Preparation Of Ammonia Group Modified Chitosan And Nano Fe₃O₄ Composite Material And Its Adsorption Performance For Heavy Metal Ions

Water is the source of life and the most important substance among the six types of nutrients that sustain human survival.At present,our country is facing the dilemma of resource-related water shortage in the north,water-quality shortage in the south,and engineering water shortage in the central and western regions.Once water is polluted,it will have an adverse effect on the human body and the environment.Heavy metal pollution is a type of water pollution.Under a certain concentration,heavy metals not only have carcinogenic effects,but also can cause various diseases and affect human reproduction and nervous system.Therefore,the treatment of heavy metal pollution is of great significance in real life.At present,sewage treatment technologies such as adsorption,chemical precipitation,ion exchange,membrane filtration,bioremediation,ion exchange,catalysis,reverse osmosis,and electrochemical treatment have been extensively studied by researchers.Among them,the adsorption method is highly efficient,environmentally friendly,and easy to operate.These advantages make it the most commonly used sewage treatment technology.Chitosan is the only basic polysaccharide among natural polysaccharides.It has a large number of hydroxyl and amino groups that can be used to coordinate metal ions.It is a natural metal ion adsorbent.However,chitosan is soluble in weak acid and is easily degraded under acidic conditions,has poor mechanical properties,and is difficult to achieve recovery after adsorption,which limits its application.The modification can not only make the physical and chemical properties of the chitosan material more stable,but also increase the number of nucleophilic functional groups,thereby enhancing the ability to bind metal ions and achieving the effect of improving the adsorption performance.The composite material of modified chitosan and ferroferric oxide can simultaneously obtain ideal adsorption and separation effects.In this paper,a series of ammonia-based group-modified chitosan and ferroferric oxide composite materials were prepared,and the adsorption performance of heavy metal ions was studied systematically.Results are as follows.(1)Firstly,tetraethylenepentamine-modified chitosan(TEPA-CS)was prepared with epichlorohydrin as the crosslinking agent,and then compounded with diamond-shaped nano-iron tetroxide to prepare a composite material(TEPA-CS/d-Fe₃O₄).The adsorption of Cu²⁺was systematically studied.Under the conditions of T=298 K,p H=5.5,t=30 min,and C₀=250 mg·L^-1,its maximum adsorption capacity for Cu²⁺was 52.69 mg·g^-1.The experimental data fit well with Langmuir isotherm model and pseudo second order kinetic model.After five cycles of repeated use,the adsorption capacity for Cu²⁺is 72.22%of the first adsorption capacity.(2)Using epichlorohydrin as the crosslinking agent,triethylenetetramine(TETA),tetraethylenepentamine(TEPA),polyethylene polyamine(PEPA)modified chitosan and spherical nano ferroferric oxide composite materials(TETA-CS/s-Fe₃O₄,TEPA-CS/s-Fe₃O₄,PEPA-CS/s-Fe₃O₄)were prepared.The effect of ammonia group numbers in the modifier on the adsorption of Cu²⁺by the composite was systematically studied.Langmuir model and pseudo second-order kinetic model were used to fit the adsorption capacity of the three materials.The retention rates of adsorption capacity were 82.02%,81.42%and 77.60%respectively after five times of reuse.(3)The adsorption performance of Pb²⁺and Ni²⁺on the composite material of tetraethylenepentamine modified chitosan and spherical nano ferroferric oxide TEPA-CS/s-Fe₃O₄ was systematically studied.The results show that at T=298 K,p H=5.5,t=1.5 h,C₀=200 mg·L^-1,when the dosage is 10 mg/25 m L,the maximum adsorption capacity for Pb²⁺and Ni²⁺are 382.53 and 66.95 mg·g^-1,respectively.The adsorption data of the two heavy metal ions are in accordance with the Langmuir isotherm model and pseudo second-order kinetic model.The retention rates of adsorption capacity were 92.90%and 87.10%,respectively.