Preparation Of Inorganic Porous Adsorbent By Gasification Fly Ash And Its Removal Of Cr(?) In Water

Cr(?)pollution has great harm to the ecological environment and has carcinogenic effects.China is a large industrial country.So the large amount of waste containing Cr(?)wastewater discharged from industrial production causes serious pollution of water.In addition,China faces serious water shortage problems.Therefore the prevention and control of Cr(?)pollution is imminent,and the adsorption method for treating heavy metal wastewater is obvious and easy to operate.The gasification fly ash used in this paper comes from Shenhua Ningdong Coal-to-Oil Company.Preparation of gasification fly ash-based inorganic porous adsorbent by alkali fusion hydrothermal synthesis method.The cation exchange capacity of adsorbents prepared under different ash to alkali ratio,aging time,crystallization temperature and crystallization time was determined by formaldehyde method.The product was characterized by XRD,SEM,FTIR,BET and MIP.The adsorption equilibrium experiment of Cr(?)solution under different conditions was carried out using the prepared gasification fly ash-based porous adsorbent,and its adsorption characteristics were analyzed by kinetics and thermodynamics.The gasification fly ash is mainly composed of glass beads coated with aluminosilicate.The surface of the particles is smooth and flat.The average particle size of fly ash is 40.51?m,and the content of silicon and aluminum is 51.86%and18.38%,respectively.The BET and MIP method shows that the micropores in the gasification fly ash are mainly distributed at 0.5-0.8nm,the mesopores are mainly distributed at 7-15nm,the BET specific surface area is 27.56 m~2/g,and the average pore diameter is 6.12 nm.The macropores are mainly distributed between 10?m and100?m.When the ratio of ash to alkali ratio is 1:1,the aging time is 15h,the crystallization temperature is 120°C,and the crystallization time is 10h,the prepared cation exchange capacity of the porous adsorbent is the highest,which is about 13times higher than the CEC value of the raw material.Compared with gasification fly ash,the product treated by alkali-hydrothermal method has a significantly improved surface roughness and a rich pore structure.There was a positive correlation between the number of micropores in the product and the CEC value,and there was no significant correlation between the number of macropores and the CEC value.The adsorption of Cr(?)by inorganic porous materials follows the quasi-secondary kinetic model and the intraparticle diffusion model.Through the analysis of Langmuir,Freundlich and Redlich-Peterson isotherm models,the adsorption process of Cr(?)by inorganic porous material is more consistent with Langmuir model,which indicates that the adsorption is single-layer coverage and the maximum single-layer adsorption capacity is 180.59mg./g.Through the calculation of the thermodynamic parameters of the adsorption process,the adsorption of Cr(?)by the porous material is a spontaneous endothermic process,and the adsorption process belongs to physical adsorption.The paper has 23 pictures,10 tables,and 104 references.