| Polyacrylic acid(PAA)is an important polymer material which has a large number of carboxyl and hydroxyl functional groups,and PAA has broad application prospects in the treatment of heavy metal.In this paper,polyacrylic acid was selected as substrate and TiO2 prepared by sol-gel method as porogen to prepare Polyacrylic acid porous materials,which possessed porous structure,high adsorption rate and amazing adsorption property.First,TiO2 sol was prepared by using butyl titanate as raw materials,ethanol as asolvent,and glacial acetic acid as inhibitor which controlling hydrolysis and alcoholysis of butyl titanate.Then TiO2/PAA hybrid hydrogels were prepared by cross-linking of titanium dioxide and acrylic acid,and the effect of preparation process on the stability of hybrid hydrogels were investigated.Secondly,polyacrylic acid porous materials were prepared by using hydrochloric acid eluting titanium dioxide in hybrid hydrogels.The effects of various factors on polyacrylic acid porous materials adsorbed Cu(Ⅱ)ions were investigated,the optimum preparation process and adsorption conditions were determined:TiO2 sol 2.0 g,elution time 120 min,elution temperature 70 ℃,MBA 0.02 wt%(mass ratio of monomer of acrylic acid),adsorption temperature 30 ℃,initial pH=5,adsorption time 120 min,initial concentration of Cu(Ⅱ)ions 300 mg/L,and adsorbent was 0.8 g/L,the maximum adsorption capacity of Cu(Ⅱ)ions for polyacrylic acid porous materials was 300 mg/g,and the removal rate was 82.5%.FT-IR analysis showed that carboxyl group,hydroxyl group and amide group involved in the adsorption of Cu(Ⅱ)ions by polyacrylic acid porous materials.The results of Scanning electron microscopy(SEM)showed that TiO2 were evenly distributed in the hybrid hydrogels.The porous materials developed due to the elution of titanium dioxide,which was favorable to the adsorption of Cu(Ⅱ)ions by polyacrylic acid porous materials.Finally,the adsorption behavior of polyacrylic acid hybrid hydrogels and polyacrylic acid porous materials were investigated.The adsorption of Cu(Ⅱ)ions on the polyacrylic acid porous materials conformed to the Freundlich adsorption model,and the polyacrylic acid hybrid hydrogels were consistent Langmuir isotherm adsorption model.The results of adsorption kinetics study showed the pseudo-second-order kinetic model and the intra-particle diffusion model were fitted for both of polyacrylic acid porous materials and polyacrylic acid hybrid hydrogels,and the adsorption process was mainly chemical adsorption.The adsorption of the polyacrylic acid porous materials and the polyacrylic hybrid hydrogels was a spontaneous,exothermic and entropy decreasing process.The adsorption mechanism analysis results showed that the adsorption of polyacrylic acid porous materials for Cu(Ⅱ)ions was the result of the interaction of ion exchange,electrostatic attraction,surface complexation and other chemical adsorption and physical adsorption,in which Chemical adsorption was the dominant factor and pores causing by the elution of titanium dioxide enhances their physical adsorption.The adsorption capacity of polyacrylic acid porous materials with developed pores was not significantly reduced after six times of regeneration,and the reusability of the porous materials was improved by elution of titanium dioxide. |
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