Sericin Protein Immobilization And Its Effect On The Adsorption Of Heavy Metal

In recent years,China’s economic development is rapidly,the country’s key industries involving heavy metals continued to increase production capacity,heavy metal pollutant emissions are growing.Various chemical forms of heavy metals exist in the environment,can not be biologically degraded,but into the food chain of the ecosystem in precipitation,enrichment,migration,caused serious harm to human society and the natural environment.Therefore,the pollutants removal of heavy metals in environmental media become an important topic in the field of environme-ntal science.Fiber or resin material for heavy metal chelating selective function was currently the most research value of the adsorbent.However,due to the preparation process was too complicated,high cost,the practical application was less.This paper based on a natural protein,make water-soluble proteins become adsorbent with chelating functions.And explored their adsorption behavior of aqueous solutions of cadmium,antimony contaminants,examining their potential in practical application.The sericin was immobilized by the embedding,embedding-crosslinking,crosslinking-embedding,adsorption-crosslinking and crosslinking-adsorption methods,repectively,with chitosan or sodium alginate as carrier.With the aim to removal heavy metal cadmium and antimony,different immobilization methods on the adsorption of heavy metals was studied to select the best immobilization carreiers and methods under the experimental conditions.On this basis,the adsorption conditions of immobilized sericin remove the heavy metal ions in the wastewater,and the immobilization of sericin adsorptive capacity and mechanism of heavy metals was discussed.The main conclusions are as follows:1.With chitosan as the carrier,glutaraldehyde as crosslinking agent,using embedding-crosslinking of sericin protein immobilization to obtain spherical solid adsorbent.Through static adsorption experiments found that when chitosan concentration was 30 g/L,the volume fraction of 1%glutaraldehyde,Cocoon wastewater and chitosan solution volume ratio of 1:1,the spherical solid adsorbent prepared for heavy metals adsorption maximum cadmium and antimony,respectively 102.72 mg/g and 99.42 mg/g.2.Adsorption of heavy metals was studied for the immobilized sericin protein,mainly studies the pH,temperature and time on the absorption performance of the immobilized sericin.The results showed that:Under optimum conditions,the use of Langmuir and Freundlich models to simulate,it was concluded that the Freundlich equation better describe the adsorption behavior of immobilized sericin to Cd2+.The adsorption process is an endothermic process and more in line with second-order kinetic model.At a pH of 7,the temperature was 30℃,the reaction time was 120 min under conditions of immobilization sericin of Cd2+ adsorption equilibrium,adsorption equilibrium amount of 109.94 mg/g.Langmuir equation better described the immobilized sericin of Sb3+ adsorption behavior,the adsorption process is an endothermic process and more in line with second-order kinetic model.At a pH of 2,the temperature was 50 ℃,the reaction time was 180 min under conditions of immobilization sericin of Sb3+ adsorption equilibrium,adsorption equilibrium amount of 94.89 mg/g,3.Through in-depth study of the actual heavy metal waste water treatment,the results showed:immobilized sericin gel beads for removal of heavy metals were high,water quality after the adsorption treatment could on the verge of "drinking water health standards"(GB5749-2006).4.Before and after of sericin protein immobilization,immobilization of sericin protein gel balls adsorption of heavy metals of the microstructure were compared.From the SEM image could see clearly that chitosan gel beads surface was very smooth.After immobilization sericin,its surface becames rough and uneven,you could see a lot of chain substance.After the adsorption of heavy metal,the material surface was shorter chain and was able to see white spherical particles attached to the top.By XRD diffraction analysis could know,Cd2+ and Sb3+ complexed with the immobilized sericin,weakening the original crystalline structure that the crystallinity of immobilized sericin was reduced.The O-H bond length of immobilized sericin after adsorption of heavy metal ions was shortened,and the peak area of amide I and amide Ⅱ band slightly reduced.It was showed that metal ions had influence on the conformation of immobilized sericin.