Design And Synthesis Of High-effective Adsorbents For Patulin Removal And Performance Evaluation

Patulin(PAT)is one of the most common mycotoxin that frequently found in numerous fruits and fruit products.Apple juice with PAT contamination causes severe food issue which has attracted wide attention throughout the world.The level of PAT in apple juice is not only considered as a crucial indicator for juice quality and safety,but also a trade barrier of the domestic apple juice export.Therefore,the control of PAT contamination in apple juice is of great importance to the development of apple industry and break the trade bottleneck of domestic apple juice export.Adsorption,as one of the most effective process,has been widely used in practical to remove PAT due to the properties of convenient operation.Traditional methods usually used activated carbon and microporous resin as the adsorbents.But their application was limited due to the drawback of the inferior adsorption capacity and tedious separation steps.In order to solve the above problem and meet the special requirements for adsorbent in practical application,herein,three adsorbents with diverse features have been designed and synthesized,their feasibility of removing PAT from apple juice was comprehensively evaluated though the systematic adsorption experiment and toxicity tests in vitro and in vivo.The main research content and results are as follows:(1)Design and synthesis of surface functionalized Ui O-66(NH₂)nano-adsorbent and study on its adsorption behavior toward PAT.With the aim of increase the functional groups of adsorbent for improving PAT adsorption capacity,a nano-adsorbent,Ui O-66(NH₂)@Au-Cys,was synthesis using Ui O-66(NH₂)with excellent stability as the substrate for cystine(Cys)modification.Characterization results illustrated that a large amount of PAT binding sites,such as-COOH,-NH₂ and-OH,was introduced to the surface of the nano-adsorbent.Series adsorption studies of kinetic,isotherm and thermodynamic were conducted to reveal its adsorption behavior for PAT,the results showed that adsorption process was spontaneous and endothermic,which could be well described by the Pseudo-second order model and Freundlich isotherm model.The maximum adsorption capacity obtained from theroretical calculation was4.38?g/mg,which was 10 times higher than the microbe-based biosorbents.The adsorption time was shortened simultaneously from 20 h to 3.5 h.(2)Study on the PAT adsorption behavior of the micro-sized adsorbent from the surface engineering of diatomite.For the purpose to overcome the difficulty of separation of nano-adsorbent,diatomite,the juice filter aid,was selected as the micro-sized bulk to fabricate the GO-SH/diatomite via wrapping sulfur-functionalized graphene oxide(GO-SH)nanosheets on the surface of diatomite,in which GO-SH nanosheets can donate abundant active sites to improve the PAT adsorption capacity of traditional diatomite and diatomite severed as support substrate to facilitate the separation of the adsorbent.Comprehensive characterization showed that the combination between GO-SH and diatomite was stable and abundant-COOH,-OH and-SH was gifted to the surface of GO-SH/diatomite.Systematic adsorption kinetic and thermodynamics experiments and model fitting revealed that the PAT adsorption process for GO-SH/diatomite was spontaneous and endothermic.Pseudo-second order model and Freundlich isotherm model could be used to depict the process.The theoretical maximum adsorption capacity of GO-SH/diatomite for PAT was 10.68?g/mg.Compared to the previous reported adsorbent,the PAT adsorption capacity of GO-SH/diatomite was not only significantly higher than microbial adsorbents and traditional activated carbon,but also 2-10times superior to the typical thiol-functionalized adsorbent.(3)Design and synthesis of the composite aerogel with GO-SH doping and study on its PAT adsorption behavior.For the view of simplify the separation step of the powdery adsorbent and further improve the operability and adsorption performance of adsorbent,GO-SH doped aerogel was prepared by optimizing the loading mass of GO-SH in the carrier which was formed by the chemical cross-linking of carboxymethyl cellulose(CMC)and polyethyleneimine(PEI).Consecutive characterization revealed that the aerogel doped with0.04%GO-SH exhibited excellent mechanical stability and adsorption capacity.GO-SH wrapped on the surface of its fiber skeleton,which not only benefit to PAT adsorption by GO-SH,but also convenient for separation of the composite aerogel.Adsorption kinetic and thermodynamics test demonstrated that the GO-SH was benefit for enhancing the affinity between the aerogel and PAT,which resulted in the improvement of adsorption capacity.The adsorption kinetics of the aerogel toward PAT was well-fitted by the pseudo-second order model,and this spontaneous endothermic process was consistent with the Langmuir isotherm model,its theoretical maximum adsorption capacity of PAT was 24.75?g/mg,which was 2.5and 5 times higher than GO-SH/diatomite and Ui O-66(NH₂)@Au-Cys,respectively.(4)The feasibility evaluation of the adsorbents used in apple juice.The PAT removal efficiency,the level of residual adsorbent and changes in juice quality were investigated to assess the applicability of PAT removal from apple juice by Ui O-66(NH₂)@Au-Cys,GO-SH/diatomite and GO-SH doped aerogel,respectively.The results showed that Ui O-66(NH₂)@Au-Cys,GO-SH/diatomite and GO-SH doped aerogel could remove 87%,90%and89%PAT in apple juice within 5 h,respectively.After finishing the adsorption of the three adsorbents,the content of PAT in apple juice was below the maximum permitted level recommended by national standard.There were no residual GO-SH/diatomite and GO-SH doped aerogel in apple juice due to their fascinating properties of excellent stability,large particle for easy separation,while the residual level of nano-sized Ui O-66(NH₂)@Au-Cys was0.12?g/m L since it could not be completely separated.Moreover,the adsorption process of the three adsorbents did not cause significant deterioration in crucial quality parameters of apple juice.(5)Safety evaluation of the adsorbents.The toxic effect of Ui O-66(NH₂)@Au-Cys,GO-SH/diatomite and GO-SH doped aerogel were comprehensively investigated in vitro and in vivo to evaluate their cytotoxicity and acute toxicity.Results showed that the recommended dosage of the adsorbents used in apple juice did not caused cytotoxicity and the cell viability was higher than 90%.Furthermore,acute toxicity test on mice suggested that both of Ui O-66(NH₂)@Au-Cys,GO-SH/diatomite and GO-SH doped aerogel had not adverse effect on the body weight,blood biochemical indices and histopathology of major organs even the dosage used for acute toxicity test was 500 times higher than the recommended dosage which were added in apple juice.In conclusion,the above results indicated that Ui O-66(NH₂)@Au-Cys,GO-SH/diatomite and GO-SH doped aerogel exhibited excellent PAT adsorption performance and safety that can to be used in apple juice.The three types of adsorbents designed in this paper not only support various options for efficient removal of PAT from apple juice,but also provide new ideas and reference for the PAT adsorbent design in the future.