Study On Photocatalytic Properties Of UiO-66-X Modified Znln₂S₄ Supported Heterojunction Composites

Tetracycline hydrochloride and rhodamine B are common pollutants in industrial production and daily life,which are difficult to be degraded by basic wastewater treatment processes due to their structural stability and biological toxicity in water bodies,and pose a threat to human life and health when they are released into water bodies.The use of solar photocatalysis to degrade the above pollutants is one of the more feasible strategies.In this paper,a series of UiO-66-X modified Znln₂S₄ loaded photocatalytic composites were synthesized using graphite felt（GF）as the loading center,and detailed characterization and density flooding theory（DFT）calculations were performed to optimize the material synthesis and reaction conditions to enhance the photocatalytic performance and explore the photocatalytic reaction mechanism.The conclusions are as follows:（1）UiO-66/Znln₂S₄ heterojunction photocatalyst was synthesized on calcined graphite felt（C-GF）by hydrothermal method,and ZIS and UiO-66 were synthesized on C-GF by characterization methods such as structure,morphology and chemical composition.The surface was successfully compounded.After using UiO-66 to modify ZIS,the light absorption performance,adsorption performance and electrochemical performance of the composite material are all improved.The supported catalyst has high degradation activity to tetracycline hydrochloride（TCH）.When the mass ratio of UiO-66and ZIS was 10%,the initial solution p H=5,the TCH concentration was 10 mg/L,and no humic acid was present,the photocatalytic removal of TCH was the best,reaching 97.0%.At the same time,it showed strong stability in five consecutive cycle experiments.In addition,comparative experiments were carried out under sunlight,and the degradation products under different conditions were analyzed and predicted for toxicity.The results showed that ZU-10/C-CF also had a high removal rate（96.3%）and could effectively reduce the risk of toxicity in water.（2）According to the mechanism analysis,O2^-is the main active substance in the photocatalytic process,and OH and h⁺play an auxiliary role.The construction of UiO-66 and ZIS heterojunction promotes the generation of active free radicals.DFT calculation results show that UiO-66 and ZIS can spontaneously form a built-in electric field and construct an S-type heterojunction,which effectively promotes the photo-induced electron transfer,reduces the recombination rate of carriers and improves the photocatalytic activity.（3）Different ligand modified UiO-66-X（X=H,NH₂,（OH）₂,Br）modified Znln2S4 supported on hydrophilic graphite felt（H-GF）was synthesized,and the effects of ligand modification on the properties of the material were studied.The characterization results show that the crystal structure and surface morphology of UiO-66-X/Znln₂S₄/H-GF with different ligands are not significantly different,but the light absorption and electrochemical properties of the modified composites are significantly improved.Four UiO-66-X/Znln₂S₄/H-GF have good adsorbability to cationic dye Rh B,whereas they have poor adsorbability to anionic dye methyl orange（MO）.The photocatalytic degradation ability of all materials modified by ligands is higher than that of unmodified materials The analysis shows that the difference of electronegativity of composites and steric hindrance of groups are the main factors affecting adsorption.The electronic effect and improved light absorption of groups mainly affect photocatalytic activity.Among them,electron-donating groups（amino and hydroxyl）can increase the electron cloud density of the reactive center,promote the separation and transfer of photogenerated electrons and holes,and make the composite material have better photocatalytic performance.