Preparation Of Functionalized Zirconium Hydroxide Crosslinked Polyvinyl Alcohol Microspheres And Their Adsorption Performances Of Phosphorus

Phosphorus is a major nutrient pollutant.When the phosphorus-containing wastewater discharged into natural water bodies fails to meet the standards,the eutrophication will occur,resulting in a sharp deterioration of water bodies.At the same time,phosphorus is also an important and non-renewable resource,which is extremely important for industrial and agricultural production.Therefore,there is a urgent need to select a technology that can efficiently remove and recover phosphorus in wastewater to ensure sustainable supply of phosphorus resources and reduce environmental pollution.Adsorption is considered to be an effective method for the removal and recovery of phosphorus in sewage,while the key is the choice of a suitable adsorbent.In this study,poly?vinyl alcohol??PVA?was used as a carrier to introduce zirconium hydroxide acting as a cross-linker,in which the zirconium hydroxide cross-linked poly?vinyl alcohol?microspheres?PVA/ZR?were in situ formed by one-step encapsulation under the alkaline solution.Besides,the preprared PVA/ZR was surface-modified with triethylene tetramine?TETA?to successfully prepare the triethylene tetramine-functionlized zirconium hydroxide cross-linked poly?vinyl alcohol?microspheres?TETAPVA/ZR?.In order to improve the adsorption performance,magnetic zirconium hydroxide cross-linked PVA microsphere?mPVA/ZR?with a diameter of 250um was prepared by the droplet-based microfluidics technology.The composition and structural characteristics of mPVA/ZR were studied by different characterization methods.The performances of PVA/ZR,TETAPVA/ZR and mPVA/ZR for phosphorus removal were investigated under static batch experiments and dynamic adsorption column experiments.The main results are as follows.?1?The adsorption amount of phosphorus onto amino-functionalized TETAPVA/ZR was greatly improved compared to that of PVA/ZR.The PVA/ZR and TETAPVA/ZR were characterized by SEM,XRD,TG,FTIR and XPS.These adsorbents showed good spherical shape and stable property,.The static results showed that the adsorption processes of phosphate onto PVA/ZR and TETAPVA/ZR were favourable under acidic conditions.Besides,the adsorption processes of phosphate were less affected by Cl^-,SO₄^2-and NO₃^-ions,but were negatively affected by humic acid,fulvic acid and HCO₃^-.The presence of cations would improve the adsorption performance of PVA/ZR and TETAPVA/ZR.The adsorption processes of phosphate onto PVA/ZR and TETAPVA/ZR both conform to the pseudo-second-order kinetic model and the intraparticle diffusion model.The equilibrium isotherm experimental data were well described by the Freundlich model,suggesting heterogeneous multilayer sorption was dominant during the adsorption process.Desorption and regeneration experiments show tha the adsorbents exhibited good recyclability.The adsorption mechanisms of phosphate onto PVA/ZR and TETAPVA/ZR were mainly electrostatic interaction,ligand exchange and inner-sphere complexes.?2?The removal and recovery of phosphorus in actual sewage by PVA/ZR and TETAPVA/ZR were simulated.The results from the effect of adsorbent dosage and the dynamic adsorption-desorption in the column indicated that PVA/ZR and TETAPVA/ZR have great potential for the phosphorus removal and recovery from wastewater.The cations in wastewater may be involved in the adsorption process of phosphate,resulting in an increase of the adsorption capacity.The desorption efficiency of phosphate after column adsorption is above97%.?3?SEM,XRD,TG,FTIR,VSM,DLS and XPS were used to characterize mPVA/ZR,indicating that it had good morphology,stable properties and magnetic respons.The acidic conditions were beneficial for the adsorption of phosphate onto mPVA/ZR,which exhibited a certain selective adsorption capacity for phosphate.The adsorption of phosphate onto mPVA/ZR conforms to the pseudo-first-order kinetic model and the intra-particle diffusion model.The Freundlich model could better describe the experimental results,indicating that the adsorption process was dominated by multi-molecular heterogeneous adsorption.Desorption and regeneration results indicated that the adsorbents exhibited good recyclability.The adsorption mechanisms of phosphate onto mPVA/ZR were mainly the combination of electrostatic interaction,ligand exchange and inner-sphere complexes.