Preparation Of Poly(Ionic Liquid)/Cobalt Phthalocyanine Complexes And Their Photocatalytic Activity

Today,the shortage of water resources and the pollution of water environment have caused increasing attention.Especially the industrial wastewater from the printing and dyeing industry has become one of the main sources of pollution.Due to the complicated composition,stable property,difficult decomposition and high toxicity of dyes,dye wastewater is difficult to treat only by simple physical and chemical methods.So,developing an effective method for treating dye pollution sources has great development prospects and practical significance.Photocatalytic oxidation is commonly applied to the degradation of organic pollutants.Metal oxides,metal ions or metal complexes capable of generating hydroxyl radicals?·OH?with extremely high oxidation potential?2.8 eV?are mostly used as photocatalysts.Due to their excellent semiconductor properties and photoelectric properties,metal phthalocyanines are widely used in photocatalytic oxidation field.The greatest advantage of such compounds is that the reactions catalyzed by them can be carried out under low temperature conditions with faster catalytic rate and the better effect.However,metal phthalocyanines tend to aggregate to form dimers or polymers and are hardly soluble in water and various organic solvents due to strong?-?interaction between molecules,which largely limits the development of metal phthalocyanines in the field of photocatalysis.In order to solve the problem of aggregation of metal phthalocyanines,the metal phthalocyanines or their derivatives are mostly supported on different supports?such as TiO₂,graphene,etc.?.However,the catalysts preparation steps are complicated and the raw material costs are high,which limit their practical application.In this paper,a simple coprecipitation method is used to prepare a poly?ionic liquid?/tetracarboxyl cobalt phthalocyanine complexes by using the electrostatic interaction between the negative charge of tetracarboxyl cobalt phthalocyanine and the positive charge of poly?ionic liquid?cation in alkaline solvents.The catalytic activity of the complexes was evaluated by using the dye Rhodamine B as the target pollutant.The research contents are as follows:Poly?ionic liquid?1-vinyl-3-ethylimidazolium bistrifluoromethylsulfonimide salt?Poly?ViEtIm⁺Tf₂N^-??was synthesized by radical polymerization and anion exchange method.Tetracarboxyl cobalt phthalocyanine?CoPc?COOH?₄?was synthesized by phthalic anhydride-urea method.The structures are characterized by FT-IR,UV-Vis,¹H-NMR,elemental analysis,etc.Then,complex PIL/CoPc?x?were synthesized by simple coprecipitation method with different molar ratio of poly?ionic liquid?unit and tetracarboxyl cobalt phthalocyanine,wherein x represents the molar ratio.The resultant complexes PIL/CoPc?x?were characterized by FT-IR,UV-Vis,EDS,XRD,SEM,TEM,BET,contact angle,etc.The results show that the Poly?ViEtIm⁺Tf₂N^-?and CoPc?COOH?₄ have been successfully compounded and the CoPc?COOH?₄ has been uniformly dispersed.In addition,morphology,pore structure and hydrophilicity of the complexes are affected by factors such as anion-cation ratio,solvent,etc.The PIL/CoPc?8?has a certain specific surface area and uniform pore size distribution,which is beneficial to the effective contact between the catalyst and the substrate.Therefore,it is used as a catalyst for the photocatalytic evaluation system for subsequent research and discussion.A 10 mg/L Rhodamine B?RhB?solution was used as a target contaminant to evaluate the photocatalytic performance of the prepared catalyst PIL/CoPc?8?.Firstly,the adsorption-desorption equilibrium between the catalyst PIL/CoPc?8?and RhB was investigated under dark condition,and it was found that the equilibrium time for was 15 minutes.Secondly,the effects of the concentration of catalyst,the concentration of H₂O₂ and the pH of the solution on the degradation of RhB were investigated.The results showed that PIL/CoPc?8?had the best degradation effect on RhB when the concentration of PIL/CoPc?8?was 100 mg/L,the concentration of H₂O₂ was 1.85 mmol/L,and pH of the solution was 7.And the catalytic effect of PIL/CoPc?8?is significantly higher than that of tetracarboxyl cobalt phthalocyanine alone,that is,the introduction of poly?ionic liquid?greatly enhances the catalytic performance of the tetracarboxyl cobalt phthalocyanine.Besides,the catalyst recovery method is simple,and the recovery rate is high.The catalyst has good reusability,and can be reused 4 times.The degradation effects of 10 mg/L methylene blue?MB?and methyl orange?Hln?were investigated by catalyst PIL/CoPc?8?,indicating that the PIL/CoPc?8?is universally suitable for the degradation of dyes.