Preparation Of Three-Dimensional Porous CuFe₂O₄-Based Heterojunction Materials And Their Peroxymonosulfate Activation Properties Under Visible-Light

High-efficiency,energy-saving,and environmentally friendly wastewater treatment technology is essential to solve the increasingly serious water environment pollution problem.Co-activation of peroxymonosulfate（PMS）by catalyst-visible light can generate strong oxidation-active radicals(SO₄^·-),which is an important way to solve organic pollution in water bodies.As a bimetallic oxide semiconductor catalyst,copper ferrate（CuFe₂O₄）can both co-activate PMS by using surface bimetallic ions and directly activate PMS by generating photogenerated electrons through visible light,which can generate strong oxidation-active radicals SO₄^·-,and it is one of the ideal materials to realize photoexcited PMS for degradation of organic pollutants in water.It is one of the ideal materials to achieve photo-excited PMS degradation of organic pollutants in water.However,CuFe₂O₄materials still face the following problems in application:firstly,CuFe₂O₄nanoparticles are easily agglomerated in the reaction process due to their high surface energy,which leads to the reduction of reactive sites;secondly,single-component CuFe₂O₄materials are easily compounded by photogenerated electron-hole pairs,resulting in the low catalytic activity of photoactivated PMS.For the above problems,CuFe₂O₄with a three-dimensional macroscopic porous structure and CuO/CuFe₂O₄,Ag/CuFe₂O₄,Ag/CuO/CuFe₂O₄heterojunction materials were prepared by polymer-assisted freeze-drying method.By constructing macroscopic three-dimensional porous structures,the problem of easy aggregation of nanoparticles and the improvement of reaction mass transfer performance is improved;by constructing CuFe₂O₄-based binary and ternary heterojunctions,the effective separation of photogenerated electron-hole pairs is enhanced,the activation process of PMS is promoted,and the catalytic activity is improved.The details of the study are as follows:（1）Preparation of three-dimensional porous CuFe₂O₄and its performance of visible light-activated PMS to degrade organic pollutants.CuFe₂O₄three-dimensional porous materials were prepared by polymer-assisted freeze-drying and high-temperature calcination treatment.Meanwhile,CuFe₂O₄nanoparticles were prepared under the condition of polymer-assisted direct drying.The experimental study of three-dimensional porous CuFe₂O₄（10 mg）activated PMS（10 mg）under visible light to degrade tetracycline hydrochloride（TCH 20 ppm 40 m L）shows that three-dimensional porous CuFe₂O₄has a larger first-order reaction kinetic rate constant,which is CuFe₂O₄nanoparticles 2.2 times.Its three-dimensional connected porous network structure is conducive to mass transfer,the high specific surface area can provide more active sites and improve the catalytic activity of activated PMS,and the macroscopic self-supporting structure is conducive to the separation and recycling of samples after the reaction.（2）Controllable fabrication of CuO/CuFe₂O₄three-dimensional porous heterojunction and its visible light-activated PMS degradation performance of organic pollutants.A series of CuO/CuFe₂O₄heterojunctions were fabricated by changing the ratio of copper salts to iron salts in the precursor solution during the freeze-drying process.An experimental study of CuO/CuFe₂O₄（10 mg）in visible light-activated PMS（10 mg）degradation of TCH（20 ppm 80m L）showed that the reaction rate constants of CuO/CuFe₂O₄heterojunctions were 4.9 and 9.8times higher than those of single-component CuFe₂O₄and CuO,respectively.Through the mechanism study,it was found that the heterojunction material can promote the separation of photo-thermal electron holes and then promote the activation process of PMS on the surface of CuFe₂O₄,generate more strong oxide radicals SO₄^·-,improve the catalytic activity,and inhibit the metal ions of Cu（152.9μg/L）and Fe（4.3μg/L）overflow.In addition,the macroscopic self-supporting structure of CuO/CuFe₂O₄facilitates the separation and reuse of samples from the reaction solution.（3）Controllable preparation of Ag/CuFe₂O₄three-dimensional porous heterojunction and its（10 mg）activation of PMS（10 mg）under visible light to degrade TCH（40 ppm 80 m L）.A series of Ag/CuFe₂O₄three-dimensional porous heterojunction materials were prepared by introducing different amounts of silver salts into the precursor solution during the freeze-drying process.Experimental studies show that the Ag/CuFe₂O₄heterojunction can also promote the separation of photogenerated carriers.The reaction rate constant of activating PMS to degrade TCH under visible light is 2.2 times that of single-component CuFe₂O₄.In addition,through the mechanism study,it was found that the photogenerated electrons in the Ag/CuFe₂O₄heterojunction were transferred to Ag,which in turn promoted the activation process of PMS on the Ag surface.It effectively inhibited the metal ions of Cu（256.1μg/L）and Fe（1.8μg/L）overflow.Surface reactions and spills.The macroscopic self-supporting structure of Ag/CuFe₂O₄is beneficial for recycling in practical applications.（4）Preparation of Ag/CuO/CuFe₂O₄three-dimensional porous heterojunction and study of the properties of activated PMS to degrade organic pollutants under visible light.Ag/CuO/CuFe₂O₄ternary heterojunction materials were prepared by changing the content of silver nitrate in the precursor solution during the freeze-drying process.The results show that the reaction rate constants of Ag/CuO/CuFe₂O₄（10 mg）ternary heterojunction in visible light-activated PMS（10 mg）degradation of TCH（40 ppm 80 m L）are the 7.1 and 3.9 times than binary heterojunction CuO/CuFe₂O₄and Ag/CuFe₂O₄.Mechanistic studies show that the Ag/CuO/CuFe₂O₄ternary heterojunction further improves the separation of photogenerated electrons and holes,the multi-element interface promotes the transfer of photogenerated electrons to the Ag surface,improves the activation process of PMS,and significantly inhibits the Cu（112.0μg/L）and Fe（1.6μg/L）surface reaction and spillover.The self-supporting structure of Ag/CuO/CuFe₂O₄is beneficial to the separation and recovery of samples and has good recyclability.