Construction Of ZrO₂-TiO₂ Nanofiber Materials And Their Application In Phosphate Monitoring In Water

Water eutrophication is one of the most important environmental issues in the world.The content of dissolved orthophosphate in water directly affects the degree of eutrophication.Therefore,it is necessary to establish a simple,reliable and efficient method for monitoring phosphate in water.DGT(Diffusive Gradients in Thin Films)technology is based on Fick’s first law of diffusion.By selecting different diffusion phase and binding phase materials,the time weighted average concentration of the target in a certain period of time can be obtained quantitatively,which can effectively reflect the concentration of the target in a certain period of time.It is an ideal method for evaluating the concentration of soluble orthophosphate in water and the eutrophication of water.The main purpose of this paper is to establish a method of collecting soluble orthophosphate in water environment by using DGT technology.The major results and contents of are as follows:Firstly,ZrO2-TiO2 composite fibers with high specific surface area were prepared by electrospinning.The results of SEM,TEM,XRD,FT-IR and nitrogen adsorption show that the ZrO2-TiO2 composite fiber material has a low crystallinity mixed phase structure of ZrO2 and TiO2.The three elements of Zr,Ti and O are evenly distributed in the material,with mesoporous structure,and the specific surface area is about 110 m2 g-1.This electrospinning method for preparing mesoporous ZrO2-TiO2 fiber material is simple,and ZrO2 is evenly distributed in the fiber with high specific surface area.It is expected to be used as a binding phase material for collecting and monitoring orthophosphate in water by DGT technology.Then,this paper established a DGT method to collect phosphate in water using ZrO2-TiO2 composite fiber as binding phase and nitrocellulose membrane as diffusive phase.The diffusion coefficient of phosphate was determined by diffusion cell method.The availability and influence factors of phosphate in ZrO2-TiO2 fiber material gel-DGT device were studied.The experimental results show that the average diffusion coefficient of phosphate through nitrocellulose membrane is 4.78×10-6 cm2 s-1,under the laboratory conditions,the ZrO2-TiO2 fiber material gel-DGT device was applied to phosphate collection.The cumulative mass of phosphate increased with the increase of the layout time,and showed a good linear relationship.The phosphate concentration(CDGT)predicted by DGT had good correlation with phosphate concentration(CSOL)in the solution.When the pH of bulk solution is in the range of 3-9,the ionic strength is 1 ×10-6 to 0.1 mol·L-1,there is no obvious change in the binding capacity of ZrO2-TiO2 fiber gel-DGT to phosphate.Therefore,the DGT device based on ZrO2-TiO2 composite fiber material can provide a reliable passive sampling tool and method for quantitative collection of phosphate in water.