Preparation And Adsorption Performence On Copper Ions Of Pickering Emulsions Hydrogels

As a three-dimensional networks of crosslinked polymers which can retain large volumes of water,hydrogels have been widely used to treat various containments in water,in addition,it also been be used as an ideal carrier for encapsulating special adsorbents/extractants.Among the methods for encapsulating special reagents inside the hydrogels,Pickering emulsion based polymerization is an ideal strategy.Pickering emulsions is a special dispersion system that solid particles are used as the emulsifiers,which can effectively prevent the droplets from coalescence and endow it with excellent stability.Moreover,special modifications to the solid particles will bring additional properties to the Pickering emulsions or the polymers.Therefore,the combination of hydrogels and Pickering emulsions brings new ideas for the preparation of green and potential adsorbents.In this thesis,Pickering emulsions was introduced in the preparation of hydrogels,and the solid particles were specially modified.Hydrogel microspheres with controllable particle size,Pickering emulsion hydrogels(PEHGs)encapsulating extractants and PEHG microbeads were prepared.The specific research contents were as follows:(1)Poly(acrylic acid-co-acrylamide)hydrogel microspheres were prepared using hydrophobically modified silica N20 as the emulsifiers of W/O Pickering emulsions.The diameter(D)of the hydrogel microspheres was inversely proportional to the dosage(S)of hydrophobic silica.The size of hydrogel microspheres mainly affected the adsorption equilibrium time.There was no difference in the total amount of Cu2+adsorbed with different sizes,and the optimal pH value(=5)was obtained from the maximum adsorption capacity of 85 mg/g.The hydrogel microspheres adsorbed Cu2+through chemical interactions chiefly.Pickering emulsion polymerization was an effective and environmentally friendly method for manufacturing granular hydrogels.(2)Dual 3D network Pickering emulsion hydrogels(PEHGs)encapsulating copper extractant N902 were prepared by polymerizing continues phase of O/W Pickering emulsions.PEHGs were characterized by SEM,TGA and compression tests.Static and fixed-bed adsorption experiments for Cu2+ were also carried out.Due to the 3D hydrogel networks and the 3D particle networks in PEHGs,the encapsulation efficiency of the extractant reached 99%,and the leakage of the extractant was negligible.The critical crash pressure of PEHGs(Φoil=40%v/v)was 30.08 kPa,and the maximum deformation rate was 0.7.The saturated extraction capacity of the extractants in PEHGs was higher than that of liquid-liquid extraction.The adsorption capacity of the fixed-bed(10.12 mg/g)for Cu2+ was consistent with the predicted value of Langmuir isotherm model.After 65 cycles,the amount of Cu2+ adsorbed on PEHGs was 97.5%of the initial value,without extractant leakage and quality loss.(3)PEHG microbeads were prepared by O/W/O Pickering emulsions by a one-step method.O/W Pickering emulsions were stabilized by silane KH-570 modified silica with and hydrophobic silica H30 was used as lipophilic particles.In an O/W/O Pickering emulsion,the solid particle-polymer networks formed by the polymerizing KH-570 and acrylamide could effectively prevent the internal and external oil phases from cross contamination.The optimal heating time of O/W emulsions was 30 min,and the addition of acrylamide in water phase further improved the stability of O/W emulsions.The rate of Cu2+ adsorbed by PEHG microbeads with different sizes was different but same in amount adsorbed,which was directly related to the volume ratio of the encapsulated extractants.The fixed-bed adsorption experiment was completed in 250 min,and the Cu2+ adsorbed on the fixed-bed could be completely desorbed.