Preparation Of Platanus Acerifolia Fiber Based Photocatalytic Composites And Their Performance In The Removal Of Cr(Ⅵ) From Water

The settlement of heavy metal pollution in water is one of the research hotspots in the field of environmental science and engineering.Cr（Ⅵ）has been considered toxic due to great mobility,undegradability and bioaccumulation in environment.Being teratogenic,carcinogenic,mutagenic and biotoxic,it throws great threat on human health and ecological environment.Among treatment technologies for the removal of Cr（Ⅵ）,photocatalysis is highlighted because of non-toxicity,safety,stability,high catalytic activity and low energy consumption.In this paper,pre-treated Platanus acerifolia fibers（ae-PAF）were utilized as carriers for photocatalysts,and three photocatalytic composites were prepared via different experimental methods,includingα-Fe OOH@ae-PAF,Po PD@ae-PAF and r GO-TiO₂@ae-PAF.Based on the characterization of physical and chemical properties of the photocatalytic composites,the samples’performance in the removal of Cr（Ⅵ）from water and photocatalytic conditions were annalyzed.And the mechanism for the efficient Cr（Ⅵ）removal in water with photocatalytic composites based on Platanus acerifolia fibers（PAF）was explored preliminarily.The main research contents are as follows:（1）α-FeOOH was successfully loaded on the surface of ae-PAF by one-step hydrothermal method.SEM showed thatα-Fe OOH@ae-PAF maintained the hollow tubular structure of PAF.The photocalatytic experiment results showed that Cr（VI）removal rate reached as high as 99.47%when 10 mgα-Fe OOH@ae-PAF withα-Fe OOH content at 20%was employed in 50 ml potassium dichromate solution at p H 2 with initial concentration of20 mg·L^-1,and the system was irradiated under UV-light for 70 min at 40℃.The study confirmed the successive pretreatment by Na OH and cellulase removed wax and cellulose from Platanus acerifolia fibers（PAF）.The superior adsorption capacity for Cr（Ⅲ）of ae-PAF prompted the synergy effect between the photocatalytic reduction of Cr（Ⅵ）and the adsorption of Cr（Ⅲ）,which enhanced the photocatalytic removal efficiency of Cr（Ⅵ）from water.（2）PoPD@ae-PAF was obtained through the loading of PoPD on the surface of ae-PAF via in-situ polymerization of o-phenylenediamine initiated by ultraviolet light.On the basis of single factor experiments,BP neural network was applied to optimize the photocatalytic conditions and the result showed that the Cr（VI）removal rate reached 99.6%under optimum conditions at p H=1.8,30℃and 15 mg·L^-1.The experiment results indicated the significant increase of electrical conductivity of Po PD@ae-PAF in transient photocurrent test due to the load of Po PD on ae-PAF,which verified Po PD contributed to the photocatalytic reduction efficiency of Po PD@ae-PAF because Po PD boosted the photogenerated charge transfer during the photocatalytic process.Based on the different adsorption capacity of ae-PAF for Cr（Ⅲ）and Cr（Ⅵ）,it was concluded that the the synergy effect between the photocatalytic reduction of Cr（Ⅵ）and adsorption transfer of Cr（Ⅲ）significantly enchanced the photocatalytic removal efficient of Cr（Ⅵ）from water.（3）Taking TiO₂ as photocatalyst,we prepared r GO-TiO₂@ae-PAF by simultaneous loading reduced graphene oxide（rGO）and TiO₂ nanoparticles on the surface of ae-PAF via one-step hydrothermal method.Characterization techniques,including SEM,TEM,XRD,FT-IR,and etc.,were utilized to investigate the changes of sample before and after the load of r GO and TiO₂ nanoparticles.It was shown in transient photocurrent analysis that r GO facilitated the transfer of photogenerated electrons and inhibited the recombination of photo-induced carriers.Adsorption experiments proved that the adsorption capacity of r GO-TiO₂@ae-PAF for Cr（Ⅲ）is prominently better than Cr（Ⅵ）.According to the Cr（VI）adsorption and photocatalytic reduction performance of samples,the ae-PAF’s predominant adsorption for Cr（Ⅲ）contributed to the synergy between photocatalytic reduction of Cr（Ⅵ）and adsorption transfer of Cr（Ⅲ）,improving the photocatalytic removal performance of Cr（Ⅵ）from water.The thesis made full use of the structural features and adsorption capacity of PAF which was deemed natural fiber waste,prepared three kinds of PAF based photocatalytic composites,and evaluated their performance in the removal of Cr（Ⅵ）from water.Through the combination of biological characteristics of natural fibers and advantages of photocatalysis technology,three as-obtained photocatalytic composites benifited from the design and preparation of material structure and showed remarkable efficiency in the removal of Cr（Ⅵ）from water by the synergy of adsorption/photocatalysis.It not only carried out beneficial practice for the PAF resource utilization,but also demonstrated ideas and exploration for the address of Cr（VI）pollution in water with aid of recycled waste.