wide band gap,the low utilization of visible light,high recombination rate of photogenerated electron-hole pairs and easy agglomeration still limited their further development of semiconductor materials in the field of photocatalysis.Metal phthalocyanines,due to their narrow band gap and good response to visible light,had shown great application in the field of visible light catalysis.Therefore,it is of great significance to design and synthesize efficient photocatalysts,especially in the response of visible light.This paper combined metal phthalocyanines with different inorganic materials（Ti O₂,Cu₂O and Zn In₂S₄）to construct a new organic/inorganic hybrid photocatalytic system with recovery characteristics.The photocatalytic degradation of organic pollutants and the reduction of hexavalent chromium Cr（VI）were investigated under visible light.The main research contents and related conclusions are as follows:1.ZnPc-g-Ti O₂-g-PNIPAM photocatalysts with temperature sensitivity and visible light response was prepared,which could be recovered by temperature without secondary pollution.Firstly,Ti O₂ was modified with 3-（methacryloxypropyl）-trimethoxysilane and then poly（N-isopropylacrylamide）（PNIPAM）was introduced on the surface of photocatalysts by radical polymerization to obtain Ti O₂-g-PNIPAM.Then Zn Pc-g-Ti O₂-g-PNIPAM was obtained by the interaction between zinc-tetra（N-carbonylacrylic）aminephthalocyanine（Zn Pc）and-OH on the surface of Ti O₂-g-PNIPAM.The lower critical solution temperature（LCST）of Zn Pc-g-Ti O₂-g-PNIPAM was 26°C,when the temperature was above 26°C,photocatalysts could be separated from aqueous solution.Photocatalysts had strong absorption in the visible light range,the degradation of rhodamine B（Rh B）and methylene blue（MB）in 40min were 97.2%and 88.6%at 20°C,respectively.At the same time,the photocatalytic performance of Zn Pc-g-Ti O₂-g-PNIPAM would be influenced by temperature.When the temperature was 45°C,the degradation rate of Rh B was only 43.4%.The good photocatalytic and recovery ability due to two aspects:one was that Zn Pc sensitized Ti O₂ to broaden the light absoption to visible light and promote the transfer of photogenerated electrons;the other was the introduction of PNIPAM,which gave the photocatalyst temperature sensitivity.2.Magnetic and thermal responsing Zn Tc Pc-g-Fe₃O₄@Si O₂@Ti O₂-g-PNIPAM photocatalyst was prepared.The Fe₃O₄ was prepared by solvothermal method and then coated with Si O₂ and Ti O₂ to obtain Fe₃O₄@Si O₂@Ti O₂.After modification with3-（methacryloxypropyl）-trimethoxysilane,PNIPAM grafted on the surface of photocatslysts by radical polymerization and zinc-tetracarboxyl-phthalocyanine（Zn Tc Pc）immobilized on it by chemical bond.The LCST of Zn Tc Pc-g-Fe₃O₄@Si O₂@Ti O₂-g-PNIPAM was 30°C,when the temperature was below 30°C,the particle distribution was uniform and photocatalysts could disperse stably,when the temperature was above 30°C,particles tended to aggregate and could be separated from aqueous solution with the applied magnetic field.The degradation rates of Rh B and MB by Zn Tc Pc-g-FST-g-PNIPAM（0.2g/L）under visible light were 91.8%and 98.8%at 25°C in 60 min.When the temperature was 45°C,the degradation rate of Rh B was only 37.0%.After four cycles,the degradation rate of Rh B was still up to more than 80%.The further study showed that Zn Tc Pc-sensitized Ti O₂ improved the separation efficiency of electron-hole pairs and showed a good response to visible light;secondly,the inner magnetic Fe₃O₄ and outer thermosensitive PNIPAM improved the recyclability of photocatalysts.3.A hollow-structured organic/inorganic hybrid Cu₂O@Ti O₂-g-Zn TAPc composite photocatalyst based on double modification of Cu₂O and zinc-tetraamino-phthalocyanine（Zn TAPc）was successfully prepared.The photocatalyst had photocatalytic activity in dark and could be used to treat pollutants day and night.Si O₂ used as template.Then,Cu₂O and Ti O₂ were sequentially coated on Si O₂.The outer surface of materials was modified with maleic anhydride to graft Zn TAPc by chemical bond.Finally the hollow structure of photocatalysts was obtained by Na OH etching.The specific surface area of the photocatalyst was 219.3m²/g.The maximum adsorption capacity for Cr（VI）was 48.8mg/g by the Langmuir model.The reduction rate of Cr（VI）by Cu₂O@Ti O₂-g-Zn TAPc（0.5 g/L）was 95.2%in 200 min,and the degradation rate of tetracycline hydrochloride（TC·HCl）was 87.1%in 100 min under visible light.In the coexistence system of Rh B and Cr（VI）,the removal rate for Rh B was 96.8%and for Cr（VI）was 83%in 200 min.Meanwhile,the reduction rate of Cr（VI）by Cu₂O@Ti O₂-g-Zn TAPc（0.5 g/L）was 73.9%under dark conditions after pretreatment with visible light in 2 h.The significant improvement in the performance of the photocatalyst was attributed to the synergistic sensitization of Cu₂O and Zn TAPc on Ti O₂,which improved the response of photocatalysts to visible light and reduced the recombination rate of photogenerated electron-hole pairs.4.Fe₃O₄@Si O₂@Ti O₂@Zn In₂S₄/Zn Pc photocatalyst with dual mechanism response of recovery was prepared.The photocatalyst was supported by Fe₃O₄@Si O₂@Ti O₂ and then modified by Zn In₂S₄ and Zn Pc.The specific surface area of FSTZP was 82.5m²/g.The maximum adsorption capacity for Cr（VI）was 132.28mg/g by the Langmuir model.The reduction rate of Cr（VI）by FSTZP（0.3 g/L）under visible light was 96.4%in 60 min,and the removal rates of Rh B,MB,methyl orange（MO）and TC·HCl were 99%,99%,95%and86%in 40 min,respectively.It was also suitable for removing the pollutants coexistence systems.And photocatalysts could be separated by magnetic technology and exhibited good recycle stability.Further analysis proved that the excellent performance of the photocatalyst could be attributed to the following three factors:Zn In₂S₄-modified could provide more active sites and promote the separation of photogenerated electron-hole pairs;Zn Pc provided a full use of visible light;photocatalysts could be quickly separated under external magnetic field.