Study On The Removal Method Of PAEs In Evening Primrose Oil

Phthalatic acid esters(PAEs)are environmental hormones with reproductive and genetic toxicity to the human body.Due to their fat-soluble properties,PAEs have been commonly reported in edible vegetable oils.Among them,DBP and DEHP are the two most common types of PAEs pollutants.In order to control the content of PAEs in edible oils and reduce the exposure risk of PAEs to the human body,the state administration of market supervision and administration clearly stipulated in the standard[2019]no.214 document issued that the maximum residues of DEHP,DINP and DBP in oil and fat foods are 1.5 mg/kg,9 mg/kg,and 0.3 mg/kg,respectively.This article aims to remove two common PAEs(DBP and DEHP)in evening primrose oil.In this study,an activated clay with a strong ability to remove two PAEs in evening primrose oil was prepared,and the characterization structure,optimal adsorption process conditions,adsorption mechanism and regeneration effect of the CTAB/chitosan-clay composite were carried out,and the quality indexes of evening primrose oil treated by CTAB/chitosan-clay composite were measured.The main conclusions are as follows:(1)In this paper,chitosan and CTAB were used to modify activated clay,and the optimal ratios of chitosan:CTAB:activated clay were determined to be 0.2:0.3:1.Compared with pristine activated clay(5.95±1.04%)and chitosan(6.61±0.28%),CTAB/chitosan-clay composite(16.73±0.44%)had a higher removal efficiency for DBP in evening primrose oil.The SEM,XRD,BET and FT-IR characterization experiment results of the CTAB/chitosan-clay composite showed that the modification did not destroy the basic structure of the activated clay,and the surface morphology of the CTAB/chitosan-clay composite was rougher,which meant possibly exposing more functional groups.Futhermore,the specific surface area of the CTAB/chitosan-clay composite decreased from 137.0916 m~2/g to 18.4283 m~2/g,and the average pore diameter increased from 6.6768 nm to 15.9528 nm.Meanwhile,CTAB/chitosan-clay composite had a larger interlayer spacing.(2)Through single factor and response surface optimization experiments,the best process conditions for the adsorption of PAEs in evening primrose oil by CTAB/chitosan-clay composite were determined:under vacuum conditions,adsorption time 43 min,adsorption temperature 85℃,adsorbent addition amount10%,DBP and DEHP removal rates of DBP and DEHP could reach 28.84±1.63%and23.37±2.18%,respectively.Compared with pristine activated clay,the removal rates of DBP and DEHP were increased by 2.39 times and 1.36 times,respectively.After adsorption treatment of CTAB/chitosan-clay composite,evening primrose oil also had a good quality,and there were no significant change in acid value,iodine value,peroxide value,p-anisidine value and fatty acid composition.Lovibond color was Y30R2.0.However,the total amount of phytosterols was reduced by 3.9%.The results of the adsorption kinetic curves and the adsorption isotherm models showed that the adsorption of PAEs by the CTAB/chitosan-clay composite conformed to the quasi-second-order kinetic model and the Freundlich adsorption isotherm model,respectively.The value of n(n>1)and the R_L(between 0 and 1)indicated that the adsorption process was preferential adsorption.Adsorption was dominated by monolayer adsorption,including physical adsorption and chemical adsorption.There might be interactions between functional groups,hydrogen bonding forces,electrostatic forces,and dispersion forces.(3)Using ultrasonic-assisted organic solvents to desorb and regenerate waste clay,and the optimal regeneration conditions of waste clay were determined as ultrasonic power 200 W,regeneration temperature 25℃,regeneration time 25 min,solid-liquid ratio 1:4,regenerated once,the removal rate of PAEs could reach 15.86%.Although the adsorption capacity of regenerated clay for PAEs was significantly lower than that of fresh CTAB/chitosan-clay composite,it was still stronger than that of ordinary activated clay used for the first time.The adsorption capacity of reclaimed clay had dropped sharply with the increase in the number of recycling cycles.Therefore,it was recommended that the waste clay be recycled only once.