Efficiency And Mechanism Of Potassium Ferrate On The Removal Of Se(?) And Cr(?) Wastewater

Water heavy metal pollution has always been an important environmental problem that plagues people.On the one hand,the heavy metal composition in the water body is complex,stable.Heavy metals are also difficult to purify naturally through water bodies and difficult to be degraded by microorganisms.The heavy metal composition can only accumulate in the water body,resulting in increasing pollution,causing great harm to humans and aquatic organisms.Heavy metals are widely used and play an important role in China's medical,aerospace,infrastructure,transportation and other fields,and improper disposal of heavy metals will limit industrial development and social progress,thereby reducing people's living standards.Therefore,it is necessary to find a reasonable and effective water heavy metal treatment technology.Potassium ferrate?K₂Fe O₄,Fe????,as a multifunctional new green water treatment agent,has the functions of oxidation,flocculation,sterilization,disinfection and deodorization.It has great potential in the field of water treatment and is very suitable for being taken to study the treatment of heavy metal pollution in water.This paper study the efficiency and mechanism of potassium ferrate on the removal of Se??? and Cr???wastewater.This paper first comprehensively investigated the effects of various factors on the performance of potassium ferrate in removing Se??? in water,including the in-situ and ex-situ of potassium ferrate,the initial pH of the solution,the adsorption isotherm,etc.,and then explored the Fe/Mn molar ratio,the effect of initial pH,in-situ and coexisting ions on the effect of Mn??? to enhance the removal of Cr??? by potassium ferrate.At the same time,we also used X-ray diffraction?XRD?,transmission electron microscopy?TEM?,Fourier transform infrared spectroscopy?FTIR? and X-ray photoelectron spectroscopy?XPS? to characterize and analyze the physical and chemical properties of the samples before and after the reaction and proposed the specific mechanism by which potassium ferrate removes the separate pollution of Se??? and Cr??? in water.The main results of the study are as follows:?1?Potassium ferrate can effectively remove Se??? wastewater.When the initial pH is2.5,the removal efficiency of 0.5 g/L potassium ferrate to 100 m L of 10.0 mg/L Se???can reach 97.0%.By fitting with the Langmuir adsorption isotherm model,it was found that as the initial concentration of Se???increases,the removal amount of Se??? by per unit of potassium ferrate will continue to increase.The maximum removal amount is 204.20 mg/g,which is better than the commonly used Se???wastewater treatment agent.But at the same time,this efficient removal ability is significantly affected by the initial pH of the solution.The exploration results of different initial pH indicate that the removal of Se??? by potassium ferrate is more rapid and efficient under acidic conditions,but as the p H of the solution increases,the removal efficiency of Se???will drop significantly.?2?Characterization and analysis of the physical and chemical properties of the sample before and after the reaction of potassium ferrate removal Se??? by XRD,FTIR and XPS.It was found that the reduction product of potassium ferrate is a crystalline double-stranded ferrihydrite,specifically composed of?-Fe OOH and?-Fe₂O₃,and its surface active site has a good effect of adsorbing Se???.During the removal process,Se??? in the solution will be oxidized by Fe??? to Se???.Meanwhile,Fe??? is reduced to ferric solid particles,thereby further removing selenium ions in the water.The reduction products of Fe??? have different adsorption and removal methods for Se??? and Se??? ions present in the solution.Se??? can form inner sphere complexes with Fe??? reduction products through ligand exchange mechanism,while Se??? adsorbs on Fe???reduction by interacting with the surface charge of Fe??? reduction products to from the outer spherical complex,and the binding mode of Se??? is more unstable than that of Se???.?3?Mn??? can enhance the performance of potassium ferrate in removing Cr???.When the Fe/Mn molar ratio is 2:3 and the initial pH is 7.0,the removal efficiency of Mn??? enhanced potassium ferrate to remove Cr???can reach 99.7%,which is significantly better than that of potassium ferrate alone to remove Cr??? up to 85.1%.Moreover,this high removal efficiency has stability and is less affected by the solution pH.This is shown in the initial pH range of 3.0-8.0 explored by the study,the removal efficiency of Cr??? has not changed much;in addition,this high removal efficiency is basically not affected by the in-situ removal of potassium ferrate and the coexistence of ion bicarbonate?HCO₃^-?and calcium(Ca²⁺).In this study,except for the coexisting ion sulfate(SO₄^2-),other influencing factors will not change the effect of Mn?II?to enhance the removal of Cr??? by potassium ferrate.?4?Through XRD,FTIR,TEM and XPS,the characterization and analysis of the physical and chemical properties of the samples before and after the Cr???removal reaction.It revealed that Fe???can be combined with the solution Mn???in water undergoes an oxygen reduction reaction with water molecules to produce solid particles of manganese oxide?Mn O_x?and ferric oxide.The resulting reduction products of MnO_x and Fe???can also be used as adsorbents,showing a strong adsorption capacity for Cr??? and maintaining a high removal effect in a wide pH range.This is because compared with MnO_x,Fe??? reduction products can only adsorb Cr??? by electrostatic attraction to form a simple outer spherical complex.Such a combination is unstable and susceptible to the p H of the solution,while MnO_x can adsorb Cr??? to form a more stable internal spherical complex,which makes its adsorption performance weakened by p H.At the same time,the Mn??? ions adsorbed on the surface of the Fe??? reduction products,on the one hand,increases the positive charge on the surface of the reduction products,providing more favorable conditions for Cr???adsorption,on the other hand,it also forms the?-Fe₂O₃-Mn??? complex can reduce the adsorbed Cr??? to Cr?? ?,thereby reducing the toxicity of the entire adsorbed products.