| As an advanced catalytic oxidation technology,the semiconductor photocatalytic technique oxidation can effectively degrade the organic pollutants.It is known that graphitic carbon nitride(g-C3N4),an n-type semiconductor with a narrow bandgap of 2.7 eV,has been widely studied as a visible light driven photocatalyst for organic pollutant degradation,while attapulgite exhibits strong surface activity and adsorption capacity and can be used as support for catalysts.In this dissertation,we demonstrate a simple and straightforward strategy to fabricate g-C3N4/attapulgite composite,and on this basis,which was further hybridized with Ag、Pt nanoparticles and polyaniline(PANI),respectively.The resulting hybrid catalysts were characterized by XRD、SEM、TEM、XPS、BET、UV-Vis、PL、EIS and adsorption experiments,while the photocatalytic activity of the catalysts was evaluated by the degradation of methyl orange(MO)under visible light irradiation The main contributions of this dissertation are described as follows:(1)Ppreparation and photocatalytic performance of ATP/g-C3N4The thin g-C3N4 layers were loaded onto the surface of the pretreated attapulgite(grafted by(3-glycidyloxypropyl)trimethoxysilane(KH560))to form ATP/g-C3N4 hybrid photocatalyst by in-situ deposition,freeze drying and calcination.Results showed that the g-C3N4thin layers are uniformly loaded onto the ATP surface via the chemical bond(Si-O-C),which is beneficial to tailor the surface electronic structure of g-C3N4 and provide more active sites.The morphology of the original attapulgite can be effectively maintained after hybridization and the specific surface area was obviously increased.Methyl orange(MO)was used as the model system to investigate the photocatalytic activity and the ATP/g-C3N4 composite photocatalyst exhibited excellent performance,which is far superior to that of ATP or g-C3N4 alone due to the concerted effect.Moreover,ATP/g-C3N4 could be readily keep highly degradation ratio after 4 cycles.(2)The ATP/g-C3N4-Ag systemThe ATP/g-C3N4-Ag hybrid photocatalyst was successfully obtained by depositing Ag nanoparticles with average size of～6.54 nm onto the surface of ATP/g-C3N4 via a simple reduction reaction.The evaluation results of photocatalytic performance for ATP/g-C3N4-Ag showed that the activity was obviously enhanced after the introduction of Ag nanoparticles as compared with pure g-C3N4 and ATP/g-C3N4.The degradation rate of 10 mg L-1 methyl orange was achieved up to 96.1%within 20 min,nearly 2.5 times greater than that of ATP/g-C3N4.Moreover,the high degradation ratio of ATP/g-C3N4-Ag-4 can be keeped after 4 cycles.The trapping experiments showed that ·OH and ·O2-are the main active species in the photocatalytic process.(3)The ATP/g-C3N4-Pt/PANI systemThe ATP/g-C3N4-Pt/PANI was successfully prepared by depositing Pt nanoparticles onto the surface of ATP/g-C3N4 via simple reduction reaction,followed by the polymerization of aniline on the surface of ATP/g-C3N4-Pt using Pt nanoparticles as catalyst in acid solution.The adsorption behavior of anionic dye(MO)in aqueous solution on AIP/g-C3N4-Pt/PANI was investigated.The adsorption experiments were carried out under different conditions(varying MO concentrations、temperatures and pH values).MO was also used as the model system to investigate the photocatalytic activity of the obtained products.The results showed that the composite exhibited excellent adsorption performance.The static adsorption kinetics data were fitted well to the pseudo-second-order kinetic model.Adsorption isotherm can be described by the Langmuir isotherm equation.The photocatalytic degradation of MO under visible light irradiation was also investigated.Results showed that conjugated structures of PANI and g-C3N4 were well maintained in the hybrid,implying the good compatibility.The photocatalyst showed remarkable visible-light photoactivity because of the synergistic effect between multicomponent materials.The decomposition rate of 20 mg L-1 MO was achieved to 96.3%within 80 min by using ATP/g-C3N4-Pt/PANI as the photocatalyst,almost 1.5 times than that of ATP/g-C3N4. |
