Sericin Recovery From Alkaline Degumming Wastewater By Electrochemical Technology

Sericin,a water-soluble globular protein wrapped the silk strands,has the wide applications in the area of the cosmetic,clinical medicine,biomaterials and finishing on the health care textile.But the organic wastewater containing the highly concentrated sericin is usually discharged into the river by most of domestic factory.And thus,it will become the serious pollution to the ecological system.Therefore,it is very critical to develop the techniques to recover the sericin from the silk degumming wastewater.The main methods of sericin recovery from the wastewater based on the chemical and physical principles are summarized,which include the acidic precipitation,organic solvent precipitation,chemical coagulation,ion exchange method,centrifugation,freeze-method and ultrafiltration method.A novel,environmental and simple method based on our current research is also proposed which named electrochemical method.The principle of recycling sericin by this method is:Sericin protein has the nature of the colloidal particles with the isoelectric point about 3.8-4.5.Degumming of silk fiber is usually in alkaline condition.The pH of the degumming wastewater is above the PI,so the sericin protein in the wastewater charges negative.According to the electrical properties of sericin protein,we apply the electric field to the wastewater containing sericin.As a result,the sericin protein with charges will move directionally and gather gradually.The experimental study on recycling sericin by electrical method was shown in chapter 3.UV-Vis spectrophotometer was used to establish the linear relationship between absorbency of solution and its concentration.It discussed the influence of the electrode materials,current density,reaction time and electrode spacing on the extraction efficiency of sericin.The results showed that the anode graphite rods as reaction materials,in the current density of 2 mA/cm2,the reaction time of 120 min,electrode spacing in 3 cm,sericin extracted efficiency can reach about 60%.In chapter 4,the untreated sericin solution and sericin precipitation extracted by electrical method were processed with vacuum freeze drying.The sericin secondary changes after applying to the electric field were discussed by infrared spectroscopy(FTIR),circular dichroism(CD),X-ray diffraction(XRD)measurement.The analysis showed that the secondary structure of sericin changed from random coil to ?-sheet trend after applying the electric field to the sericin solution.The sericin powders obtained from this method have been characterized in terms of dissolution ratio,molecular weight distribution and amino acid analysis.The results showed that the molecular increased,the content of hydrophobic amino acid increased and the dissolution rate decreased.