Preparation Of Transition Metal Polymer Support And Its Interaction Mechanism With Ammonia Ligand

Ganzhou in Jiangxi province is rich in rare earth resources and is praised as the"Kingdom of Rare Earths".The development and utilization of rare earth resources is accompanied by the production of high-salt ammonia nitrogen wastewater.As the national ammonia nitrogen emission requirements increase,the demand for new and environmentally friendly ammonia nitrogen treatment technologies is also increasing.Relying on the mechanism of ion exchange and adsorption,the ion exchange adsorption method has the advantages of high efficiency,fine stability,fantastic convenience and brief time in the treatment process,and has attracted the attention of related scholars.However,the presence of salt in the wastewater is resulting in the great reduction of the treatment efficiency of ammonia nitrogen in the ion exchange adsorption method.Based on the clarification of the spatial matching relationship between the transition metal ions,the polymer support and the coordination of ammonia,this paper uses the coordination of transition metal ions to solve this problem.In this paper,the simulated ammonia nitrogen wastewater prepared by ammonium chloride solution is the research and treatment object.Through the previous research on the polymer support data,four polymer supports（D001 resin,D751 resin,Montmorillonite（Moammo）and Diatomite（Diammo））and four transition metal ions(Co²⁺,Ni²⁺,Cu²⁺,Zn²⁺)were used to prepare metal-loaded polymer supports and applied to the comparative study of salt-free and high-salt ammonia-nitrogen wastewater.Based on the prepared metal-based polymer support,the influence of the system p H,the salt content of the solution,the dosage of polymer support and the adsorption time and other physical and chemical parameters were investigated.At the same time,the kinetic study was carried out,and modern characterization methods were used to determine the morphology and structural properties of the polymer support before and after the adsorption.On this basis,factors such as coexisting anions and cations,reaction temperature,initial concentration of ammonia nitrogen,desorbents,and stability of metal-based polymer supports were investigated.Finally,the metal-based polymer support was applied to the actual rare earth high-salt ammonia nitrogen wastewater treatment to verify its feasibility.The main conclusions of the experiment are as follows:（1）Compared with the salt-free ammonia nitrogen solution,the ammonia nitrogen removal performance of each metal-loaded polymer support（hereinafter referred to as"nitrogen removal"）under high salt conditions is significantly reduced,indicating that high salt conditions inhibit the nitrogen removal effect.Under the condition of high salt content simulated ammonia nitrogen wastewater,the four best metal-loaded polymer supports obtained are Ni-D001 resin,Cu-D751 resin,Cu-Moammo and Zn-Diammo.Among them,the best ammonia nitrogen removal rate and ammonia nitrogen adsorption amount obtained by metal-loaded Ni-D001 resin are 29.26%and 3.55 mg/g,respectively;the best ammonia nitrogen removal rate obtained by metal-loaded Cu-D751 resin,Cu-Moammo and Zn-Diammo and the adsorption capacity is 29.55%and 3.68 mg/g,39.04%and 4.83 mg/g,37.04%and 4.77 mg/g,respectively.（2）Static experiment have obtained the best conditions of removal of ammonia nitrogen using four fetal-loaded polymer supports under the high-salt content,including the Ni-D001 resin、Cu-D751 resin and Zn-Diammo（solution p H 11.0、solution salt content 4g/L、dosage 4 g/L、adsorption time 90 min）,Cu-Moammo（solution p H 10.5、solution salt content 4 g/L、resin dosage 4 g/L、adsorption time 90 min）.（3）In the experiment,three models of Quasi-first-order kinetic equation,Quasi-second-order kinetic equation and Elovich kinetic equation were utilized for comparative study to determine the mechanism of nitrogen removal.The results show that the kinetic fitting of the four polymer supports supported by four metal ions in the nitrogen removal process is more inclined to the Quasi-second kinetic equation,indicating that the nitrogen removal process of each metal-loaded polymer support is chemical adsorption process.In addition,using modern characterization methods,it is found that the modified metal-based polymer supports have their own frame intact,with increased specific surface area and more adsorption holes.The metal ions on the metal-loaded polymer support have successfully removed nitrogen,and the FT-IR、XPS spectra show that the main mechanism of nitrogen removal is indeed due to the coordination complex between ammonia molecules and metal ions,partly result from ion exchange and electrostatic adsorption removal effect.The specific performance is:the metal-loaded D001 resin had been tested after nitrogen removal,and FT-IR detected that the low-frequency fingerprint region contains O-M lattice vibration,and the"O-M-N"valence bond was found,indicating that the metal-loaded D001 resin successfully coordinated to remove nitrogen;The metal-loaded D751 resin had the FT-IR detection,and found that the blue shift of C=O symmetrical stretching vibration,the weakening or disappearance of the-NH₂ functional group,and the red shift of the bond of the O-M lattice vibration,together explain the metal loaded-D751 resin successfully coordinated adsorption nitrogen;The metal-loaded Moammo was detected by FT-IR and found containing Si-O-M bending vibrations,and N-M bonds were formed after nitrogen removal.XPS testing also showed that the metal-loaded Moammo successfully coordinated removing nitrogen;The metal-loaded Diammo itself contains Si-OH.The N1s spectrum obtained by XPS before and after nitrogen removal and the Si-O-M stretching vibration and the formation of the N-M bond found in the FT-IR spectrum jointly confirmed the nitrogen of coordination complex that occurred during the nitrogen removal process.（4）The comparative study results of the four best metal-loaded polymer supports show that co-existing cations affect the nitrogen removal performance of the metal-loaded polymer support to varying degrees,and multi-component,high-valence cations will more significantly affect the nitrogen removal process;Similarly,there are similar results under the condition of high valence anions;Temperature has little effect on the nitrogen removal process,while high ammonia nitrogen concentration will significantly enhance the adsorption capacity of ammonia nitrogen.The removal rate of ammonia nitrogen will first improve and then decrease.In order to ensure the recycling effect of adsorbents,the best ammonia nitrogen desorbents are finally determined as:Ni-D001-0.1M/L HCl,Cu-D751-0.1M/L Na Cl,Cu-Moammo-0.1M/L KOH and Zn-Diammo-1 M/L Na Cl;After five cycles of"adsorption-desorption-adsorption"treatment,the experiment found that Cu-D751 and Zn-Diammo can finally meet the adsorption capacity of 4 mg/g,so the stability is high;when applied to actual wastewater,the water environment is more to be complicated,the four best metal-loaded polymer supports are inhibited to varying degrees.Among them,Zn-Diammo has the best treatment effect,and Cu-D751 is the second.