Amination Modification Of Apple Pomace Cellulose And Its Adsorption Properties For Bilirubin

In recent years,with the continuous expansion of the scale of concentrated apple juice production enterprises,the output of apple juice has continued to increase,and furthermore the output of apple pomace has also increased.It is usually used as feed,fertilizer or fuel,and even discarded,which makes a lot of apple pomace resources wasted.The high value utilization of apple pomace is the key to extending the apple industry chain.The total dietary fiber content in apple pomace is over 70%,of which water-insoluble dietary fiber accounts for more than 60%.Water-insoluble dietary fiber includes cellulose,hemicellulose,and lignin.And cellulose is the main component of water-insoluble dietary fiber.It can be modified to obtain materials with good functional properties,so as to realize the resource and high-value utilization of apple pomace,which is of great significance to the sustainable development of the apple industry.In this study,apple pomace cellulose was used as a basic raw material,which was aminated to obtain aminated apple pomace cellulose.Then,the apple pomace cellulose before and after the amination modification was characterized by structural characterization and surface morphology.Finally,the adsorption activity of bilirubin on apple pomace cellulose before and after amination modification was measured,and the influence of amination modification on cellulose adsorption activity was investigated.The main findings are as follows:(1)The orthogonal test results of the amination modification of apple pomace cellulose showed that the order of the influence of each factor on the increase of nitrogen in the amination modified apple pomace cellulose was as follows:ethylene diamine concentration>reaction time>reaction temperature>addition amount of NaHCO3.And the best process for the preparation of aminated apple pomace cellulose is:ethylenediamine concentration of 25%,reaction temperature of 75?,reaction time of 7.5 h,and NaHCO3 addition amount of 3.00 g.At this time,the increase of nitrogen in the product was 1.34%,and the yield of the product was 89.78%.The bulk density,filling density and hydration density of apple pomace cellulose after amination modification were reduced by 36.73%,23.53%,and 24.20%,respectively.After amination,the water holding capacity,oil holding capacity,and swelling capacity of apple pomace cellulose increased by 33.75%,1.69%,and 22.45%,respectively.(2)From the structural characterization results of apple pomace cellulose before and after modification,the characteristic absorption peaks of-NH2 appeared at 3167.68 cm-1,1119.38 cm-1,and 830.08 cm-1.The nuclear magnetic resonance analysis revealed that the substitution reaction site was the primary hydroxyl group on the cellulose glucose ring C6,and the two new peaks at ? of 57.50 ppm and 48.52 ppm were caused by the C linked to the amine group,which indicated that Amine groups were successfully introduced onto apple pomace cellulose.X-ray diffraction and nuclear magnetic resonance analysis found that the crystal type of unmodified apple pomace cellulose was typical cellulose type?,but the crystal type after amination modification was no longer typical cellulose type ?,and the crystallinity is reduced from 58.26%to 52.35%.From the scanning electron microscope analysis,it can be seen that the surface of the apple pomace cellulose after amination modification becomes rough,has obvious wrinkles,is uneven,and the structure is loose and porous.Thermogravimetric analysis results show that the thermal stability of apple pomace cellulose after amination modification is slightly reduced.(3)From the static adsorption kinetics curve,it can be known that the apple pomace cellulose after amination modification is more likely to form a stronger connection with bilirubin than the unmodified apple pomace cellulose.And after 2.5 h,the adsorption reached equilibrium,and the equilibrium adsorption amount was 6.52 mg/g.Scanning electron microscopy results showed that a large amount of bilirubin was attached to the surface of the aminated apple pomace after adsorption.This indicates that amination modification can significantly improve the adsorption capacity of apple pomace cellulose to bilirubin.From the analysis results of the influence of each single factor on the adsorption capacity,it can be known that when pH is about 7.4,the aminated apple pomace cellulose has the best bilirubin adsorption performance.With the increase of ionic strength,the adsorption of bilirubin by aminated apple pomace cellulose decreased significantly.The adsorption of bilirubin by aminated apple pomace cellulose is mainly physical adsorption.(4)Orthogonal test results on the adsorption of bilirubin by aminated apple dregs cellulose showed that the adsorption temperature was the most influential factor on the amount of bilirubin absorbed by aminated apple pomace cellulose.The optimum conditions for bilirubin adsorption by aminated apple pomace cellulose are:the adsorption temperature is 37?,the adsorption time is 3.0 h,the added amount of aminated apple pomace cellulose is 0.15 g,and the bilirubin solution concentration is 0.30 g/L.At this time,the amount of bilirubin adsorbed by aminated apple pomace cellulose was 9.75 mg/g.And from the analysis of the adsorption isothermal curve of aminated apple pomace cellulose to bilirubin,it can be known that the adsorption rule of bilirubin in solution by aminated apple pomace cellulose accords with Freundlich equation.