| With the development of industry,the pollution of heavy metals in water has become increasingly prominent.At the same time,the amount of waste corn stalks produced annually in our country is huge,nevertheless,the recycling rate is low,which continues to increase haze and pollution.In order to analyze the utilization of waste resources of pure environment-friendly raw material such as corn stalks,and at the same time provide a certain reference basis for the treatment of heavy metal ion wastewater,this project aims to use waste corn stalks,the biological resources to prepare magnetic nano-cellulose composite materials and discuss its effect on heavy metals in water.The adsorption performance of ions and the effect of desorption and reuse are expanding the research direction of heavy metal ion wastewater treatment and agricultural waste resource reuse.The results of the study are as follows:(1)Pretreatment of corn stalks by alkali solution combined with microwave method,microwave power of 320 W,microwave treatment time of 9 min,and the lowest crystallinity of43.18% and the lowest crystallinity index of 0.263 were obtained after three treatments.The corn stalks cellulose nanocrystals(CNC)are prepared by the sulfuric acid hydrolysis method,and the cellulose nanofibers(CNF)are prepared by the Tempo(2,2,6,6-tetramethylpiperidine oxide)oxidation method.The diameter of CNC is 20-40 nm,and the diameter of CNF is 50-70 nm.Both materials belong to nano-cellulose type I,and their thermal stability is lower than that of the original corn stalk cellulose,and they do not have magnetic properties.OCNC(Oxalic acid modified cellulose nanocrystals)and OCNF(Oxalic acid modified cellulose nanofibers)modified by oxalic acid are both nano-cellulose type I with carboxyl groups(-COOH)introduced on the surface.The crystallinity is compared with CNC and CNF has been improved.(2)Nano-Fe3O4 was prepared by the co-precipitation method,with an average particle size of 18.7 nm,which belongs to the inverse spinel type,and the maximum saturation magnetic intensity is 70.73 emu/g.Oleic acid modified nano-O-Fe3O4(Oleic acid modified Fe3O4)was prepared,with an average particle size of 16.5 nm,which still belongs to the inverse spinel type,and the maximum saturation magnetic intensity is 80.06 emu/g.The magnetic nano-cellulose composite material O-Fe3O4/OCNC(OCNF)was prepared by the method of liquid-solid phase composite.The crystal type has both the inverse spinel type and the cellulose type I,and the thermal decomposition temperature is higher than that of pure nano-cellulose.64.76 emu/g and59.74 emu/g are the maximum saturation magnetic intensity of the two composite materials,which greatly improves the magnetic response characteristics of nano-cellulose materials.(3)Taking Cr(VI)and Cu(Ⅱ)as the research object,using two composite materials O-Fe3O4/OCNC(OCNF)as the adsorption material,the best adsorption conditions for Cr(VI):the dosage of adsorption material is 0.45 respectively g/L and 0.35 g/L,the initial p H value is 1.0,the adsorption time is 60 min,the adsorption temperature is 60℃,and the initial concentration of Cr(VI)is 80 mg/L.The maximum adsorption capacity is 160.5 mg/g and 170.8 mg/g respectively;the best adsorption conditions for Cu(Ⅱ): the dosage of adsorption material is 0.5g/L and 0.6 g/L,the initial p H value is 5.5,the adsorption time is 80 min,The adsorption temperature is 45℃ and the initial concentration of Cu(Ⅱ)is 50 mg/L.The maximum adsorption capacities are 62.3 mg/g and 70.4 mg/g,respectively.The adsorption process conforms to the quasi-second-order kinetics and Langmuir model,and is mainly chemical adsorption,which belongs to monolayer adsorption.After adsorption,the composite material can easily achieve solid-liquid separation under the action of an external magnetic field,and the recycling rate is high. |
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