Preparation Of Chitosan Composites And Its Adsorption Mechanism For Ionic Dyes In Wastewater

At present,the environmental problems caused by dyeing wastewater are getting more and more serious.The dyes in the wastewater are difficult to degrade organic matter,and it is difficult to remove them effectively by traditional biological treatment methods.The dye of waste water is also a kind of available resource.The method of adsorption can be used to recycle the dye of waste water effectively.Chitosan has been widely used in the treatment of dyeing wastewater due to its wide sources and rich adsorption functional groups.In this study,a new and efficient adsorption material was synthesized based on chitosan.This study prepared activated alumina in the laboratory,and then used the method of crosslinking to load the chitosan on the surface of the activated alumina,and used the method of impregnation method to modified Chitosan@Al₂O₃ by cationic surfactant CTAB.The physicochemical properties of CTAB-Chitosan@Al₂O₃ were analyzed by means of Fourier infrared spectroscopy（FTIR）,Field Emission Scanning Electron Mcroscope（SEM）,X-ray photoelectron spectroscopy（XPS）,Thermogravimetric analysis（TGA）,X-ray diffraction（XRD）,automatic rapid specific surface and porosity analyzer（BET）,and zeta potential measurement.It can be seen from the characterization results that:（1）from the Thermogravimetric analysis and TOC analysis,it can be found that the material has a strong stability at room temperature and under certain hydraulic conditions,and can be used in conventional water treatment engineering;（2）loading onto the surface of alumina and the modification by CTAB both increased the specific surface area and pore diameter of chitosan,and The pore size of the modified composite was micropore and mesoporous.Using the cationic dye（Methylene Blue,Neutral Red and Basic Fuchsine）and anionic dyes（Methyl Orange,Congo Red and Reactive Blue）to study the adsorption capacity of CTAB-Chitosan@Al₂O₃ to dyeing water.Explored the different influence factors（adsorption time,temperature,substrate concentration,p H）of the adsorption of anionic dyes.Temperature,p H and time have different influence to the adsorption when the anionic dyes have different structure.Through the adsorption model to analyze the adsorption kinetics,adsorption isotherm and adsorption thermodynamics of CTAB-Chitosan@Al₂O₃ to three anionic dyes.By Langmuir model,Freundlich model,and monolayer adsorption model of one energy to study the adsorption isotherm of CTAB-Chitosan@Al₂O₃,the results showed that the adsorption of CTAB-Chitosan@Al₂O₃to three anionic dyes conformed to Langmuir model,the adsorption process was single molecular adsorption,through Langmuir model to calculate the maximum adsorption capacity of CTAB-Chitosan@Al₂O₃to Methyl Orange,Congo Red and Reactive Blue,the maximum adsorption capacity were 327.87 mg/g,1250.00 mg/g and1017.90 mg/g.The study found that CTAB-Chitosan@Al₂O₃ can selectively adsorb anionic dye in the mixing system,especially in the mixing system of Basic Fuchsine and Reactive Blue,the selective adsorption capacity can be controlled by p H value.Electrostatic force and hydrogen bond force exited between the CTAB-Chitosan@Al₂O₃ and ionic dyes.It was electrostatic attraction for anionic dyes,and electrostatic repulsion for cationic dye.By adjusting the p H value can change the electrostatic repulsion between CTAB-Chitosan@Al₂O₃and cationic dye,when the electrostatic repulsion was smaller than hydrogen bond,CTAB-Chitosan@Al₂O₃ can adsorb the cationic dyes.