Preparation Of Magnetic Macroporous Resin And Studies Of Absorption Properties For Apple Polyphenols

Apple pomace was the solid waste in the production of apple juice and wine,which was rich in extractive polyphenols.The content of polyphenols in apple pomace was much higher than that in pulp.Apple polyphenols had many functional activities,such as antioxidation,anticancer,anticarious,antiallergic,inhibition the growth of microbes,etc.So apple polyphenols were paid more and more attentions and became a research focus for scholars both domestic and abroad.So turning waste into wealth and extraction and separation of apple polyphenols had very big potential value and economic interests.In this paper,the initial preparation and use of magnetic macroporous resin for adsorption and separation of polyphenols in apple pomace was discussed.The magnetic macroporous resin was characterized.The adsorption condition was optimized,and the best adsorption process was determined.Kinetics and thermodynamics of the adsorption process were conducted.And the desorption of apple polyphenols from magnetic macroporous resin was discussed.The aim of this paper was to provide a new way for extraction and separation of apple polyphenols and establish theoretical basis for extraction process of apple polyphenols by magnetic macroporous resin.The results of this study were as follows:1.Hydrophilic Fe3O4 particles were synthesized by coprecipitation method and the surface modification with oleic acid was poformed,which turned hydrophilic Fe3O4 into lipophilic Fe3O4.Magnetic macroporous resins were prepared through micro-suspension polymerization.Fe3O4 particles and magnetic macroporous resins were characterized by scanning electron microscopy,laser particle size analyzer,and Superconducting quantum interference magnetic measurement system.Fe3O4 particles was nanometer level,there was agglomerative phenomenon in solution,with poor dispersivity and irregular shape,super paramagnetic.Fe3O4 modified with oleic acid had better dispersivity than Fe3O4 particles,super paramagnetic.The magnetic macroporous resins were micron,spherical,with uniform particle size,good dispersion and rough surface,super paramagnetic.2.The absorption and desorption properties and reuse cycles between magnetic macroporous resins and normal resins were compared.Results:Of the five kinds of normal resins(D3520,D280,D4020,AB-8,H103),the AB-8 resin had the best absorption and desorption properties;magnetic macroporous resins had better absorption efficiencies and desorption efficiencies than AB-8 resins.After reusing 4 times,the adsorption of magnetic macroporous resins was still higher than 70%,had better stability than AB-8 resins.3.The single-factor experiment and response surface method was applied to optimize the adsorption factors of apple polyphenols by magnetic macroporous resins.Process parameters had significant effect on adsorption rate of apple polyphenols.The optimum adsorption conditions of apple polyphenols by magnetic macroporous resins were as follows:usage of magnetic macroporous resins 0.12 g/mL,adsorption temperature 30.4 ?,pH 4.0,and under this condition,the adsorption rate could reach to 94.03%.4.The pseudo-first-order kinetics model,the pseudo-second-order kinetics model,Elovich equation and pore diffusion equation were used to fit the adsorption kinetics process.Three isothermal adsorption models(Langmuir,Freundlich and Temkin)were used to analyse adsorption thermodynamics properties.The results showed that adsorption kinetics process conformed to the pseudo-second-order kinetics model.At higher temperature the magnetic macroporous resins had a high adsorption capacity.Adsorption thermodynamics conformed to Freundlich isothermal adsorption model.The results of thermodynamic parameters were?G<0,?S>0,which indicated that adsorption of apple polyphenols onto magnetic macroporous resins was a spontaneous process along with entropy increase.During the adsorption process,with polyphenols concentration increasing,?H<0,which showed that the adsorption reaction is exothermic process,lower temperature is advantageous to the reaction.5.The desorption research was conducted using ethanol solution with three process parameters:desorption time,temperature and ethanol concentration.Results:desorption rate increased with the extension of time,the desorption equilibrium appeared at the third hour;desorption rate is slightly lower at 20 ?,and increased with temperature increasing;with the increase of ethanol concentration,desorption rate increased and then decreased.Under the condition of elution time 3 h,elution temperature 30 ?,ethanol volume fraction 70%,the desorption rate could reach to as high as 96.17%.