Ehanced Phosphate Removal By Preparation Of Acrylic Polymer-supported Hydrated Ferric Oxide Nanoparticles

In this study,FeCl₄^-ion exchange-NaOH precipitation-heat treatment was used to load nano-HFO onto acrylic anion exchange resin D213.Firstly,the preparation conditions?FeC13 and NaOH concentration?were optimized,and the material properties and adsorption properties of the compound adsorbents were investigated.The compound adsorbent HFO-D213 with the best performance was screened out.Subsequently,the influence rule and action mechanism of dosage,competitive ion,time and temperature were expounded,and the adsorption mechanism of phosphorus were revealed.Through the static adsorption-elution and fixed bed experiments,the adsorption and elution performance of HFO-D213 was investigated when recycling,providing theoretical basis and technical support for its application in deep phosphorus removal of sewage.The main results are as follows:?1?Six kinds of compound adsorbents were prepared by adjusting and controlling FeC13 concentration in the "ion exchange" stage.The results of material characterization showed that the HFO loading capacity of the compound adsorbent was between 4.6%and 17.1%,and the loaded HFO belonged to nano-scale with amorphous form.The distribution of HFO in the compound adsorbent showed U-shape.However,partial pores of the compound adsorbent were blocked after loading HFO,resulting in a slight decrease in the average pore size.The static adsorption experiment showed that both too high and too low HFO loading capacity were not conducive to the adsorption of phosphorus by the composite adsorbent.When the loading capacity of HFO was 14.8%,the adsorption capacity of phosphorus was the largest.The fitting results of pseudo-first order kinetic showed that the higher the HFO loading was,the slower the adsorption rate of compound adsorbent was.The optimum pH of compound adsorbent was 6-8.When the SO₄^2-concentration was>600 mg/L,the adsorption of D213 could be blocked.The adsorption and elution were stable in the repeated experiments.In conclusion,it was found that the compound adsorbent HFO-D213-14.8 with 14.8%loading capacity had the best adsorption performance when FeC13 concentration was 1.2 mol/L.?2?Three kinds of compound adsorbents were prepared by adjusting and controlling the concentration of NaOH in the "in-situ precipitation" stage.The results of material characterization showed that the increase of NaOH concentration had no significant effect on the loading capacity of HFO in the compound adsorbent.The loading capacity of HFO ranged from 14.1%to 14.9%,and the loaded HFO belonged to nano-scale with amorphous form.The higher the concentration of NaOH was,the more homogeneous the distribution of HFO in the compound adsorbent was.The experimental results showed that the adsorption capacity of HFO-D213-1.5M was lower than that of the other two compound adsorbents.However,there was no significant difference in adsorption kinetics among three compound adsorbents.The optimum pH of three compound adsorbents was 6-8.According to the comprehensive adsorption performance and NaOH dosage,HFO-D213-3M was screened out as the best.?3?The adsorption properties and mechanism of HFO-D213 compound adsorbent prepared under the optimum conditions?1.2 mol/L FeC13+3 mol/L NaOH?were investigated.The results showed that when the removal eff-iciency of P reached the maximum,the dosage of HFO-D213 was 0.5g/L.Different inorganic anions have different inhibitory effects on the adsorption performance of HFO-D213,and the inhibition effect was as follows from strong to weak:SO₄^2->NO3->Cl-The equilibrium time of HFO-D213 was 240 min.The results of thermodynamic analysis showed that ?G<0,?H>0 and ?S>0 in the adsorption process of HDF-D213 for P belonged to endothermic spontaneous reactions.By XPS,FT-IR and SEM-EDX,it was proved that the adsorption effect of the HFO-D213 on P was composed of the coordination effect of HFO on P and the electrostatic adsorption effect of quaternary ammonium group in D213.Repeated experiments with multiple batches showed that HFO-D213 had good adsorption performance and strong reusability.In the fixed bed experiment,taking the total phosphorus concentration of the effluent at 0.5mg/L as the breakthrough point,and the water flow of the simulated wastewater was about 1500 BV,while the actual water flow of the secondary effluent was about 860 BV.The elution rate of 5%NaOH+5%NaCl mixture could reach 100%.Based on the optimization of HFO-D213 preparation conditions,the studies on adsorption mechanism,adsorption performance and fixed bed application were carried out.It was found that HFO-D213 had the characteristics of high selectivity,strong anti-interference ability,good adsorption performance and strong stability,which provides theoretical support for further practical application of HFO-D213.