Preparation Of Molecularly Imprinted TNT Material And Study On TCE Adsorption On Soil

With the improvement of industrialization and rapid economic growth,the problem of environmental pollution has also become increasingly serious.TCE as a typical soil volatile organic pollutant and TNT as the main pollution component of explosive wastewater,soil and groundwater pollution has become the focus of environmental field.Due to the low solubility of the two substances and the difficulty of biodegradation,they can exist in the natural environment for a long time.At present,the treatment methods for the two pollutants are relatively simple,mainly focused on physical adsorption and advanced oxidation,with high cost,easy to form secondary pollution and other shortcomings.However,the adsorption method is economical and efficient,and has been widely used at home and abroad.In this study,TNT molecularly imprinted polymer synthesis and TCE soil remediation were studied.In the synthesis aspect of TNT molecularly imprinted polymers,TNT molecularly imprinted polymer and TNT magnetic nano-molecularly imprinted polymer with high selectivity,good dispersibility and rapid adsorption were synthesized by water phase precipitation polymerization method.It was characterized by UV-vis,FTIR,ESEM,BET,and TGA.In addition,the adsorption kinetics,thermodynamics and selective adsorption of TNT on polymers were studied.Firstly,a novel water-phase imprinted polymer and water-phase non-imprinted polymer were synthesized by water phase precipitation polymerization method,with TNT as template molecule,am as functional monomer and EGDMA as crosslinking agent.The results show that selective imprinted polymers with stable structure can be synthesized by this method.The polymer can reach adsorption equilibrium within 200min.In 5 mmol/L TNT acetonitrile solution,the equilibrium adsorption capacity of the polymer is 263 mmol/kg.Scatchard fitting analysis shows that the electron-rich functional monomer acrylamide and the electron-deficient TNT benzene ring have a strong charge transfer effect,which can form a relatively stable complex.In addition,the cross-linking agent EGDMA has the obvious feature of delaying the phase separation time of the polymer reaction,so that high-quality imprinted materials can be synthesized.Compared with water-phase non-imprinted polymers,water-phase imprinted polymers exhibit higher adsorption rate,larger adsorption capacity and higher selectivity for TNT.Compared with the structural analog DNT,the specificity of selection for TNT is mainly due to the imprinted holes on the surface of CMIP.Fe₃O₄material has the characteristics of strong rigidity,non-expansion,easy surface modification and rapid solid-liquid separation under the condition of external magnetic field.Therefore,Fe₃O₄particles are particularly suitable for preparing the core of molecularly imprinted materials.In this paper,after modifying the surface of nano-Fe₃O₄particles,a two-step aqueous precipitation polymerization method was used to synthesize nano-magnetic molecularly imprinted polymers with selective adsorption sites on the surface,so as to achieve rapid adsorption and separation.The results show that magnetic molecularly imprinted polymers with small particle size and uniform dispersion can be prepared by adding appropriate amount of sodium dodecylbenzene sulfonate.The amount of TNT adsorbed by the polymer can be improved by adding the functional monomer with positive charge.Compared with the non-magnetic molecularly imprinted polymer,the adsorption capacity of the magnetic molecularly imprinted polymers is increased by 38 mmol/kg,indicating that Fe₃O₄particle synthetic polymers can further effectively improve the specific adsorption capacity of molecularly imprinted polymers.This is mainly because the recognition sites in the above materials can not be used effectively.The magnetic nano-TNT molecularly imprinted polymer has the characteristics of uniform particle size distribution,larger specific surface area,higher selectivity,better dispersion,and can be quickly adsorbed and separated.In the study of TCE contaminated soil,high temperature oxidation?375?,600??and low oxidation sodium hypochlorite oxidation were used to treat the soil,and the adsorption process and mechanism of TCE by different soil components?soft carbon,hard carbon,and minerals?were studied.Based on the static adsorption experiment,the influencing factors of TCE adsorption on soil were studied.Through high temperature oxidation and sodium hypochlorite oxidation method to deal with the soil,with organic matter content is0.96%of the soil samples and 375?,600?,sodium hypochlorite and combined oxidation?600?+sodium hypochlorite?of soil samples as adsorbents,the various soil adsorption of TCE adsorption kinetics and adsorption thermodynamics,the content of soft soil carbon,hard carbon,and minerals in the soil,the initial concentration of TCE and the strength of calcium ion on the adsorption were studied.The results show that the soil adsorption of TCE on soil can be divided into three stages:fast adsorption,slow adsorption and equilibrium.The adsorption equilibrium of TCE can be achieved in about 30 hours,and the adsorption capacity of TCE in the fast adsorption stage can reach about 70%of the total adsorption capacity.According to the adsorption kinetics and thermodynamics,it is found that the adsorption process conforms to the quasi-second-order kinetic equation?R²>98%?.And the soil adsorption of TCE is mainly physical adsorption.According to the study of soft carbon,hard carbon and minerals in soil,it is found that the adsorption of TCE by soil samples is the result of of the combined action of organic matter and minerals.Among them,the hard carbon in organic matter plays a major role in the adsorption of TCE,and the contribution rate of adsorption is more than 60%,while the minerals also play a certain role in the adsorption of TCE.The increase of TCE concentration can increase the contribution rate of mineral adsorption.The increase of ionic strength(Ca²⁺)significantly reduced the adsorption effect of TCE by various soil components.