Modification Of ZnO/Chitin Hydrogel Composite Catalyst And Its Application In Dye Photodegradation

A novel nano ZnO-GO/CGH was prepared using an in-situ synthesis process for the photodegrade of methylene blue under the illumination of visible light.The chitin hydrogel was utilized to provide uniform binding of the nano ZnO–GO to the hydrogel surface and to prevent their agglomeration.GO provides multi-dimensional protons and electron transport channels for ZnO with a flower-like structure,which possessed improved photo-catalytic activity.SEM analysis indicates that the hydrogel has good adsorption properties with rougher surfaces and porous microstructure,which makes it adsorb the dyes effectively.Under synergetic effects of adsorption and photo-catalysis,the catalytic efficiency and recycling of nano ZnO–GO/CGH were greatly improved.Synthesized nano ZnO–GO/CGH showed high dye removal efficiency of 99%,about 2.2 times as that of the pure chitin gel under the same condition.It suggests the potential application of the ZnO-GO/CGH composites to remove organic dyes from wastewater.Some main results were concluded as follows:(1)The composite materials of ZnO/CGH and ZnO-GO/CGH were prepared by an in-situ synthesis process.SEM showed that ZnO-GO/CGH has a 3D porous network structure piled up a flower-like shape with interconnected pores composed of ZnO-GO nanosheetse,and the remaining pores were conducive to improving the adsorption capacity of the composite.TEM shows that ZnO grows along the(101)crystal plane in the chitin graphene hydrogel with a lattice distance of about 0.25 nm.XRD showed that the chitosan graphene hydrogel with ZnO-GO did not change the crystal plane of ZnO.Raman spectroscopy shows that,compared with GO,the Raman spectroscopy of ZnO-GO/CGH has a slight blue shift,which may indicate that ZnO-GO and CGH produce surface hybridization during the interaction.XPS showed that part of GO was reduced after the composite reaction.The oxygen-containing functional groups that have not been completely removed make ZnO-GO/ CGH have good hydrophilicity and help the purification of composite hydrogel in water.(2)The effect of ZnO-GO/CGH on MB removal under visible light was investigated,and the factors such as the doping amount of the reducing agent VC,ZnO-GO,catalyst dosage,substrate concentration and pH were explored.The 1% ZnO-GO/CGH composite material prepared by VC reducing agent was selected as the catalyst to determine the optimal reaction conditions under visible light: Under visible light,1 g/L of 1% ZnO-GO/CGH composite material,after acting on 100 mL,30 mg/L and pH 7.0 MB solution for 6 h,MB removal rate can reach 99%.Compared with ZnO/CGH,the loading of the catalyst in ZnO-GO/CGH is lower and the stability is better.After 5 times of repeated use,the MB removal rate can still reach 93%,which is still close to the new catalytic material.(3)Compared with ZnO/CGH composite materials,the mechanical strength of ZnO-GO/CGH is also improved by 1.4 ~ 2.43 times,and the overall mechanical strength is in the range of 1.98–18.80 N,which is more conducive to the stability and industrial application of the catalyst,making the catalyst difficult to fall off during the reaction and easy to recycle.The gel swelling experiment found that the compounding process had an effect on the hydrophobicity of the material.The water holding capacity of the gel material was CGH> 3% ZnO/CGH> 1% ZnO–GO/CGH.After adsorption swelling for 30 min,the pure chitin graphene hydrogels were 3.24 and 4.37 times that of 3% ZnO/CGH and 1% ZnO–GO/CGH,respectively,which indicated that the introduction of the catalyst greatly improved the activity of the composite.