Study On Preparation And Properties Of Gelatine-based Hydrogel Materials

The rapid development of modern industry has improved people's living conditions,however,it also brings a great many pollutions to the natural environment.And water pollution is one of the problems that have been troubling human beings for a long time,as the pollutions contents in discharge are too high to be self-purified by the natural environment.Especially,the heavy metal ions and dyes in waste water account for the main part of industrial contaminants.Generally,these two kinds of contaminants have the characteristics of high toxicity,difficult degradation,easy to accumulate in food chain and so on.Therefore,the treatment of wastewater containing heavy metal ions and dyes has become one of the most important topics in the field of water treatment.In the existing sewage treatment methods,adsorption method is widely used in the treatment of wastewater containing heavy metals and dyes due to its high adsorption efficiency,low cost,simple operation and no secondary pollution.Recently,the preparation of absorbents based on renewable biomass for the removal of dyes and heavy metal ions has been one of the important research directions of wastewater treatment.Gelatin,as one of cheap,eco-friendly and reproducible raw materials for absorbents,has attracted more and more attentions.However,the mechanical properties of most absorbents made from gelatin are poor.On the other hand,their adsorption capacities should be improved further.Thus,in this paper,new amphoteric hydrogel and gel beads based on gelatin and amphoteric polyvinylamine were prepared for the removal of dyes and heavy metal ions from water,respectively.An amphoteric hydrogel(G@PVAm-TGH)was prepared by using gelatin and amphoteric polyvinylamine as raw materials and glutamine transaminase as crosslinking agent.The structures and properties of G@PVAm-TGH were characterized by Fourier infrared spectrometer(FT-IR),sweep to electron microscopy(SEM),thermogravimetric analyzer(TG),and Zeta potentiometer.It was proved that the thermal stability of G@PVAm-TGH was higher than gelatin.Moreover,the isoelectric point of G@PVAm-TGH was about 6.64,which demonstrated that G@PVAm-TGH had distinct amphoteric properties.The swelling rate of G@PVAm-TGH in water was 22.87%.The results of adsorption experiments showed that its maximal adsorption capacity to acid fuchsin at p H 4 was 584.62 mg/g.The adsorption behaviors could be well fitted by Langmuir adsorption isotherm model and quasi secondary dynamics model.Furthermore,gel beads(G@PVAm-GGB)derived from gelatin and amphoteric polyvinylamine were prepared by reverse emulsion method in order to remove Cu(II)and Cr(VI)from water,in which liquid paraffin was used as solvent,Span-80 was used as emulsifying agent and glutaraldehyde was used as cross-linking agent.The structures and properties of G@PVAm-GGB were characterized by FT-IR,SEM and TG.The optimum p H values for removing of Cu(II)and Cr(VI)from water by the gel beads were 6 and 2,and its maximal adsorption capacities to Cu(II)and Cr(VI)were 21.44 mg/g and 18.41 mg/g,respectively.The adsorption mechanism of Cu(II)on G@PVAm-GGB was the coordination of amine groups on the gel beads with Cu(II),which could be well fitted by Langmuir adsorption isotherm model.However,the adsorption of Cr(VI)on G@PVAm-GGB was described well by Freundlich adsorption isotherm model,which proved that multi-layer Cr(VI)absorbed physically on the gel beads.