Research On Zr Doped MgFe-LHDs As Phosphorus Adsorbent

Based on the contradiction between resource shortage and environmental pollution,this article prepares a kind of adsorbent with large adsorption capacity,easy to regenerate,and recyclable for the purpose of recovering phosphorus in water.It aims to solve environmental problems while recycling resources.Layered metal hydroxides(LDHs)and their calcined products(LDO)have a permanent positive charge layer and good anion exchange capacity,which can produce good adsorption effects on anions(such as phosphate)in water.Used as an anionic adsorbent,it’s adsorption capacity is mainly restricted by the composition of metal ions and the preparation conditions.Studies have shown that Zr4+ can combine with LDHs,and because Zr4+ has a stronger affinity with phosphate and higher cationic charge,it can increase the electrostatic attraction between the laminate and the phosphate,so consider doping Zr4+ to enhance the adsorption capacity of the material.The research results are listed here:The low saturation co-precipitation-hydrothermal crystallization method was used to synthesize MgFe-LDH with different Zr doping amounts,and it was obtained that when the fixed Mg:(Fe+Zr)=3:1,the doping ratio r=Zr4+:(Fe3++Zr4+)=20%,the adsorption capacity of the adsorbent prepared when calcined at 400℃ for 2h is the largest,which is 1.86 times the adsorption capacity of the previous undoped material;The initial pH of the solution will have a certain effect on the adsorption capacity,and the adsorption effect is best when pH=5;High-valent anions will reduce the adsorption capacity,while metal cations such as calcium and magnesium will increase the adsorption capacity;The adsorbent has a good removal effect on low-concentration phosphate;The adsorbent saturated with adsorption can be desorbed and regenerated with NaOH solution;After five cycles of regeneration,the adsorption capacity has only a limited decrease;The recycle of phosphate is realized by adding Ca(OH)2 to the desorption liquid.In the study of adsorption characteristics,it is found that the adsorption process is more consistent with the quasi-secondary reaction kinetic model.Due to the introduction of Zr4+ the adsorbent surface becomes uneven,which is more in line with the Feundlich isotherm model,and the adsorption capacity is significantly increased.Finally,through relevant analysis and characterization,the adsorption of Zr-LDO-20%on phosphate is mainly through the electrostatic attraction and surface coordination reaction between the phosphate and the metal laminate,as well as the interlayer anion exchange reaction and ion intercalation caused by the "memory effect" achieved.Therefore,the introduction of Zr4+ does increase the adsorption capacity,and provides certain experimental data and theoretical support for the research of phosphorus adsorbent.