Experimental Study On The Degradation Of Phenanthrene Contamination Of Groundwater In Coal Mine By Modified Nano-Zero-Valent Iron Activated Sodium Persulfate

Coal resources are closely related to groundwater resources.In recent years,groundwater pollution in coal mine areas caused by mining activities has been paid more and more attention.In this thesis,a kind of polydopamine loaded nano-zerovalent iron sulfide material was prepared to activate sodium persulfate to degrade the polycyclic aromatic hydrocarbon（PAHs）pollution in the groundwater of coal mine area in the way of advanced oxidation.The indoor sand column test was carried out to explore the migration of the remediation material,and the simulation box test was used to explore the remediation effect of the remediation material forming in situ oxidation reaction zone in the underground aquifers.The main research achievements of this thesis are as follows:（1）The nano zero-valent iron material（NZVI）was prepared by liquid phase reduction method,and the NZVI material was vulcanized（S-NZVI）,polydopamine loaded（PDA-NZVI）,polydopamine loaded-vulcanized（PDA-S-NZVI）;The four materials were characterized by a variety of means,and the suspension sedimentation test and corrosion aging test under aerobic conditions were carried out at the same time.The results showed that PDA-S-NZVI material had better dispersibility,better corrosion resistance and less agglomeration than other materials,and it had great advantages in activating sodium persulfate（PS）in the aqueous layer medium.The adsorption test showed that PDA-S-NZVI material had good adsorption.（2）The static degradation test of phenanthrene was carried out.Among different oxidation systems,the degradation efficiency of phenanthrene by PDA-S-NZVI@PS composite oxidation system was better than other systems,and the degradation rate could reach 85.31%.By discussing the degradation efficiency of phenanthrene by the oxidation system of PDA-S-NZVI@PS composite material under different influencing factors,it can be obtained that the degradation rate of phenanthrene can reach 92.23%when 0.3mg/L phenanthrene,p H=7,sodium persulfate concentration is 1.5m M,and PDA-S-NZVI material dosage is 0.3g/L.When the initial p H is acidic,the degradation rate of phenanthrene can reach 92.23%.The degradation efficiency could be further improved.Combined with the change trend of Fe³⁺and Fe²⁺concentration in the reaction process and the free radical quenching test,it is revealed that the degradation of the composite material to the pollutant phenanthrene is to produce sulfate free radicals and hydroxyl free radicals to oxidize and degrade the pollutant phenanthrene and the material itself also has the adsorption effect on the pollutant.（3）Sand column transport test was carried out to explore the migration effect of PDA-S-NZVI@PS composite material in the aquifer.The results showed that PDA-S-NZVI@PS composite material had better migration than the unmodified nano-zero-valent iron composite system,and it could form a large range of oxidation reaction bands.When the composite slurry flows through the surface of the small size medium of the aquifer,a large amount of composite slurry will be adsorbed and deposited.For a certain concentration of composite slurry,there is a maximum critical value for the effect of injection speed on its migration ability.High injection concentration can obtain high reaction efficiency,but it will reduce its own migration ability and adversely affect the formation of oxidation reaction band.In addition,according to the T-E model theory,the main mechanism of composite material migration in underground aquifer media is diffusion mechanism.The adsorption and intercept effect of the aquifer medium on the composite material and the gravity effect of the composite material itself have little effect on the migration.The aquifer is less efficient for its capture.（4）The experiment of PDA-S-NZVI@PS composite material in situ oxidative degradation of phenanthrene pollutants in groundwater of Coal Mine area in the aquifer of the simulated tank was carried out.It was found that the composite material formed a stable oxidation reaction zone in the downstream of the injection well,which could realize the effective remediation of phenanthrene contaminated groundwater by in-situ injection of remediation materials in the groundwater aquifer.At the same time,DO and p H decreased and ORP potential increased after injection,which provided favorable conditions for the oxidative degradation of phenanthrene.There are 47 figures,20 tables and 115 references in this thesis.