Preparation Of Magnetic Carbonsilicon Composite Material From Coal Gasification Fine Slag And Its Adsorption Performance

Coal gasification slag is a by-product of the coal gasification industry.With the development of the economy,its production is increasing day by day.At present,the disposal of coal gasification slag is mainly landfill,and while occupying land resources,there is also a serious risk of environmental pollution.Carbon-silicon composite material is composed of activated carbon and mesoporous silicon.It has the characteristics of large specific surface area,good thermal stability and abundant surface active groups.It is a good adsorbent.However,it is difficult to separate and recycle carbon-silicon composite materials after adsorption,and magnetic separation is a separation method with simple operation and high efficiency.Therefore,this paper studies the magnetic carbon based on the preparation of carbon-silicon composite materials from coal gasification fine slag.The preparation of silicon composite material and its adsorption performance for Pb(?)are expected to provide a theoretical basis for the resource utilization of coal gasification fine slag.The main conclusions are as follows:(1)Using K₂CO₃ as the activator,a carbon-silicon composite material(denoted as K-CSC)was prepared by a chemical activation method.As the activation temperature,activation time,and alkali-carbon ratio increase,the methylene blue adsorption value and the iodine adsorption value both show It first increases and then decreases.As the concentration of hydrochloric acid increases,the methylene blue adsorption value and iodine adsorption value first increase,and then tend to stabilize.The best preparation conditions:activation temperature 850?,activation time 60 min,The ratio of alkali to carbon is 3,and the concentration of hydrochloric acid is 15%.Under these conditions,the prepared carbon-silicon composite K-CSC has a specific surface area of 886 m²/g and a pore volume of 0.75 cm³/g.Using water vapor as the activator,a carbon-silicon composite material(denoted as H-CSC)was prepared by physical activation method.The concentration of hydrochloric acid and the acid leaching time are the main factors affecting the adsorption value of H-CSC methylene blue,and the activation temperature and activation time are the main factors affecting the adsorption value of iodine.The best preparation conditions:activation temperature 850?,activation time 60 min,water vapor amount 0.3 m L/min,hydrochloric acid concentration 20%,acid leaching time 4 h.Under these conditions,the prepared H-CSC has a specific surface area of 765 m²/g and a pore volume of 0.64 cm³/g.According to XRF and TG,the impurities of K-CSC and H-CSC are basically removed after acid leaching and activation.XRD shows that the mesoporous silicon of H-CSC is amorphous,while K-CSC is mainly amorphous.And a small amount of crystalline silicon.FT-IR results show that the surfaces of H-CSC and K-CSC both contain hydroxyl,carboxyl and other functional groups,while K-CSC contains more silanol.According to TEM and SEM,both H-CSC and K-CSC carbon-silicon composite materials have abundant pore structures.(2)The magnetic carbon-silicon composite material(denoted as K-MCSC)is prepared by solvothermal method.Increasing the addition of Na Ac and the theoretical loading ratio of magnetic Fe₃O₄ can enhance the magnetic properties of K-MCSC,and the addition of Na Ac has an effect on K-The specific surface area and pore volume of MCSC have little effect.The theoretical loading ratio of magnetic Fe₃O₄ has a greater impact on the specific surface area and pore volume of K-MCSC.As the theoretical loading ratio of magnetic Fe₃O₄increases,the specific surface area of K-MCSC and The pore volume gradually decreases.The optimal preparation conditions are:the addition amount of Na Ac:0.06 mol/L,and the theoretical loading ratio of magnetic Fe₃O₄:10%.When the magnetic carbon-silicon composite material(denoted as H-MCSC)is prepared by the one-step method,increasing the activation temperature and the addition of Fe₂O₃can enhance the magnetic properties of H-MCSC,while the pore volume and specific surface area show a trend of first increasing and then decreasing.The best preparation conditions are:activation temperature 850?,Fe₂O₃ addition amount of 6%.XRD shows that the magnetic composition of K-MCSC is magnetic Fe₃O₄,while the magnetic composition of H-MCSC is magnetic elemental Fe and magnetic Fe₃O₄.The magnetic properties of the two are 6.22 emu/g and 5.87 emu/g,respectively.The separation is carried out by a magnet in a short time.It can be seen from SEM and TEM that the magnetic particles produced by the two preparation methods will block part of the pores,but when the H-MCSC is prepared by one-step magnetization,the magnetic source Fe₂O₃ has a catalytic activation effect,which makes the specific surface area slightly increase,so H-MCSC The pores are more abundant,with a specific surface area of 946m²/g and a pore volume of 0.728 cm³/g.(3)The adsorption laws of H-MCSC and K-CSC for Pb(II)in aqueous solution are similar.With the increase of adsorption time,the removal rate of Pb(II)increases,and finally stabilizes and reaches adsorption equilibrium.The amount of addition is directly proportional to the Pb(II)removal rate,and the initial lead ion concentration of the solution is inversely proportional to the Pb(II)removal rate.Increasing the p H of the solution under acidic conditions is beneficial to the improvement of the Pb(II)removal rate.Under the adsorption conditions of 0.04 g of adsorbent,p H=6,adsorption time of150 min,and initial Pb(II)concentration of 50 mg/L,the removal rate of Pb(II)by K-CSC and H-MCSC reached 98%And 92%.The adsorption of Pb(II)in aqueous solution by H-MCSC and K-CSC accords with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model.Among them,the adsorption performance of H-MCSC is better,and the maximum saturated adsorption capacity fitted by Langmuir It is 40.71 mg/g.