Research On The Preparation Of Manganese Ferrite/Chitosan And Its Adsorption Properties Of Heavy Metals

With the development of social economy,the pollution in the water environment gradually increases,which has a certain effect on the environment and human health.Especially with the mining,chemical industry and leather manufacturing（containing chromium,cadmium,copper,mercury,nickel,zinc and other heavy metal ions）development,if the waste disposal way is unreasonable,can cause a variety of heavy metals into the water.The heavy metals in the water are transferred from the water phase to the solid phase in the sediment of the rivers and lakes under the action of physical precipitation and chemical adsorption,and the sediment becomes the"sink"of heavy metal.However,with the change of the external environment conditions,the sediment can release heavy metal to the water body again,and there is obvious secondary pollution,and the sediment becomes the"source"of heavy metal.Therefore,the heavy metal pollution in water and sediment has become an environmental concern in the world.And how to scientifically and rationally repair the water and sediment of heavy metal pollution has become one of the hot spots.In this experiment,we first prepared the magnetic material ferrite manganese and coated ferric acid manganese with chitosan to prepare the new magnetic ferric ferric acid manganese/chitosan adsorbent.Through single factor experiment explores the chitosan concentration,acid manganese iron and the quality of the ratio,the concentration of glutaraldehyde crosslinking agent,pH and reaction temperature on the reaction solution of magnetic iron manganese acid/chitosan adsorption performance influence.When the concentration of chitosan was 10mg/L,the adsorbent of ferric acid manganese/chitosan was a good microsphere,without the phenomenon of tailing.Iron manganese acid and chitosan mass ratio is 0.2:1,the Cu（Ⅱ）adsorption quantity of 72.38 mg/g,increase with the ratio of acid manganese iron,manganese ion and iron ion and chitosan amino and hydroxyl form hydrogen bonds increase,thus occupies the"active-site"that could not be adsorbed copper ions.Glutaraldehyde concentration was 25%,the Cu（Ⅱ）adsorption capacity up to 63.45mg/g,chitosan linear long chain into a mesh by two-dimensional structure,mechanical strength increased.When the pH was 12,the adsorption capacity of Cu was 64.29mg/g.In addition to increasing pH,the adsorption capacity is basically no longer increased.When the reaction temperature was 40,the maximum adsorption capacity of Cu was 70.08mg/g,and the temperature adsorption capacity decreased.Through orthogonal experiment the comprehensive investigation of chitosan concentration,amount of manganese ferrite,the concentration of glutaraldehyde and naoh concentration on the influence of the magnetic chitosan composite,optimizing the parameters of the preparation of magnetic chitosan microspheres.The optimal parameter was the concentration of chitosan at 10mg/L,m（MnFe₂O₄）/m（CS）=0.2:1,the mass fraction of glutaraldehyde was 30%,the reaction temperature was 45℃,the reaction pH was 12,and the reaction time was 12h.The saturation magnetization intensity of magnetic ferric ferrite and chitosan by magnetic hysteresis is12emu/g,and the residual magnetism and coercivity are not observed,which indicates the properties of superparamagnetism.Settlement by magnetic fields,the iron manganese acid/chitosan can be done in the 20s,and to free settling is 100s.New preparation of manganese iron acid/chitosan adsorbent has good magnetic performance,which can realize quick solid-liquid separation.Through the adsorption experiment,the initial concentration,temperature and time of the pH and heavy metals were studied systematically,and the adsorption performance of the magnetic ferrite manganese/chitosan adsorbed heavy metal copper and cadmium was investigated.The best adsorption conditions of Cu²⁺in the water body are at pH=5,the temperature is 25℃,and the adsorption time is 62.3mg/g in 15 minutes.Best adsorption of Cd²⁺condition is in the pH=7,the temperature is 25℃,the adsorption time for 15 minutes under the maximum adsorption capacity of 60.6 mg/g.According to the thermodynamic study,both Cu²⁺and Cd²⁺in the adsorption water of manganese ferric acid manganese/chitosan were consistent with the Langmuir model,which was mainly single molecular layer adsorption.The adsorption reaction is spontaneous and is an exothermic process.The kinetics study shows that the adsorption process conforms to the quasi-second-order kinetics model,that is,chemical adsorption is the most important step to control the adsorption rate.Through the regeneration experiment,it was found that the adsorption capacity of manganese/chitosan in the first three cycles was still above 35mg/g.By analyzing the pollution sediment content of copper and cadmium metal found that adding iron manganese acid/chitosan adsorbent 7 days later,the heavy metal cadmium concentration by4.35 mg/kg to 0.8 mg/kg,the mass concentration of heavy metal copper from 335.70 mg/kg decreased to 82.42 mg/kg.By heavy metals BCR extraction experiment results show that sediment in Cd,Cu can be extracted and acid can also square one content reduce,the most obvious weak acid extraction of cadmium metal state by 0.43 mg/kg decreased to 0.04 mg/kg,but also the types of 2.26 mg/kg decreased to 0.1 mg/kg,the weak acid extraction condition of copper from 73.7mg/kg decreased to 6.24 mg/kg,but also the types of 113.36 mg/kg decreased to 9.74 mg/kg,effectively reduce the harm of heavy metals on the surrounding environment.