Magnetized Vermiculite Modified By Waste Rare Earth Polishing Powder To Recover Phosphorus In Water And Its Reuse For Lead Removal

Excessive concentrations of phosphate and heavy metal ions in water will cause serious harm to the ecological environment and human health.At present,there are many methods for removing phosphate and heavy metal ions in water,including chemical precipitation,ion exchange,membrane separation and adsorption.Compared with other methods,the adsorption method has the advantages of simple operation and reliable performance.It has the advantages of high removal efficiency and low cost.However,the adsorbents in the previous studies became invalid adsorbents after adsorbing phosphates and could not adsorb heavy metal ions again,so as to achieve the purpose of treating sewage with waste.In this study,a composite adsorbent（Mev-WP）was prepared by combining magnetized vermiculite（Mev）and waste rare earth polishing powder Ce La₂O₃F₃（WP）by acid leaching and advection precipitation methods for the recovery of phosphorus in water.The Mev-WP with reduced phosphorus absorption efficiency was desorbed to obtain a regenerated adsorbent（Mev-WP/P）for the removal of Pb²⁺in water.The prepared adsorbent not only has high adsorption capacity,but also has magnetic properties,which can be easily separated from water by using an external magnetic field,and can continue to adsorb lead after cyclic adsorption of phosphate,thus realizing the reuse of waste adsorbent.The influence of pH,coexisting ions,adsorption time and other factors on the adsorption process of the two adsorbents was investigated,and the adsorbents were characterized by X-ray powder diffractometer（XRD）,SEM,vibrating sample magnetometer（VSM）and XPS.The adsorption mechanism of phosphorus and lead removal was analyzed and analyzed,and the effect was verified by using urban sewage and mineral processing wastewater respectively.The specific results are as follows:The optimal doping mass ratio of waste polishing powder（WP）and magnetized vermiculite（Mev）is 5:5 to prepare Mev-WP for phosphate adsorption.At pH=3-11,with the increase of pH value,the composite The effect of adsorbing phosphorus gradually decreased,that is,it was helpful for Mev-WP to adsorb phosphate under acidic conditions,and the peak adsorption amount was 63.79 mg/g at pH=3 and 25℃;Among the four coexisting anions Cl^-,SO₄^2-,HCO₃^-,and NO₃^-,HCO₃^-has an inhibitory effect on the adsorption of phosphate,and the higher the concentration,the greater the degree of inhibition on the adsorption of phosphate;During the process of phosphate adsorption by Mev-WP,with the increase of initial phosphate concentration,the adsorption equilibrium time and equilibrium adsorption capacity increased;The Langmuir isotherm is more suitable for describing the adsorption process of phosphate by Mev-WP,that is,the adsorption process belongs to monolayer adsorption;the adsorption process of Mev-WP needs to absorb heat;the pseudo-second-order kinetics is more suitable for describing the adsorption of phosphate by Mev-WP The adsorption process is mainly chemical adsorption;the intraparticle diffusion model shows that the adsorption process is divided into three stages,and the boundary layer diffusion in the first stage is a fast adsorption stage.After 5 times of analysis and recycling,Mev-WP has a phosphorus recovery rate of65%,which has good reusability;The phosphate concentration was reduced from 1.3 mg/l to 0.01 mg/l within 1 h in the urban sewage deep phosphorus removal experiment.By FTIR,ZETA and XPS analysis,it can be seen that the adsorption mechanism of Mev-WP for phosphate adsorption is mainly that-PO₄groups replace-OH groups on La-OH and Ce-OH to form La-O-P and Ce-O-P coordination complexes compound to remove phosphorus.Mev-WP/P was obtained by desorbing Mev-WP whose efficiency decreased after cyclic adsorption of phosphate by using 0.1 mol/l Na OH solution for lead removal.In the experiment of adsorption of Pb²⁺ions by Mev-WP/P,when pH=1-6,with the gradual decrease of pH,the effect of regenerating adsorbent on adsorbing Pb²⁺ions is gradually weakened,that is,the low pH condition is not conducive to the adsorption of Pb2+by Mev-WP/P ions,reaching a peak adsorption capacity of 48.76mg/l at pH=6 and25°C;Among the four coexisting cations of Na⁺,K⁺,Ca²⁺and Mg²⁺,Ca²⁺and Mg²⁺ions will seriously inhibit the adsorption of Pb²⁺ions by Mev-WP/P,and because Ca²⁺ions and Pb²⁺ions have similar ionic radius and same ion valence,The inhibition of adsorption effect is greater;During the adsorption process of Mev-WP/P to Pb²⁺ions,the adsorption equilibrium time and equilibrium adsorption amount increased with the increase of the initial Pb²⁺ion concentration;Langmuir was more suitable to describe the process of Mev-WP/P adsorption of Pb²⁺ions,that is,the adsorption process belongs to Monolayer adsorption;adsorption of Pb²⁺ions is an endothermic reaction;Mev-WP/P adsorption of Pb²⁺ions is more in line with pseudo-second-order kinetics,that is,the adsorption process is mainly chemical adsorption.XRD,ZETA and FTIR analysis showed that the adsorption mechanism of Mev-WP/P for Pb²⁺ions was mainly the formation of complexes between PO₄^3-and Pb²⁺on Mev-WP/P to remove lead.The lead removal verification experiment of mineral processing wastewater shows that when the dosage of Mev-WP/P is 1g/L,the Pb²⁺ion concentration is reduced from 0.867mg/l to0mg/l within 30min.