Preparation Of Carbon-based Composite And Its Application In Wastewater Purification

Fenton system has been widely used in the treatment of organic wastewater ousing to its advantages of strong oxidation ability（·OH）fast reaction rate and mild reaction condition.However,the traditional Fenton reaction also has several shortcomings such as a narrow suitable p H（p H=2-4）,limited catalytic ability of free Fe²⁺ion,deactivation and reutilization difficult of external H₂O₂.In this paper,a novel and efficient carbon-based composite heterogeneous photocatalyst was successfully prepared based on carbon materials to construct graphitic carbon nitride/reduced graphene（g-C₃N₄/r GO）,three-dimensional ordered macroporousα-Fe₂O₃/graphene aerogel（3DOMα-Fe₂O₃/GA）andα-Fe₂O₃/orange biochar（α-Fe₂O₃/OC）solar photo-Fenton system.Due to its excellent electron mobility,high specific surface area and carbon-based materials could enhance the light harvesting efficiency,suppress charge recombination and improve the stability of photo-reponses,which making more photo-generated electrons（e^-）participate in Fenton reaction and more holes（h⁺）proceed the direct oxidation.At the same time,it enhanced the photo-Fenton activites towards organic pollutants,realized the photo-Fenton with self-supplied H₂O₂ and recycled the catalyst after the reaction.The main contents and results were as follows:1)Heterogeneous solar photo-Fenton degradation of Rh B over g-C₃N₄/r GO catalyst with self-synthesizing H₂O₂The g-C₃N₄/r GO catalyst was fabricated rationally by hydrothermal calcination method using melamine and r GO as raw materials.The results demonstrated that 58 mmol/L amount with self-supplied H₂O₂ and 87%degradation of Rh B was achieved in 120 min under the optimum conditions:p H=3.5 and loading 15%the amount of r GO.It was attributed to the fact that the g-C₃N₄ absorbed amounts of photons with enough energy,the photo-generated electrons in the CB of g-C₃N₄ transfered into the r GO,consequently improving the electron-hole separation and inhibiting self recombination of photo-generated charge carries.As the same time,the holes proceeds the direct oxidation in the VB of a g-C₃N₄ and the electrons on r GO were reduced by two-electron reduction of O₂ to selectively produce H₂O₂ oxidation Fe²⁺for organic contaminants removal mainly triggered by the solar photo-Fenton process.2)Heterogeneous neutral solar photo-electro-Fenton degradation of Rh B over 3DOMα-Fe₂O₃/GA catalystThe 3DOMα-Fe₂O₃/GA electrode was fabricated rationally by vertical impregnation,solvent evaporation and template calcination.The results showed that 34 mmol/L amount with self-supplied H₂O₂ and 96.8%degradation of Rh B was achieved in 60 min under the optimum conditions:p H=7.It was attributed to the fact that the 3DOMα-Fe₂O₃ absorbed amounts of photons with enough energy under the action of multiple scattering and slow photo effect,the photo-generated electrons in the CB ofα-Fe₂O₃ transfered into the GA surface,consequently improving the electron-hole separation and inhibiting self recombination of photo-generated charge carries.As the same time,the holes proceeds the direct oxidation in the VB ofα-Fe₂O₃ and the electrons on GA surface were reduced by two-electron reduction of O₂ to selectively produce H₂O₂ oxidation Fe^Ⅱ/Fe^Ⅲfor organic contaminants removal mainly triggered by the solar photo-electro-Fenton process.3)Heterogeneous solar photo-Fenton degradation of MO over biochar enhancedα-Fe₂O₃catalystTheα-Fe₂O₃/OC catalyst was fabricated rationally by coprecipitation-oxygen limited and temperature controlled-calcination method.The results exhibited that 97%degradation of MO was achieved in 80 min under the optimum conditions:p H=3 and the mass ratio of 1:1（C:Fe）.It was attributed to the fact that theα-Fe₂O₃ absorbed amounts of photons with enough energy,the photo-generated electrons in the CB ofα-Fe₂O₃ transfered into the OC,consequently improving the electron-hole separation and inhibiting self recombination of photo-generated charge carries.As the same time,the holes proceedd the direct oxidation in the VB ofα-Fe₂O₃ and the electrons on OC assisted nanocrystalsα-Fe₂O₃ to catalyze H₂O₂ for organic contaminants removal mainly triggered by the solar photo-Fenton process.4)Polyethylenimine modified bamboo biochar adsorbent（PEI@BC）for highly effective adsorption of heavy metal ionsMuch more attention has been paid to biochar for improved heavy metal wastewater treatment due to large porocity,huge specific surface area and being rich in oxygen-containing functional groups.The PEI was grafted onto the BC substrate via the cross-linking reaction,which improved the adsorption capacity of BC for heavy metal pollutants.The results demonstrated that the kinetics suited the pseudo-second-order model better and the equilibrium date well fitted the Langmuir model,with adsorption capacities of 54.2,106.64 and 80.58 mg·g^-1 for Cu²⁺,Pb²⁺and Cd²⁺within 6 h.It was attributed to the fact that the PEI grafted onto the BC provided a large number of amine groups,which could react with heavy matal ions in static electricity or complexation.As the same time,the BC increased adsorption sites with higher metal sorption capacity after PEI modification.