Phosphorus Removal Efficiency In Groundwater Of Iron Oxide Modified Halloysite Nanotubes And Its Mechanism

With the rapid progress of society,a large amount of phosphorus-containing wastewater generated by human life and production is directly discharged into water bodies without treatment,which will result in the water body not being able to completely purify the excessively discharged phosphates and finally cause the groundwater phosphorus pollution.Once it enters in the human body,it will pose a threat to our health.The adsorption phosphorus removal method has the advantages of the fast adsorption speed,stable performance,no generation of toxic or harmful by-products,and strong regeneration ability.The choice of adsorption material is very important in the process of using the adsorption method.Aiming at phosphate contamination in groundwater,iron oxide modified halloysite nanotubes?HNTs?phosphorus removal agents were prepared in this study to investigate the phosphate adsorption effect in groundwater.Screen the best reaction conditions through static single-factor batch experiments and response surface;Use many means to characterize materials before and after modification and phosphorus absorption,analyze the adsorption mechanism;1Fe-HNT dynamic phosphorus removal experiments were performed and the dynamic adsorption parameters were determined.Thomas model,Yoon-Nelson model,Adams-Bohart model and Wolborska model were used to fit the penetration curve.This study provides a theoretical and practical basis for groundwater phosphorus removal.The main results are as follows:?1?The three optimal reaction conditions are 1)4.9 g/L adsorbent dosage,p H=4.4,99.9 mg/L initial total phosphorus mass concentration;2)3.0 g/L adsorbent dosage,p H=6.9,99.8 mg/L initial total phosphorus mass concentration;3)2.9 g/L adsorbent dosage;p H=10.2,99.8 mg/L initial total phosphorus mass concentration.The adsorption capacities of iron oxide modified HNTs under the three conditions were6.279 mg/g,5.664 mg/g and 5.634 mg/g,respectively.The reaction reached equilibrium in 240 minutes;the increase in iron loading and initial phosphate concentration will increase the adsorption capacity of the adsorbent;coexisting ions(SO₄^2-,NO₃^-,Cl^-)did not significantly inhibit the removal of phosphorus by the adsorbent;the regeneration cycle of the adsorbent After 5 uses,the phosphorus removal rate decreased from 72.58%to 69.20%.?2?TEM,XRD,XRF,FT-IR,and BET characterization methods were used to characterize the micromorphology,chemical composition,and structure of HNTs before and after modification.After the phosphorus removal of HNTs and 1Fe-HNT,the zeta potential and other potential points shifted to the left,which proves that the two phosphorus removal mechanisms are electrostatic adsorption.In addition,the two phosphorus removal mechanisms include ligand exchange and Lewis acid-base interaction.?3?Adsorbent quality,inlet water flow rate,and inlet phosphate concentration have significant effects on the dynamic adsorption and phosphorus removal performance of 1Fe-HNT:increasing the mass of the adsorbent causes the penetration point and the depletion point to move backward,and the increase of the inlet water flow rate and the intake phosphate concentration causes the penetration point and the depletion point to move forward;Yoon-Nelson model can better describe the 1Fe-HNT dynamic adsorption phosphorus removal process.Therefore,in the process of 1Fe-HNT dynamic adsorption and phosphorus removal,chemical adsorption is the main factor.