Study Of Adsorption Organic Dyes By Surface Magnetic Carbon Nanotubes

The pollution caused by organic chemicals to water bodies is one of the ecological and environmental problems that cannot be ignored.Organic dye is a kind of organic pollutant that causes changes in the color of water and deterioration of aquatic environment.Due to the demand for dyeing in textile,printing and dyeing,paper-making,plastics,leather,cosmetics,pharmaceuticals and other industries,more than 10,000 kinds of dyes and pigments are used and produced worldwide every year.10-15%of the dyes will be discharged into natural water due to improper treatment,and about 50,000 tons of dyes will be discharged into the environment every year.How to adopt effective terminal treatment technology to control the pollution of organic dyes to water bodies while strengthening the control of pollution sources is also a problem worthy of further exploration in the field of ecological environment protection.The development of nanotechnology has not only promoted the rapid development of optoelectronic materials manufacturing,communication,medical diagnosis and other fields,but also provided a new opportunity for the development of eco-environmental technology.In view of the problem of organic dyes on water pollution and aiming to synthesize new magnetic nano-adsorbents with large adsorption capacity and easy material recovery,this paper adopted carbon nanotubes（CNTs）as substrates and prepared three kinds of magnetic nano-adsorbents according to the idea to modify and functionalize carbon nanotubes by different biodegradable organic polymers and further load it with magnetic nano-iron tetroxide materials,and analyzed the adsorption properties and regeneration properties of the prepared materials through the conditions optimization and model construction of adsorption by means of removing two widely used cationic organic dyes（methylene blue,basic fuchsin）and one anionic organic dye（Congo red）,and taking its adsorption capacity and removal efficiency as key considerations.The detailed results are shown as follows:（1）A polyaspartic acid modified magnetic carbon nanotubes adsorbent was prepared by using carbon nanotubes as substrate material and polyaspartic acid as surface functional modifier by modifying polyaspartic acid on the surface of carbon nanotubes through chemical cross-linking method,and loading Fe₃O₄ on the surface of carbon nanotubes by chemical coprecipitation method.Furthermore,the methylene blue was selected as the removal target.The prepared adsorbent can absorb the methylene blue in the solution with pH of 8.0 within 20 minutes under room temperature through the optimization of adsorption conditions,adsorption kinetics and adsorption isotherm model construction.The maximum adsorption capacity of methylene blue is 116.28 mg g^-1,which is better than conventional adsorbents,and can be regenerated by ethanol under acidic conditions due to good regeneration performance.（2）A magnetic carbon nanoadsorbent modified by sodium alginate was prepared by chemical crosslinking and coprecipitation with carbon nanotubes as the substrate and sodium alginate as the modifier.The prepared adsorbent has good adsorption performance for basic fuchsin,and the optimum adsorption conditions are as follows:T=25℃,pH=8.5,t=20 min,and the maximum adsorption capacity for basic fuchsin is 625 mg g^-1.Besides,the adsorption kinetics and isothermal process can be described by pseudo-second-order kinetic model and Langmuir model,and the adsorption can be regenerated by acid ethanol（0.1 M dilute hydrochloric acid:anhydrous ethanol=1:4）.（3）Based on the unique properties of dendritic macromolecular structure and rich functional groups,a dendritic organic polymer polyamidoamine branch was used as a modifier to modify carbon nanotubes to synthesize a magnetic nano adsorbent modified by polyamidoamine.Combining with strong positive charge characteristics of polyamide amine,the adsorption properties of adsorbent for Congo red were investigated by using it as the removal object.The optimal adsorption conditions are as follows:T=25℃,pH=5.0,t=40 min,and the maximum of adsorption capacity of Congo Red is 178.57 mg g^-1.The adsorption capacity is obviously better than that of conventional adsorbents.Three kinds of magnetic carbon nano-adsorbents has been successfully prepared in this paper with good adsorption performance and environmental friendliness,and the adsorbent prepared can be applied to remove organic dyes methylene blue,basic fuchsin and Congo red in wastewater.Moreover,the prepared adsorbents and optimized adsorption conditions provide some basic materials and technical support for the terminal purification of methylene blue,basic fuchsin and Congo red in wastewater,and the results also provide some ideas for the preparation of carbon nanotube-based adsorbents.