Removal Of Humus Acid From Leachate By Preparation Of Sheet Carbon Nitride With Melamine

Thermal oxidation can effectively enhance the photocatalysis of graphite-phase carbon nitride（g-C₃N₄）,but its effect on the adsorption performance has not been fully studied,which is crucial for the environmental application of g-C₃N₄ as an adsorbent and photocatalyst.In this study,sheet g-C₃N₄（TCNs）was prepared by thermal oxidation method,and its adsorption of humic acid（HA）and fulvic acid（FA）was systematically evaluated.In this study,melamine was selected as the precursor to prepare massive carbon nitride（BCN）and flake carbon nitride（TCNs）.By characterizing the surface characteristic functional groups,specific surface area,elemental composition and molecular structure of the materials,the structural characteristics of BCN and TCNs were verified.The adsorption properties of four g-C₃N₄ materials prepared by HA were evaluated.The results show that the thermal oxidation method has a significant effect on the adsorption performance of TCNs.The adsorption capacity of BCN for HA is 63.23 mg/g,and the adsorption capacity of TCN-600 for HA can be increased to 145.35 mg/g,that is,TCN-600 prepared at 600℃has excellent humus adsorption potential.The main research contents and conclusions are as follows:（1）By studying the adsorption kinetics,adsorption isotherm,adsorption thermodynamics and water quality influencing factors（pH,alkali metal and alkaline earth metal ions）of HA and FA adsorbed by TCN-600,the adsorption performance and adsorption mechanism were explored.Pseudo-first-order kinetics,pseudo-second-order kinetics and Elovich kinetics models were used to fit the adsorption experimental data.Weber-Morris model was used to fit the internal diffusion mechanism of HA and FA during the adsorption process.The fitting results show that the adsorption of HA and FA by TCN-600 is chemical adsorption,and the adsorption is divided into two steps:HA and FA are first adsorbed on the surface of TCN-600,and then adsorbed on the pores.Freundlich,Langmuir,Sips and Temkin isotherm models were used to fit the adsorption isotherms.Sips model fitting results showed that the maximum adsorption capacity of TCN-600 for HA and FA were 327.88 and 213.58 mg/g,respectively.（2）Analysis results of influencing factors of water quality show that acidic conditions are conducive to adsorption,because the forms of HA and FA will become more compact under acidic conditions,and are easy to be captured by adsorbents.At the same time,the concentration of alkali metals and alkaline earth metals can promote the adsorption of HA and FA by TCN-600.The influence mechanism of pH value,alkali metal and alkaline earth metal on HA and FA adsorption is electrostatic adsorption.In addition,TCN-600 still has a good removal effect on low concentration of humus（0-20 g/L）,indicating its potential application in natural water bodies.（3）TCN-600 not only has a good removal effect on HA and FA components in aqueous solution,but also has a good removal effect on humus in leachate with very complex solution environment.By exploring the adsorption kinetics,adsorption isotherm and influencing factors（pH）of the leachate of TCN-600,it was found that the treatment effect of TCN-600 on the aged leachate was better than that of the fresh leachate,and the treatment effect on the stock solution and nanofiltration concentrate was not much different,and the acidic condition was more favorable for the adsorption of humus in the leachate of TCN-600.The removal rate of aging leachate nanofiltration concentrate by TCN-600 can reach 56.63%,and TCN-600 has a strong ability to remove humus from leachate.（4）The adsorption and removal of humus by TCN-600 was greatly affected by pH,mainly because of the electrostatic force.The alkali metal and alkaline earth metal ions in solution have obvious promoting effect on the adsorption of TCN-600,mainly because of the electrostatic effect,the compression of double electric layer and the effect of cation bridge.Due to the protonation of amino function,it can combine with the oxygen-containing functional group of humus through hydrogen bonding to achieve the removal of humus by TCN-600.In addition,based on the experimental results and the analysis of material before and after adsorption characterization,flake adsorption of humus carbon nitride TCN-600 adsorption mechanism also includesπ-πinteraction.The above results indicate that sheet TCN-600 prepared by thermal oxidation method has a widely application prospect in the adsorption of humus in natural water and wastewater.