Study On The Preparation Of Iron - Modified Mg-Al Layered Double Hydroxides And Its Adsorption Of Phosphate In Wastewater

In recent years,due to the development of human production activities,excessive phosphorus enters the water body,resulting in serious eutrophication of the water body,which attracts the attention of all countries.Phosphate removal from wastewater by adsorption is a promising technology,the preparation of a kind of adsorbent material with practical application and excellent performance is of great significance to the solution of water eutrophication.Layered Double Hydroxides?LDHs?is an efficient and easily modified adsorbent.In this paper,the magnetic adsorbent FeMgAl-Cl LDH modified by iron was formed by introducing iron into the preparation process of MgAl LDH as the basic material.The adsorption properties of Fe-modified FeMgAl-Cl LDH magnetic adsorbent for phosphorus in water were studied.The influencing factors of its adsorption effect,adsorption isotherm and adsorption kinetics were analyzed.The adsorption of Fe-modified FeMgAl-Cl LDH magnetic adsorbent was discussed by means of FTIR,XRD,XPS and SEM-EDX The mechanism and the possibility of its practical application are verified.The main research contents and results are as follows:?1?FeMgAl-Cl LDH adsorbent was prepared by hydrothermal method and ion exchange method.The addition of Fe increases the hydroxyl density on the surface of the adsorbent,increases the surface charge and improves the adsorption capacity.The VSM characterization material has magnetism,which solves the separation problem of adsorbent from water after reaction.The adsorbents prepared with different dosages of Fe?0 mM,10mM,15 mM and 20 mM?were optimized.The results showed that the adsorbent with initial dosage of 15 mM FeCl₂·4H₂O was the better adsorbent.?2?Various factors affecting the adsorption performance were explored.Including dosage,pH,reaction temperature,reaction time,initial concentration of reaction,coexisting anions and so on.The results showed that the adsorption capacity decreased with the increase of dosage,pH and reaction temperature.With the increase of reaction time and initial concentration,the adsorption capacity increased first and then remained unchanged.The influence of coexisting anions on the adsorption of phosphorus by adsorbents is NO₃^-<Cl^-<SO₄^2-<HCO₃^-.?3?The fitting of adsorption isotherm conforms to Langmuir isotherm equation,indicating that the adsorption of phosphorus in water by adsorbent is attached to the monolayer adsorption,and the maximum adsorption capacity is 176.06 mg/g,which is close to the actual value?170.5 mg/g?.The analysis of adsorption kinetics conforms to quasi-second-order kinetics,indicating that the adsorption process is dominated by chemical adsorption.?4?Adsorption mechanism and practical application of FeMgAl-Cl LDH for phosphorus.In addition to physical adsorption,FeMgAl-Cl LDH adsorbs phosphorus in water mainly through ligand exchange and ion exchange.On the one hand,the hydroxyl?-OH?and phosphate on the surface of adsorbent exchange ligands to form a complex between phosphate and metal;on the other hand,the chloride ion?Cl^-?in the adsorbent intercalation exchanges with phosphate,and the phosphate ion enters the intercalation.The experiments of humic acid addition,cation addition and actual wastewater treatment proved that FeMgAl-Cl LDH can be applied to phosphorus removal in actual water,and it is an effective means to control eutrophication of water body.FeMgAl-Cl LDH magnetic adsorbent can be applied to the efficient removal of phosphate radicals in practice.It has important reference significance for the preparation of magnetic adsorbent,the removal of phosphate radicals and the prevention and control of water eutrophication.