| With the development of industry,dyes have brought about more serious ecological pollution while bringing huge economic benefits.Dye wastewater is a major problem in industrial wastewater treatment because of its complex composition,difficulty in decolorization,high concentration of CODcr and BOD5,large changes in water quality and quantity,high suspended solids,and refractory components.Therefore,the current dye pollution control has drawn attention from all walks of life.Compared with other processes,the adsorption treatment of dye wastewater has the advantages of low cost,simple operation,no toxic and harmful substances,high efficiency and selective adsorption of certain compounds.The choice of adsorbent is the key to the treatment effect of adsorption.Chitosan and its derivatives are natural polymer materials with many sources,low cost,no toxicity,easy degradation,etc.,and contain chitosan molecules.A large number of active amino groups and hydroxyl groups can be modified under certain conditions to improve their adsorption performance and stability.The polyacryloyloxyethyltrimethylammonium chloride?DAC?monomer selected for graft modification has high cationic activity and charge density,and can be graft copolymerized with a monomer having other functional groups to introduce a quaternary ammonium salt group.At the same time,the subject uses magnetic separation technology,which greatly improves the reusability of the adsorbent.The major elements and conclusions are as below:?1?The synthesis of Fe3O4 nanoparticles by co-precipitation process and magnetic chitosan microspheres?MCPs?were prepared by emulsified cross-linking process;potassium persulfate?KPS?was used as initiator to initiate by free radicals.Polyacryloyloxyethyltrimethylammonium chloride?DAC?grafted magnetic chitosan microspheres?PMCPs?were prepared by branch copolymerization.?2?Characterization of MCPs and PMCPs,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,thermogravimetric analysis,particle size analysis,zeta potential,etc.indicate that DAC grafting is successful;X-ray diffraction pattern proves chitosan coating Grafting with DAC does not cause phase transformation of the crystal structure of Fe3O4 nanoparticles;hysteresis loop indicates that although the chitosan coating and DAC grafting will weaken the magnetic properties of Fe3O4,the magnetic particles can still be separated by an external magnetic field;?3?Using anionic dye Sunset Yellow?SY?as simulated wastewater,the effects of initial pH,initial concentration and adsorption time of dye wastewater on the adsorption of magnetic microspheres were studied,and desorption and regeneration experiments were carried out to explore the reusability of magnetic microspheres.The results showed that the adsorption capacity decreased significantly with the decrease of pH in the initial pH range of 2.010.0,and the adsorption capacity of PMCPs was significantly higher than that of MCPs.The adsorption capacity of PMCPs increased rapidly in the initial 60 min,and then the growth rate slowed down.The adsorption capacity does not change at all;when the initial concentration is low,the adsorption capacity of PMCPs increases significantly with the increase of dye concentration.After the concentration is greater than 900 mg/L,the growth rate slows down and finally reaches equilibrium;after 5 adsorption-desorption After the cycle experiment,PMCPs still have good adsorption properties.?4?adsorption model analysis showed that the adsorption of sunset yellow dye wastewater by magnetic microspheres PMCPs accorded with quasi-secondary adsorption kinetics?PSO?model and Langmuir adsorption isotherm model;at pH 2.0,temperature 25°C conditions The maximum adsorption capacity of PMCPs for sunset yellow dye wastewater is 787.14 mg/g;the adsorption of sunset yellow dye by PMCPs is spontaneous and exothermic.Compare PMCPs with other types of adsorbents that have been studied.The results show that the adsorption capacity of PMCPs is at a higher level. |
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