Investigation Of Controllable Synthesis Of Magnetic Mesoporous Silica NZVI@mesoSiO₂ And Removal Of Trichlorophenol And Tetracycline

Nanoscale zero-valent iron?nZVI?has unique advantages in water pollution remediation,but the easy agglomeration and oxidation characteristics make it has great limitations in practical application.Magnetic mesoporous silica nanocomposite is a new compound material with a modification of the nZVI to avoid particles agglomeration and being oxidized.The combination of metal nanomaterials and the mesoporous silica makes it complemental in superiority for both of them and renders all the advantages of mesoporous silica fully exerted.It has broad application prospects in the removal of refractory organic pollutants in water.The nZVI@mesoSiO₂ nanocomposites with nZVI cores were successfully prepared through a novel two-step method.With 2,4,6-trichlorophenol?2,4,6-TCP?as the target pollutant,the effect of preparation conditions on material morphology,crystal structure and pollutant removal performance were investigated and the crystal growth mechanism of magnetic mesoporous silica was revealed,which realizes the controllable synthesis of nZVI@mesoSiO₂.The optimum preparation conditions were obtained that were:n?CTAB/NaOH?=4.6/1,TEOS dosage is 5mL,the volume ratio of the absolute ethanol and oxalate is 2:1,the extraction time is 2h and the amount of iron source was 2.78g.The factors affecting the degradation of 2,4,6-TCP were studied using the nZVI@mesoSiO₂ particles synthesized under the optimum conditions.The optimum reaction conditions were as follows:nZVI@mesoSiO₂=1.00g·L^-1,[2,4,6-TCP]=20mg·L^-1,T=25?,pH=5.00.Then the impact of interfering substances in nature on the system was explored.It was found that Cl^-1 ions had little effect on the reaction process;SO₄^2-ions had inhibitory effect on the reaction;cations inhibited the reaction in the order of Ca²⁺>Mg²⁺>Na⁺>K⁺;EDTA could complex with Fe ions to prevent the passivation of nZVI core and promote the adsorption-reduction process,but the promotion effect was limited.HA is liable to form complex with2,4,6-TCP and bind with silicon hydroxyl groups on the surface of materials,which would compete with 2,4,6-TCP for active sites.so HA can inhibit the adsorption and reduction of nZVI@mesoSiO₂ to 2,4,6-TCP.The stability analysis experiment of nZVI@mesoSiO₂ showed that the material had good thermal stability,hydrothermal stability and dispersion stability,which means it has certain feasibility in practical application.The morphological and structure changes of nZVI@mesoSiO₂ before and after reaction were investigated.A series of characterization techniques such as SEM,TEM,BET and XPS were used to analyze the surface morphology,crystal structure and corrosion layer composition of nZVI@mesoSiO₂ before and after reaction.The results showed that the iron oxides formed on the surface after the reaction were Fe₃O₄,?-Fe₂O₃ and?-FeOOH.The dominant one in the reaction system is Fe²⁺ions.The results of GC-MS determination of intermediate products showed that nZVI@mesoSiO₂ could achieve reductive dechlorination and further generate ring-opening products.The characteristics of nZVI@mesoSiO₂ in removing pollutants under binary system were investigated.2,4,6-TCP and tetracycline?TC?were used as target pollutants to explore the relationship between 2,4,6-TCP and TC in binary system.The interactions showed that the presence of 2,4,6-TCP promoted and inhibited TC significantly higher than the presence of TC on the promotion and inhibition of 2,4,6-TCP.The intermediate products in the binary system were analyzed by GC-MS and LC-MS to explore the degradation process under the binary system.