Study On Extraction Of Yellow Pigment From Hybrid Citrus Peel And Its Preparation And Application Of Skin Residue Modified Adsorbent

The hybrid citrus,also known as ugly orange,is currently one of the most popular fruits.The peel is largely discarded without reasonable utilization.How to improve its comprehensive utilization rate has become a research hotspot in recent years.In this study,hybrid citrus peel from agricultural and forestry wastes was used as raw material to extract natural pigments.The optimum extraction conditions were obtained through single factor experiments and response surface optimization,and the stability of yellow pigments from citrus peel was studied.The modified citrus peel biosorbent was prepared by chemical modification of the skin residue after the pigment extraction,and the optimal preparation conditions were determined.The modified product was characterized by infrared spectroscopy and scanning electron microscopy.The adsorption effect of modified mandarin peel on azo pigment,proanthocyanidin and hexavalent chromium ion was studied.The effects of pH value,temperature,time and solution concentration on the adsorption rate were investigated by static adsorption experiments.The adsorption mechanism was discussed by adsorption thermodynamics,adsorption kinetics and adsorption isotherms.(1)Anhydrous ethanol was selected as the extraction solvent.The optimal extraction conditions for the extraction of yellow citrus yellow by ultrasonic-assisted ethanol method were obtained by single factor and response surface optimization experiments:the optimal conditions were extraction time 30 min;ratio of material to liquid 1:12g/mL;power is 400W;temperature is 60?.The results of research on the stability of yellow peony residue showed that the yellow pigment of citrus peel was sensitive to indoor natural light,the light tolerance was not good,and it was suitable for preservation in the dark;the pigment was suitable for neutral weak base.It is stored under the condition;it is not affected by temperature,and its thermal stability is good;it is less affected by metal ions K+,Ca2+ and Mg2+;the common additive of food,NaCl,starch has no significant effect on the stability of yellow peony residue.(2)The citrus sorbent was prepared by epoxidation and amination.The nitrogen content was used as the index.Several important factors affecting the modification effect were investigated by single factor experiment.The best modification conditions were obtained:epoxidation reaction time.For 4h,the epoxidation reaction temperature was 50?.The amination reaction time was 5h and the amination reaction temperature was 60?.A new vibration peak was obtained at 2853cm-1 by infrared spectroscopy,which proved the success of the amination modification and gave it adsorption performance.Scanning electron microscopy(SEM)showed that the surface of the mandarin peel was significantly changed before and after modification.(3)The optimum pH value of the modified citrus peel to adsorb proanthocyanidins was 6;the optimum adsorption temperature was 40?;the optimum adsorption time was 90min.Adsorption thermodynamics studies show that the adsorption process is a spontaneous endothermic reaction and the adsorption efficiency of modified mangosteen on proanthocyanidins increases with increasing temperature.The fitting parameters of the adsorption kinetics model indicate that the adsorption process is more in line with the quasisecond-order kinetic equation,which proves that it is chemisorption.The adsorption isotherm fit is consistent with the Langmuir single molecule adsorption model.Cyclic adsorption experiments show that hydrochloric acid with a pH of 4 has a good analytical effect.(4)The optimal pH for the adsorption of azo-like pigments amaranth and tartrazine was 2;the optimum adsorption temperature was 50?;the optimal adsorption time for amaranth was 30min;the optimal adsorption for lemon yellow The time is 50min.Thermodynamic studies have shown that the adsorption process of the modified citrus peel on the azo pigment is a spontaneous endothermic reaction.The fitting parameters of the adsorption kinetics models of the two pigments are more in line with the quasi-second-order kinetic equation,indicating chemical adsorption.The adsorption isotherm indicates that the adsorption of azo pigments by modified mandarin citrus is more consistent with the Langmuir single molecule adsorption model.(5)The optimum pH value of the modified mandarin peel for Cr(?)adsorption is 3,the adsorption rate is 70.14%,the optimum adsorption temperature is 50?,and the optimum adsorption temperature is 50min.The adsorption thermodynamic parameters indicate that the adsorption process is a spontaneous endothermic reaction,and increasing the temperature facilitates the reaction.The fitting parameters of the adsorption kinetic model are more in line with the quasi-second-order kinetic equation,indicating that the adsorption process is chemisorption.The adsorption isotherm fit is consistent with the Langmuir single molecule adsorption model.