Removal of Nitrogen Oxides by Using Expanded Graphite Synergy with Polyethylene Glycol
|Keywords||Expanded Graphite Polyethylene-300 Nitrogen Oxides Adsorption|
Expanded graphite is an excellent adsorption material with porous carbon, and it has been widely used in the field of removing environmental pollutants in recent years for its large specific surface area, effective adsorption, low environmental load, etc. Its adsorption and removal of dye wastewater, formaldehyde and other organic gas is effective. The research on the acid gaseous pollutants is still in the early stage.In the paper,80 meshes of natural flake graphite as raw material are made into expanded graphite with 280 ml/g of ratio of expansion,2.72 wt.% of ash,5.00 wt.% of volatile, and 2.12 wt.% of water through the process of acid intercalation, washing, drying, and heat expansion. Its N2 adsorption-desorption isotherms is measured under 77K by specific surface area analyzer, and its specific surface area, pore volume and pore size distribution are calculated by Langmuir equation, BET equation, t diagram method and BJH method. Viewing the micro-structure of expanded graphite with Scanning Electron Microscope (SEM), the researcher found that there was developed gap structure with different pore sizes on the surface of expanded graphite, and the shape of the pores were oval, crack or irregular ones. The researcher studied on the group of expanded graphite, and analyzed the effect of the group in the process of nitrogen oxides adsorption with Fourier transform infrared (FT-IR) analysis.The experiment of expanded graphite adsorbing nitrogen oxides approached the factors of affecting the adsorption properties of expanded graphite---amount of adsorbent, flow rate, initial concentration and adsorption temperature, and determined the optimum technological conditions by using factor analysis and orthogonal experimental design. The factors arranged by the different influence on the adsorption properties from big to small are initial concentration, adsorption temperature, amount of adsorbent and flow rate. The optimum technological combination is 0℃of the adsorption temperature,0.252 min of flow rate,184mg/L of nitrogen oxides’initial concentration,0.1 Og of expanded graphite (EG), and under this circumstances, the nitrogen oxides removal rate reached to 41.37%, and the adsorption capacity of unit expanded graphite was 380.6 mg. In addition, Langmuir, Freundlich, and Temkin equations predicted on the experiment data, and the experiment filled the Freundlich equation better. It suggests that the adsorption of nitrogen oxides by EG is polymolecular layer adsorption. The researcher analyzed the data by quasi-one and quasi-two adsorption kinetics model, and found that quasi-two model described the adsorption process better.The result of the research on the removal of nitrogen oxides by using expanded graphite synergy with polyethylene glycol-300 (PEG-300) indicates that the removal of nitrogen oxides is effective with the non-ionic surfactant PEG, and its removal rate may reach 90.03% for the low concentration NOx (0.5mol/L). The factors influenced on the removal result from big to small are initial concentration, flow rate, temperature, and mass adsorption. Optimum is:0℃of adsorption temperature,0.5 L/min of flow rate,0.025 mol of initial concentration,0.015 g of sorbent mass mixed 20 ml of PEG. Through quasi-one and quasi-two kinetics simulation of experimental data, the result suggests the quasi-one kinetics model is better fit. Thermodynamic parameters analyzed that whenΔG0 is negative, the reaction is spontaneous, and enthalpy is negative, which further confirmed that is the exothermic reaction. Spontaneous reaction of the system decreases with the increasing temperature, and the temperature increasing is not conductive to the removal of nitrogen oxides.To further explore the removal of high concentration nitrogen oxides, in this paper, by the use of pneumatic atomizer, the researcher took PEG-300 as absorbed liquid, expanded graphite as adsorption media, and selected the pneumatic atomizer to conduct an experiment of nitrogen oxides adsorption under the optimal parameters:0.74m of fog zone height,0.20-0.22mpa of jet pressure,0.5mm of both spay tube and jet tube,2000ml of polyethylene glycol (PEG-300),5.00 EG of self-expanding volume of 280 mL/g,150min of reaction time, and 73.85% of reached nitrogen oxides’removal efficiency.