The Research Of Step-scheme Photocatalyst G-C₃N₄/TiO₂ For The Degradation Of Tetracycline Hydrochloride Under UV Light

In the fast-developing modern society,new medicines developed by humans meet various needs in agriculture,then a series of pollution problems come along with it.Some antibiotics are metabolized by the human body and still cannot be decomposed,then discharged into the ecological environment.The difficult degradation and toxic nature of antibiotic wastewater have a serious impact and damage on the whole environment.Traditional treatment processes are difficult to remove antibiotics from wastewater.Among various degradation methods,photocatalytic has received wide attention due to its eco-friendliness and ease-preparation.By constructing heterogeneous structures,the electron transport efficiency of photocatalysts can be improved and the electron-hole complexation rate can be suppressed to enhance the redox ability of photocatalysts.In this thesis,the heterojunction photocatalyst g-C₃N₄/TiO₂was prepared by the widely used calcination-ultrasonic synthesis method,and the ability of the composite photocatalyst to degrade tetracycline hydrochloride（TCH）under UV light irradiation was investigated.In this experiment,the heterojunction photocatalyst g-C₃N₄/TiO₂ was prepared by calcination ultrasonic method,and the ability of the heterostructure photocatalyst to degrade tetracycline hydrochloride（TCH）under UV light irradiation was investigated.The morphology,structural characteristics,chemical bonding,specific surface area and light absorption capacity of photocatalysts were analyzed by various characterization methods.The research provides reasonable data support for the application of photocatalysts to antibiotic degradation.In this thesis,heterostructure photocatalysts with different g-C₃N₄mass ratios were prepared,and the adsorption-desorption equilibrium time was determined by dark reaction,excluding the influence of tetracycline hydrochloride self-decomposition.Then,the photocatalytic activity test was carried out on the prepared photocatalyst,and the target pollutant was TCH.The heterostructure photocatalyst with the optimal mass ratio was reported.On this basis,the photocatalyst activity was compared with the precursors g-C₃N₄ and TiO₂.At the same time,the reacted materials were collected for cycle research to test the reusability of the photocatalyst.After that,the morphology of the samples was observed by SEM characterization.The characteristic crystal phase of the samples was verified by XRD characterization and the bonding state of the samples was analyzed by XPS characterization.The light absorption capacity,specific surface area and photogenerated electron-hole separation efficiency of the photocatalyst were investigated by UV-Vis,BET and PL characterization methods.Finally,the photocatalytic mechanism was analyzed by photocatalyst active radical trapping experiments and XPS.In addition to this,the optimal environmental factors during the reaction were also studied.The research results show that:1)The g-C₃N₄/TiO₂-4 photocatalyst with a mass ratio of 4%showed 96.5%degradation efficiency within 90min and the reaction rate constant k was 0.057 min^-1.2)The photocatalytic degradation of g-C₃N₄/TiO₂-4 is better than the precursors.In the recycling experiment,the photocatalytic efficiency was maintained at 85%after 4cycles.3)The SEM results of the samples showed the typical g-C₃N₄layered stacking structure with TiO₂ uniformly dispersed on the surface.XRD results showed the typical g-C₃N₄（002）,anatase（101）and rutile（110）phase.The results of TEM confirmed the analysis of XRD.4)Both superoxide radicals and photogenerated holes play key roles in the photocatalytic process.Based on the assumption of Professor Yu Jiaguo of the Wuhan University of Technology,the transmission path of electrons is S-scheme.5)The optimal dosage of photocatalyst in the reaction is 50mg/L,the optimal environmental p H of TCH is neutral and acidic,and the optimal initial concentration of TCH is 30 mg/L.