Preparation Of Amino-modified Nanocellulose And Adsorption Properties For Heavy Metal Ions

The rapid development of industry over the past few decades has led to increasing water pollution around the world.Adsorption method is widely used in the field of heavy metal wastewater treatment because of its advantages of simple operation and environmental friendliness.However,the traditional adsorbent materials have the disadvantages of high cost and complex post-treatment.Therefore,the preparation of a wide range of raw materials and green adsorption materials has become an urgent task.Nanocellulose is a nanometer-sized cellulose material of a certain size.Compared with other adsorbents,nanocellulose is a good material for heavy metal ion adsorbents because of its unique nanometer size and high specific surface area.Adsorption properties can be effectively improved by surface modification.Carboxylated nanocellulose(CNC)was synthesized from Eucalyptus Pulp by using ultrasonic assisted 2,2,6,6-tetramethylpiperidinyl-1-oxy radical(TEMPO)oxidation,then dialdehyde-based nanocellulose(DNC)was synthesized by sodium periodate oxidation.Finally,amino-terminated nanocellulose(ACNC)was obtained by amination with diethylenetriamine(DETA).The effect of DETA dosage on the content of N element on ACNC was investigated.The surface functional groups,surface morphology,thermal stability and element content of nanocellulose were characterized by FT-IR,TEM,TG and elemental analysis.FT-IR and elemental analysis indicated that the amino group was successfully grafted onto the nanocellulose chain;the size of ACNC in the TEM analysis was in the nanometer range;TG showed that the thermal stability of ACNC was improved by amination modification.The adsorption properties of ACNC on Pb(II),Cu(II)and Ni(II)showed that under the condition of room temperature,when the amount of ACNC was 0.1 g,the initial concentration of the solution was 400 mg/L and the p H was 5.0.After adsorption for 3 h,the adsorption amounts were 210.15 mg/g,139.42 mg/g and 131.27 mg/g,respectively.Adsorption behavior was consistent with pseudo second order kinetic model and Langmuir isotherm model,which indicates that the adsorption process is mainly chemical adsorption of single molecular layer.The amino-terminated hyperbranched polymer grafted dialdehyde-based cellulose nanocrystal material(HBPN-DNC)was prepared by amination modification of DNC with HBP-NH2.The effect of reaction conditions on the content of N element on HBPN-DNC was investigated.The surface functional groups,surface morphology,thermal stability and element content of nanocellulose were characterized by FT-IR,TEM,TG and elemental analysis.FT-IR and elemental analysis indicated that the amino group was successfully grafted onto the nanocellulose chain;the size of HBPN-DNC in the TEM analysis was in the nanometer range;TG showed that the thermal stability of HBPN-DNC was improved by amination modification.The adsorption properties of HBPN-DNC on Pb(II),Cu(II)and Ni(II)showed that under the condition of room temperature,when the amount of HBPN-DNC was 0.1 g,the initial concentration of the solution was 400 mg/L and the p H was 5.0.After adsorption for 3 h,the adsorption amounts were 248.33 mg/g,158.62 mg/g and 150.21 mg/g,respectively.Adsorption behavior was consistent with pseudo second order kinetic model and Langmuir isotherm model,which indicates that the adsorption process is mainly chemical adsorption of single molecular layer.