The Study Of Porous Zirconium Modified Montmorillonite Composite On The Control Of Sediment Internal Phosphorus Loading In Small Scale Water Bodies

Phosphorus is a key factor in water eutrophication.The internal source of phosphorus have gradually decreased with the strengthening of environmental protection technology and the construction of rural sewage pipe network in recent years,however,the external source of phosphorus release has become the main source of phosphorus in water bodies.Phosphorus passivation materials have attracted much attention in the field of ecological restoration and treatment of water environment because of their simple operation and obvious phosphorus control effect.Small scale water bodies were mostly accepted by livestock and poultry farming with high organic content,the general phosphorus removal material was difficult to resist the impact of dissolved organic matter and made it more difficult to passivate phosphorus.Based on this,this paper prepared porous zirconium modified montmorillonite composite（SA@Zr MT/BC）with zirconium-based modified materials,evaluated the phosphorus removal performance of the composites by static adsorption experiments and multiple characterization means,revealed its phosphorus removal mechanism,clarified the effect of dissolved organic matter on the phosphorus removal of the composites,and explored the controling effect of the composites on the endogenous phosphorus in sediment.SA@Zr MT/BC was successfully prepared using the cross-linking method,and its well-developed pore structure and large specific surface area were demonstrated by SEM-EDS and BET,p H and coexisting ions have little effect on the adsorption of phosphate.The phosphate adsorption by SA@Zr MT/BC was an exothermic reaction with a reaction rate controlled by chemisorption,and the maximum adsorption amount was 25.77 mg/g.The XPS results showed that the phosphate adsorption mechanism of SA@Zr MT/BC followed the ligand exchange and the inner-phere complexing.There was a weak competition between humic/fulvic acid and phosphate,a few characteristic adsorption sites belonging to humic/fulvic acid were present on SA@Zr MT/BC.The effect of humic/fulvic acid concentration was small on phosphorus removal by SA@Zr MT/BC at 0-150 mg/L.When phosphate was not present,the maximum adsorption of humic/fulvic acid was 71.89,88.83 mg/g;when phosphate was present,the maximum adsorption was reduced by 34.84%,56.25%.Humic/fulvic acids with small molecular weight and high polarity were preferentially adsorbed by SA@Zr MT/BC,and the main mechanisms of absorption were electrostatic attraction,hydrogen bonding,and ligand exchange.The internal phosphorus release in the sediment is mainly in the form of inorganic phosphorus.The phosphorus content of the overlying water is kept in the range of 0.03-0.07mg/L within 42 days of the composite material covering,and the weakly adsorbed phosphorus（NH₄Cl-P）and the redox-sensitive phosphorus（BD-P）transformed to a relatively stable phosphorus form,and the passive phosphorus forms on the composites were mainly the metal hydroxide-bound phosphorus（Na OH）and the residual phosphorus（Res-P）.The dissolution amount of composite Zr⁴⁺was in the range of 1.25-3.10μg/L,which was far below the safety threshold for fish（15 mg/L）.