Study On The Extraction Of Hydroxyapatite And Collagen In Ionic Liquid From Crucian Carp Scales

Tens of thousands of tons of fish scales are produced in the process of fish processing in China.These scales are rich in hydroxyapatite(HA)and collagen.Extraction of HA and collagen from fish scales can reduce environmental pollution and increase the added value of fish.In addition,the extracted HA and collagen can be used in food,biomedicine,electrochemistry,cosmetics and many other fields.Four ionic liquids,choline chloride/1,4-butanediol,choline chloride/glycerol,choline chloride/triglycol and choline chloride/ethylene glycol,were prepared in this paper.The experimental data showed that the above four ionic liquids,1-allyl-3-methylimidazole chloride ionic liquids and 1-ethyl-3-methylimidazole bromide ionic liquids had different effects on the extraction of HA from Crucian Carp scales.Ionic liquids are selected based on experimental data.The effects of time,temperature and solid-liquid ratio on the extraction of HA and collagen from Crucian Carp scales with choline chloride/1,4-butanediol were investigated.On the basis of single factor,orthogonal test and verification test were carried out,and the best extraction conditions were determined.The extracted HA and collagen were characterized by Fourier transform infrared spectroscopy,ultraviolet spectroscopy,scanning electron microscopy,thermogravimetry,differential scanning calorimetry,X-ray diffraction and particle size analysis.Ionic liquids were recovered and characterized.At last,the adsorption of HA on Agilent standard solution was studied.The HA before and after adsorption was characterized by Fourier transform infrared spectroscopy and X ray spectroscopy.The results showed that there was no significant difference between the two imidazole ionic liquids and choline chloride/1,4-butanediol in the extraction of HA.Choline chloride/1,4-butanediol was selected to extract hydroxyapatite and collagen from Crucian Carp scale in terms of safety and cost.The optimum extraction conditions were:70?,2.5 h and solid-liquid ratio of 1:15.The yield of HA and collagen was 40.58%and 4.14%respectively.The extracted HA is hydroxyapatite containing carbonate with irregular morphology and uneven particle size.The extracted collagen maintains a complete three helix structure.By the recovery and reuse of choline chloride/1,4-butanediol,the results shows that the structure of ionic liquids did not change before and after recovery.The yields of HA and collagen extracted from recovered ionic liquids were 41.60%and 5.03%respectively.HA was used to adsorb metal ions and to characterize HA before and after adsorption,the results shows that HA can adsorb metal ions,such as,Pb,Cu,Zn and Ag.