Preparation And Photocatalytic Properties Of Spinel-type ZnFe₂O₄

Photocatalytic degradation of organic pollutants is becoming one of themost promising green chemistry technologies. Spinel-typed ZnFe₂O₄has beenapplied widely in the dye wastewater degradation, owing its higherphotocatalytic activity and magnetic property, without secondary pollution. Manyresearchers have a great interest. The past experiment results show that theactivity of ZnFe₂O₄synthesized was lower under UV irradiation. The ZnFe₂O₄-doped which has narrower band can enhance the ferrite’s photocatalytic activityand the ability of absorbing light.In this paper, the band of ZnFe₂O₄and the doped ZnFe₂O₄were studied bythe first-principle using Castep software. And the ferrites which doped Co²⁺,Mg²⁺, Cu²⁺, Ba²⁺, Sm³⁺, La³⁺, Y³⁺and Nd³⁺was synthesized through Sol-Gelmethod, using fresh egg white as a complexing agent. The radius of Co²⁺, Mg²⁺,Cu²⁺is less than Zn²⁺and Fe³⁺’, they were doped into the tetrahedron, displaceZn²⁺. The radius of Ba²⁺, Sm³⁺, La³⁺, Y³⁺, Nd³⁺is more than Zn²⁺and Fe³⁺’, theywere doped into the octahedron. The XRD results show the ZnFe₂O₄and thedoped ZnFe₂O₄were pure, only with the spinel structure, and diffraction peak hasno skewing. The SEM results reveal that the ZnFe₂O₄and the doped ZnFe₂O₄crystalline grains presented irregular shapes and the crystal boundary of schorlgrown well. The synthesized sample was used as the catalyst for the discolorationof methyl orange （MO） in solution under UV irradiation. And the photo-catalyticexperimental results revealed that MO could be efficiently discolored by ferrite.The photo-catalysis of the ferrite which doped Mg²⁺was higher than doped Co²⁺, Cu²⁺, Ba²⁺. And, compared with the other trivalent ions, the ferrite doped La³⁺had the best catalytic activity. It was been known that using pure ZnFe₂O₄, Mg_0.1Zn_0.9Fe₂O₄and Zn La_0.2Fe_1.8O₄as photo-catalysis, the MO discoloration ratiowas75.75%,81.71%and82.72%, respectively.ZnLa_0.2Fe_1.8O₄with different morphologies was synthesized by differentmethod. The synthesis conditions, structures, morphologies and thephotocatalytic properties were investigated. The experiment results reveal thatthe ZnLa_0.2Fe_1.8O₄with rodlike structure by hydrothermal method wassynthesized. Spinel-typed ZnLa_0.2Fe_1.8O₄with octahedral structure wassynthesized through sol-gel method. Sol-gel auto-combustion method cansynthesize the ferrite with stratified structure. And the ZnLa_0.2Fe_1.8O₄withirregular sphere structure would be obtained using the oxalate-coprecipitationmethod. We can know that using the ZnLa_0.2Fe_1.8O₄with rodlike structure,octahedral structure, stratified structure and columnar structure degrade MO, theMO discoloration ratio was86.37%,82.72%,65.15%,67.45%, respectively.