Experimental Study On Removal Of Nitrogen And Phosphorus From Water By Potassium Ferrate Promoted By Reductive Ions

The problem of global water environmental pollution is becoming more and more serious,especially the harm of eutrophication.Traditional water treatment agents have the disadvantages of single performance,easy to cause secondary pollution and poor adaptability to water quality.Therefore,it is of great significance for the research and development of new water treatment agents with multiple efficacy and environmental protection.Potassium ferrate has the characteristics of oxidation,flocculation and sterilization,the removal of pollutants in water by potassium ferrate is of great theoretical significance for the treatment of eutrophication.The removal effect of Potassium Ferrate on nitrogen and phosphorus in water was studied by using the oxidation and Flocculation Characteristics of potassium ferrate and the enhancement of oxidation properties of potassium ferrate by reducing agent.The reaction mechanism was discussed by means of scanning electron microscopy?SEM?and other characterization methods.The main results are as follows:?1?Orthogonal experiments were used to optimize the reaction conditions as follows:The mixing speed was 350 r/min,the mixing time was 20 s,the oxidation speed was 140 r/min,the oxidation time was 15 min,the flocculation speed was 70 r/min,the flocculation time was 15 min,and the precipitation time was 10 min.?2?The removal efficiency of nitrogen and phosphorus in water was affected by the dosage of potassium ferrate,dosage mode and pH value.With the increase of potassium ferrate dosage,the removal rate of total phosphorus increased from 8%to 82%,and the removal rate of total nitrogen was about 3%.Under wet and dry conditions,the removal rates of total phosphorus and total nitrogen were 87%and 75%respectively,and 5%and 3%respectively.Under acidic and alkaline conditions,the removal rates of total phosphorus and total nitrogen were 87%and 70%respectively,and 2%and 3%respectively.?3?Reductive ions could promote the removal of nitrogen and phosphorus from water by potassium ferrate.Under neutral conditions,when the molar ratio of Fe⁶⁺to Fe²⁺was 1:1,1:1.5 and1:2,the removal rates of total phosphorus and total nitrogen were 88%,92%and 90%respectively,and 5%,4%and 5%respectively.When the molar ratio of Fe⁶⁺to I^-was 1:1,1:1.5 and 1:2,the removal rates of total phosphorus were 65%,58%and 56%,respectively,and the removal rates of total nitrogen were about 4%.?4?Fourier transform infrared spectroscopy?FTIR?analysis showed that most of the phosphorus in the precipitated products existed in the form of FePO₄ precipitation.Scanning electron microscopy?SEM?analysis showed that the precipitates were mainly formed by adsorption and aggregation of spherical nanoparticles.X-ray diffraction?XRD?analysis showed that the presence of Fe²⁺promoted the removal of phosphorus by potassium ferrate.In the reaction process,potassium ferrate oxidized most of phosphorus in different valence forms to+5 valence phosphorus,resulting in PO₄^3-,which reacted with the decomposition product of potassium ferrate to form FePO₄precipitation.?5?The XPS narrow scan spectra of N element showed that N element existed in the form of NH₃,NH₄⁺,NO₃^-and other combined nitrogen.In the oxidation stage,potassium ferrate oxidized macromolecule nitrogen-containing organic matter to intermediate state or inorganic nitrogen-containing compound molecule,Finally,in the flocculation stage,these nitrogen-containing compounds were precipitated by complex complexes and Fe?OH?₃ adsorption or by net trapping and sweeping,and finally separated from water.