Removal And Recovery Of Phosphorus By NHFO/pumice Composite And Its Application In Resin Wastewater

Phosphorus is an essential nutrient element for all kinds of living things,and also one of the harmful factors for water environmental health.As phosphorus is a non-renewable resource with limited reserves,how to efficiently remove phosphorus from water and recycle it has gradually become a research focus.Traditional phosphorus removal methods are often ineffective in removing phosphorus from water.Phosphorus removal by adsorption is efficient and convenient and does not harm the environment.Therefore,the adsorption method is chosen as the efficient way to remove phosphorus from water.pumice is rich in resources and is a good porous solid phase adsorption material.However,the adsorption capacity ofpumice as adsorbent is limited,while the adsorption capacity of pumice as carrier is greatly increased.Nano Hydrous Ferric Oxide(NHFO)is widely used for phosphorus removal in water treatment due to its advantages of good chemical stability,large specific surface area and strong affinity for phosphorus.But NHFO particle size is small,easy to lose in the process of treatment,many studies fixed ferric hydrate in porous solid phase carrier.Therefore,this study intends to load NHFO ontopumice to prepare NHFO/pumice composite material,and combine with struvite crystallization method to recycle phosphorus in the phosphorous rich liquid formed after desorption agent.The main conclusions are as follows:(1)By changing the preparation conditions of NHFO/pumice composite,it can be concluded that when the concentration of HCl is 0.5 mol/L,the concentration of FeCl3 is 0.5 mol/L,and the heat treatment time is 12 h,the prepared NHFO/pumice composite has good adsorption and phosphorus removal performance.Compared with the adsorption effect of single adsorption material Y1,Y2 and Y3,it can be seen that the adsorption capacity ofpumice to phosphorus is greatly improved after loading NHFO,and the addition of NHFO makes NHFO/pumice composite become a better phosphorus removal adsorbent.(2)Scanning electron microscope(SEM)and X-ray photoelectron spectroscopy(XPS)were used to obtain the prepared NHFO/pumice composite.The pore structure of pumice was good,there were many particles on the surface of NHFO/pumice composite,and the fe hydrate loaded on the pumice was mainly in the form of FeOOH.X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)further proved that NHFO was successfully loaded ontopumice.(2)In order to study the adsorption performance of NHFO/pumice composites in different environments,the pH,temperature,coexisting anion concentration and ammonia nitrogen concentration can be obtained by changing the static experimental conditions.When the pH is 7,the adsorption capacity of NHFO/pumice composites for phosphorus reaches the maximum.The temperature change experiment shows that the adsorption process of NHFO/pumice composite is endothermic.When Cl-and SO42-coexist,the influence of SO42-on the adsorption capacity of NHFO/pumice composite is greater than that of Cl-,possibly because the charge of SO42-is more than that of Cl-;the adsorption capacity of NHFO/pumice composite was inhibited by high concentration of ammonia nitrogen.The adsorption capacity of NHFO/pumice composites increases with the increase of initial phosphorus concentration,and gradually reaches equilibrium.(3)In order to further study the mechanism of phosphorus removal by NHFO/pumice composite,Langmuir isotherm model and quasi-second-order kinetics show that the adsorption of phosphorus by NHFO/pumice composite is mainly monollayer adsorption and chemical adsorption.The diffusion model shows that the adsorption rate of phosphorus on NHFO/pumice composite is controlled by both the external mass transfer process and the diffusion step in the adsorbent,and the control step is not solely controlled by the internal diffusion step.FT-IR and XPS diagrams were used to analyze the NHFO/pumice composite after phosphorus removal by adsorption.It was found that Fe-OH bond on hydrated iron oxide complexed with phosphorus to form Fe-O-Fe-P bond,which verified that NHFO onpumice reacted with phosphorus and formed a complex.(4)In order to study the application of NHFO/pumice composite material in actual wastewater,a fixed-bed adsorption simulation experiment was designed.It was concluded that due to the complex composition of actual wastewater,some substances occupied the phosphorus removal site on the surface of NHFO/pumice,so that the treatment capacity of actual wastewater was less than that of simulated wastewater.However,the faster the actual wastewater flow rate is,the shorter the contact time with NHFO/pumice composite is,and the smaller the actual wastewater treatment capacity is.Through selection,0.2 mol/L NaOH solution as desorption agent for NHFO/pumice composite desorption effect is the best.After 0.2 mol/L NaOH solution was used as desorption agent for six times,the desorption effect of NaOH solution on NHFO/pumice composite decreased significantly due to the gradual increase of phosphorus in the solution,which was not conducive to the regeneration of phosphate root.(5)Phosphorus in the phosphorus-rich solution can be recovered by struvite crystallization method.When Mg:N:P is 1.2:3:1,the utilization ratio of phosphorus and N is the highest during struvite formation,and the crystal purity of struvite is good.When the pH value is 9-10,the phosphorus utilization during struvite crystal formation is the highest.Through XRD,FT-IR and XPS analysis of the structural characteristics of the synthesized struvite,functional groups and elemental morphology,it can be seen that the main component of the struvite is MgNH4PO4·6H2O.In this study,NHFO/pumice composite material was prepared bypumice and NHFO to analyze its adsorption and phosphorus removal performance under different environmental factors,explore its adsorption and phosphorus removal mechanism,and realize the recycling and utilization of phosphorus resources by removing phosphorus from the surface of NHFO/pumice composite material to form struvite.It provides theoretical basis for the application of NHFO/pumice composite material in practical engineering,and has certain practical significance.Figure[30]table[6]reference[113]...