Adsorption And Mechanism Of NHFO@pumice On Ammonia Nitrogen

Ammonia nitrogen is one of the factors leading to water eutrophication,which causes serious harm to water environment.Because of its wide source,low price and recyclability,many scholars have done a lot of research on the removal of ammonia nitrogen by adsorption.Honeycomb stone in our country is rich in reserves,there are extremely rich pore structure,is a good solid phase carrier material,but the adsorption capacity of ammonia nitrogen is limited;Nano Hydrous Ferric Oxide（NHFO）is a commonly used adsorbent in water treatment.It has the characteristics of large specific surface area,high activity,and stable chemical properties,but it is easy to lose when used alone.Therefore,nano-hydrous ferric oxide is loaded on pumice.To study the adsorption performance and mechanism of NHFO@pumice composite material for ammonia nitrogen,and to lay a theoretical foundation for the application of NHFO@pumice in practical wastewater.It has certain guiding significance to remove ammonia nitrogen from actual wastewater by adsorption method.In this study,the NHFO@pumice composite was successfully prepared by loading nano-hydrated iron oxide onto honeycomb stone by co-precipitation method.SEM-EDS、BET and XRD were used to characterize the structural morphology,elemental composition,pore distribution,and crystal structure of NHFO@pumice.By changing the environmental conditions（p H,coexisting cation concentration,initial ammonia nitrogen concentration,dosage）,the adsorption performance of NHFO@pumice was studied.XPS and FT-IR were used to characterize NHFO@pumice,analyze the element distribution and functional group changes of NHFO@pumice,and explore the mechanism of NHFO@pumice adsorption of ammonia nitrogen.Then,NHFO@pumice composite was used for the adsorption and desorption of actual wastewater,and the ammonia nitrogen in the desorption solution was recovered by strutite method.The work done is as follows:（1）NHFO@pumice was successfully prepared by co-precipitation method.Wh en the concentration of Na Cl was 0.5 mol/L,the concentration of Fe Cl₃·6H₂O was0.5 mol/L,and the contact time was 12 h,the adsorption performance of NHFO@pumice was the best,and the maximum adsorption capacity was 3.909 mg/g.By co mparing the adsorption effect of honeycomb stone,nano-hydrated iron oxide and N HFO@pumice on ammonia nitrogen,it can be seen that the adsorption performance of pumice loaded with nano-hydrated iron oxide on ammonia nitrogen is stronger th an that of single sorbent.SEM characterization results showed that the pore structur e of honeycomb stone was developed,and there were many spherical particles onth e surface of honeycomb stone after loading.EDS showed that iron and nitrogenele ments were embedded in NHFO@pumice.BET results showed that the nitrogenadso rption-desorption isotherm of NHFO@pumice belonged to typeⅣisotherm.The X RD results showed that the nano-hydrated iron oxide loaded onto the pumice was mainly in the form of Fe OOH.（2）Environmental factors significantly affected the adsorption performance of NHFO@pumice.According to the change of p H,the optimal p H value was about 7.The coexistence of H⁺,Na⁺,K⁺and Mg²⁺ions inhibited the adsorption of NHFO@pumice more strongly than the presence of each ion alone.The optimal adsorption effect was obtained when the initial concentration of ammonia nitrogen was 20 mg/L.The dosage of NHFO@pumice was 0.5 g,and the best effect was obtained.（3）Studying the mechanism of NHFO@pumice on ammonia nitrogen will he lp to improve the adsorption performance of NHFO@pumice.The results of model study showed that the Langmuir isotherm model was more consistent with the adso rption behavior of NHFO@pumice,with a correlation coefficient of R²=0.9886.The quasi-second-order kinetics was more consistent with the adsorption behavior of NH FO@pumice,indicating that the adsorption of NHFO@pumice was mainly controll edby chemical adsorption behavior.Elovich model further confirmed that NHFO@pu mice adsorption of ammonia nitrogen was chemical adsorption.XPS analysis showe d that the mechanism of NHFO@pumice adsorption of ammonia nitrogen was main ly ion exchange.FT-IR characterization analysis showed that the adsorption processo f NH₄⁺by NHFO@pumice included the process of water absorption and the electro static interaction between NH₄⁺in solution and hydroxy groups on NHFO@pumice.（4）NHFO@pumice has good adsorption performance for actual wastewater.According to the penetration curve,NHFO@pumice reaches the penetration point earlier for the actual wastewater treatment than the simulated wastewater treatment.The larger the actual wastewater flow rate,the earlier the penetration point of NHFO@pumice for ammonia nitrogen adsorption in wastewater.0.5 mol/L Na Cl+Na OH solution was the best desorption agent for NHFO@pumice,and the desorption rate reached 81.4%.After six cycles,the desorption rate decreased to 61.2%.（5）The recovery of ammonia nitrogen from the desorption solution by struvite crystallization is of great practical significance.When Mg:N:P was 1:3.6:1.2 and p H was about 9,the N utilization rate of the desorption solution was the highest during the formation of struvite,and the purity of the struvite crystal was the best.XRD and FT-IR methods were used to characterize the crystal structure and functional group changes of the synthesized precipitate.The XRD results showed that the crystal structure of the synthesized precipitate was highly consistent with the standard diffraction peak of struvite.The FT-IR results further confirmed that the synthesized crystal was Mg NH₄PO₄·6H₂O in the struvite precipitate.Figure[27]table[11]reference[103]...