Study On Preparation And Adsorption Properties Of Monodisperse Carbon Nanospheres And Their Composite Membranes

Dye wastewater is a common and important pollution problem,and the discharge is increasing,which has a great impact on our daily life.There is an urgent need to develop a new and effective adsorbent.In this thesis,a simple and effective green synthesis route was adopted,using glucose as carbon source and water as solvent to prepare monodisperse carbon nanospheres(CNs)in a hydrothermal reaction system to study the dye adsorption properties.By introducing anionic polyacrylamide(APAM)into the hydrothermal system,CNsAPAM with high yield was synthesized from glucose and used to adsorb organic dye methylene blue(MB).The research shows that APAM,as an additive to assist the synthesis of hydrothermal CNs,can effectively improve the yield of CNs,with the maximum yield can reach 21.5%.APAM is an anionic additive.Its molecular chain contains polar groups,which can play the role of adsorption and achieve the purpose of purifying wastewater.And MB is a cationic dye.Therefore,the introduction of APAM can promote the adsorption of MB dye and effectively improve the adsorption performance of CNs.PAA-g-CNs is prepared by grafting acrylic acid(AA)containing hydrophilic groups onto the surface of CNs through in-situ polymerization,and then polymerized under the action of ammonium sulfate(APS)initiator.This not only improves the hydrophilicity of CNs,but also increases the adsorption sites of dyes,so as to enhance the adsorption performance of dyes.After a series of characterization tests.We analyzed the surface morphology,chemical composition and dispersion of PAA-g-CNs.The results showed that AA was successfully grafted onto the surface of CNs,and the results of dispersion showed that the hydrophilicity of CNs was significantly improved.The adsorption experiment of PAA-g-CNs on MB showed that the introduction of hydrophilic groups effectively improved the adsorption capacity of MB,up to 185.9 mg/g.PAA-g-CNs/PVDF composite membrane was prepared by blending with polyvinylidene fluoride(PVDF)on the basis of PAA-g-CNs.The results show that the continuous increase of PAA-g-CNs will lead to the surface roughness of PVDF membrane.For the cross-sectional SEM analysis,all PVDF membranes have asymmetric structure.The addition of PAA-g-CNs can not only improve the exchange rate of solvent and water,but also help to improve the porosity of the membrane.Moreover,the hydrophilicity and mechanical properties of PAA-g-CNs/PVDF composite membrane have been improved.By studying the adsorption experiment of PAA-g-CNs/PVDF composite membrane on MB,the adsorption conditions were optimized,and the maximum adsorption capacity of MB was6.4 mg/g.The results of adsorption kinetics and isothermal adsorption analysis show that: the adsorption processes of CNs-APAM,PAA-g-CNs and PAA-g-CNs/PVDF composite membranes were relatively consistent with the pseudo-second-order kinetic model and the Langmuir model.