Purification Of Ammonia Nitrogen And Phosphate Pollution In Surface Water By Modified Zeolite

To prevent the harm of eutrophication caused by high nitrogen and phosphorus content in natural water bodies,it is necessary to remove both ammonia nitrogen and phosphate at the same time.Previous studies have shown that biological and electrochemical technologies can effectively remove high concentrations of ammonia nitrogen and phosphate from water.As research on water conservation in China continues to develop,the standards for limiting ammonia nitrogen and phosphate in water have become increasingly strict.Therefore,it is particularly important to effectively treat low-concentration ammonia nitrogen and phosphate in surface water.Among various adsorption methods,natural zeolite has attracted wide attention due to its high cation exchange capacity and low market price.However,its adsorption effect on anions such as phosphate is poor,thus requiring modification treatment to improve its adsorption performance.In this study,a chemical impregnation method was used to modify natural zeolite with the aim of improving its selective adsorption of ammonia nitrogen and obtaining active functional groups for phosphate removal through an in-situ precipitation method.The ultimate goal was to achieve simultaneous treatment of low-concentration ammonia nitrogen and phosphate in water.To investigate the mechanism of modified zeolite for removing ammonia nitrogen and phosphate,various characterization methods were employed.Finally,to verify its practical application,the modified zeolite was used for treating surface water near a mining area in a certain province,aiming to attain feasibility support.The main conclusions are as follows:（1）The optimum removal efficiency of N-Z for ammonia nitrogen was achieved with a modification agent Na Cl concentration of 1 M,a modification solid-liquid ratio of 5 g/L,and a modification time of 7 hours.According to the Langmuir model,the theoretical maximum adsorption capacity was calculated as 4.574 mg/g.Additionally,10 CN-Z showed strong affinity for phosphate when prepared with a modification agent Cu（NO₃）₂ concentration of 30m M,a p H value of 9,and a modification solid-liquid ratio of 10 g/L,with a maximum adsorption capacity of 8.264 mg/g.（2）The main mechanism for N-Z to remove ammonia nitrogen is through ion exchange and monolayer adsorption,with spontaneous adsorption process.In the adsorption process of phosphate by 10 CN-Z,physical and chemical effects jointly acted while liquid film diffusion and particle diffusion limited the adsorption rate.Particle diffusion had a higher degree of restriction than liquid film diffusion on phosphate,and the adsorption process was also spontaneous.The FT-IR and XPS characterization results demonstrated that ammonia nitrogen exchanged with Na⁺on N-Z while 10 CN-Z could chemically bond with phosphate through hydroxyl group participation in the adsorption reaction.Thus,it can be considered that the main mechanism for N-Z to remove ammonia nitrogen is through ion exchange,while the mechanism for 10 CN-Z to remove phosphate is mainly based on electrostatic attraction and ligand exchange.（3）Under the condition of p H 7,common coexisting ions in surface water have a certain effect on the purification of ammonia nitrogen and phosphate by N-Z and 10 CN-Z.When the initial concentrations of ammonia nitrogen and phosphate in the actual water were 19.69 and0.32 mg/L,and the dosage of N-Z and 10 CN-Z were 15.0 g/L and 0.4 g/L,the removal rates of ammonia nitrogen and phosphate in the bisystem were 94.0%and 96.2%,respectively.The concentration of nitrogen and phosphorus in effluent meets the Class III water standard of Surface Water Environmental Quality Standard（GB3838-2002）...