Study On Two Zirconium Containing Adsorption Materials For Phosphate Control In Lakes And Reservoirs

The removal of phosphate from source-separated urine is an efficient approach to reduce the P-load in receiving waters due to its high P concentration and low volume in wastewater.Therefore,a highly efficient adsorbent is imperative for this purpose.Metal-organic frameworks（MOFs）have recently attracted a lot of attention in adsorption due to their outstanding physicochemical features.In this study,we examined four Zr-based MOFs（UiO-66,UiO-66-NO₂,UiO-66-Br and UiO-66-NH₂）for the adsorption of phosphate from acidified urine.1)Our results indicated that the zirconium content,pore size and crystallinity are driving forces for the adsorption process.2)UiO-66-NH₂displayed the highest adsorption capacity（153.9 mg/g）at 25°C and p H 4.Phosphate in urine could be nearly totally depleted（>99%removal）using UiO-66-NH₂ at a dosage≥13.5 g/L.3)Elevating temperature and lowering p H are effective strategies to enhance the adsorption performance.The reduction of the isoelectric point of UiO-66-NH₂ after P uptake,the activation energy of the adsorption process estimated using Arrhenius equation（63.1 k J/mol）,FTIR spectroscopy and XPS suggested that inner-sphere complexation between phosphate and Zr atoms in the MOFs was the key adsorption mechanism.The performance of adsorption-desorption-regeneration using real human urine was verified.In the aspect of controlling endogenous phosphorus,in-situ sediment mulching technology has been widely used in controlling the release of it from eutrophication of water.In this study,the synthesis of zeolite and zirconium loaded zeolite from sediment was studied.The results show that:1)When the calcination temperature is 700℃,the calcination time is 60 minutes,the crystallization time is 6 hours,the mass ratio of Na OH to sediment is 1.2:1,and the liquid-solid ratio of hydrothermal crystallization is 15:1,higher purity of Nap1 zeolite can be obtained,and the maximum adsorption capacity of ammonia nitrogen is 27.027 mg/g.2)Zirconium modified zeolite can greatly improve the phosphate adsorption capacity of synthetic zeolite.The Langmuir model is used to fit the maximum phosphate adsorption capacity of 24.57mg/g and ammonia nitrogen adsorption capacity of 53.19mg/g.3)43 days in-situ covering experiment shows that zirconium loaded zeolite has good phosphate control capacity in practical application,which can make TP,DTP and DIP stable at a lower concentration,and zirconium loaded zeolite has a strong ability to fix dissolved orthophosphate.It is a kind of sediment covering material with wide application prospects for the control of endogenous phosphorus in lakes.To sum up,this study explored the control performance of two kinds of zirconium containing adsorption materials,zirconium based MOFs and zirconium loaded zeolite in eutrophication water,respectively,from the aspects of adsorption mechanism,influencing factors,synthesis conditions and practical application.It provides a reliable reference for the application of two kinds of zirconium containing adsorption materials in eutrophication water treatment.