Synthesis Of Triazine-based Environmental Functional Materials And Their Adsorption Properties

With the rapid development of technology and industry,a variety of the environmental pollution becomes more and more serious.The water pollution has been one of the main environment problems.Adsorption method can be applied to water purification because of its advantages of simple operation,low cost,high biocompatibility,easily regenerable,etc.Triazine ring is a electron-deficient aromatic system with high nitrogen content.Triazine can act as Lewis base and has superior functions of metal coordination,?-?interaction,forming hydrogen bond,etc.Therefore,many researchers are committed to introducing the triazine structure into the adsorbents,so that the functional materials can be used for removal of toxic heavy metal ions and organic pollutants from water.In this thesis,two triazine-based functional adsorbents which are mesoporous poly?melamine-formaldehyde??mPMF?and carbon nitride were synthesized and characterized by the low-cost triazine-based monomer—melamine?MA?.And the triazine-based adsorbents were used to study its adsorption properties and mechanisms on various water contaminants.The main results are as follows:1.The effects of various parameters?such as solvents,time,temperature,concentration of reactants,etc.?on solvothermal synthesis of mPMF were optimized.mPMF was successfully synthesized in MEG for the first time according the following procedure:The mixture of melamine?6 mmol?,paraformaldehyde?10.8 mmol?,and MEG?6.8 mL?was heated at 120°C for 1 h,and then magnetically stirred for about 10 min to homogenize it.The whole mixture reacted at 170°C for 48 h to form mPMF.The mPMF was sequentially washed with ethanol?10 mL?,deionized water?15 mL,50°C?and ethanol?10 mL?,recovered by centrifugation and dried at 100°C for 24 h before characterization and adsorption tests.The product was characterized by XRD,SEM,IR,BET,TGAandelementalanalysistobespongymesoporous poly?melamine-formaldehyde?.This synthesis procedure has the advantages of low-cost raw material,simple operation process and reaction conditions,no pungent smell,environment friendly,suitable for large-scale production,and the product is nitrogen-rich with no sulfur impurity.The product application as a versatile adsorbent for wastewater treatment has been demonstrated by the adsorption of various water contaminants.2.The effects of various parameters?such as precursors,reaction atmosphere,reaction medium,time and temperature,etc.?on molten salt synthesis of carbon nitride were optimized.Carbon nitride was successfully synthesized in molten salt via the following procedure:Melamine was mixed with a eutectic mixture of LiCl and KCl.The mixture was heated in a tube furnace at a ramping rate of 4.8 ^oC/min under N₂ atmosphere and kept at500 ^oC for 3 h.The sample was washed liberally with boiling water,recovered by centrifugation and dried at 100°C for 12 h before characterization and adsorption tests.The product was characterized by XRD,SEM,IR,BET,and elemental analysis to be graphite-type carbon nitride with special morphology.The effects of various factors?such as adsorption time,pH,temperature,initial concentration of solution,etc.?on the adsorption properties of MA-LiKCl-500T-3 were studied by static adsorption using methylene blue?MB?as a model pollutant.The results showed that when the initial concentration of MB was 90 mg/L,pH was 7.0 and the temperature was 25 ^oC,the adsorption equilibrium time is 4 h,and the adsorption capacity was 94.1 mg/g.The increase in the temperature would benefit the adsorption,and the maximum adsorption capacity of MB was up to 130.9 mg/g,and the adsorption process can be fitted with the Freundlich isotherm.The MA-LiKCl-500T-3 could be regenerated for reuse by washing with ethanol or hydrogen peroxide which indicates that MA-LiKCl-500T-3 has the potential to be developed for pratical applications.