Design And Adsorption Performance Of Lanthanum-based Magnetic Adsorbent For Phosphorus Removal

At present,the control of eutrophication pollution caused by excessive phosphorus intake and multi-channel phosphorus recovery are the focus of attention in many countries.the solid-liquid separation and recovery of low concentration phosphate in water were studied.Based on the combination of adsorption separation desorption enrichment process,new nano materials of lanthanum based magnetic materials were constructed.By comparing the stable morphology of different magnetic material particles and enhancing the magnetic recovery stability of adsorbents;Detailed adsorption experiments and adsorption desorption cycle experiments were carried out to explore the practical application potential of adsorbent and the possibility of recovering low phosphorus concentration in water.Firstly,La（OH）₃,La₂（CO₃）₃,La₂O₃·x H₂O and La₂O₃were prepared by conventional precipitation methods.The coexisting ions,p H value,adsorption isotherm and adsorption mechanism of four lanthanum materials for phosphate adsorption were studied.The results showed that the four lanthanum materials can adapt to the p H range of 4-8 and maintain good selective adsorption performance.Among the four materials,La₂（CO₃）₃had the highest phosphorus removal efficiency,the adsorption process was monomolecule adsorption and the saturated adsorption capacity was 81.71 mg/g.The phosphate sorption was due to the internal complexation of La-P-O.Secondly,three kinds of magnetic materials Fe₃O₄,γ-Fe₂O₃and Fe₃O₄/Si O₂were successfully prepared by coprecipitation method,and the best magnetic material was selected for magnetic modification of lanthanum carbonate.The magnetic recovery efficiency of the three materials was further discussed by turbidity.The results showed that the magnetic recovery efficiency ofγ-Fe₂O₃was maximum.Soγ-Fe₂O₃was selected to modify La₂（CO₃）₃.The results showed that urea was the best binder,La/Fe molar ratio was 1.5:1,the maximum adsorption capacity was 18.75 mg/g.Then,for the La₂（CO₃）₃/γ-Fe₂O₃magnetic lanthanum based materials under the optimum preparation conditions,the static adsorption experiments and adsorption mechanism of phosphate on La₂（CO₃）₃/γ-Fe₂O₃were researched,including p H value,coexisting ions,adsorption kinetics and adsorption isotherm.The results showed that the material can be used in most water at p H 3-8,and the coexisting ions had little influence on the adsorption.After adsorption for 6 h,the adsorption capacity reached saturation,the adsorption capacity was 25.15 mg/g.The Langmuir isotherm and pseudo second order kinetic model describe the adsorption process better,which indicated that the adsorption of phosphate on La₂（CO₃）₃/γ-Fe₂O₃material is mainly monolayer chemical adsorption.The adsorption mechanism of La₂（CO₃）₃/γ-Fe₂O₃for phosphate was attributed to electrostatic action and coordination action.Finally,the desorption performance of La₂（CO₃）₃/γ-Fe₂O₃adsorption of phosphate was studied,and the application ability of actual water was investigated.The results showed that the best desorption agent was the mixture of 2 mol/L Na₂CO₃and 1 mol/L Na OH,and The optimal desorption time was 6 h.The desorption process conform to the second-order desorption kinetics.The adsorption and desorption of La₂（CO₃）₃/γ-Fe₂O₃was further carried out by using the new adsorbent for 20 times.After the first 13 times of regeneration,the adsorption capacity of La₂（CO₃）₃/γ-Fe₂O₃could be maintained at more than 90%of the previous cycle;when the same adsorbent was used for 20 times,the regeneration results of the first 12 adsorption and desorption cycles could still be maintained at more than 90%of the previous cycle.This adsorption desorption process can realize phosphate enrichemnet.The phosphate adsorption test in real water further confirmed the applicability of the material in complex water.