| Coal gangue is a kind of solid waste discharged from coal mining and washing process,bulk deposition of which will bring serious harm to the ecological environment.Instead,Coal gangue can be used as cheap raw material to synthesize zeolite adsorbent in virtue of its abundant SiO2 and Al2O3 composition.In this paper,zeolite A with higher ion exchange and adsorption performance was synthesized from coal gangue of Erdos,Inner Mongolia.The effects of Si O2/Al2O3,basicity,crystallization temperature and time on the structure and crystallization of the zeolite had been investigated.And the structure,morphology and chemical properties of zeolite A had been analyzed by using XRD,FT-IR,BET,SEM.zeolite A was used as adsorbent to treat Pb2+and Cd2+wastewater,and the adsorption process and mechanism were studied.It not only provided a cheap and effective adsorption material for the treatment of heavy metal wastewater,but also achieved the purpose of environmental protection.The main results were as follows:?1?Using coal gangue as raw material,zeolite adsorbent was synthesized by hydrothermal method.The influencing factors of zeolite A were investigated,The results showed that SiO2/Al2O3 determine the product,while the crystallization temperature and time have an effect on the nucleation of zeolite crystal,and the basicity of the system has a significant effect on the structure and crystal size of the zeolite.zeolite A could be synthesized under the condition of low SiO2/Al2O3.zeolite A is converted into zeolite SOD when the crystallization temperature is too high or the crystallization time is too long,and it is stable in neutral or weak alkaline medium.Therefore,zeolite A can be synthesized when the SiO2/Al2O3 is 1.5,the crystallization temperature is 85-95?,the basicity of the system is n?Na2O?:n?SiO2?=1.0,and the crystallization time is 8 h.?2?The synthesized zeolite were analyzed by using XRD,FT-IR,BET,SEM.The results showed that zeolite A with cubic structure had been successfully synthesized.The average particle size is 3-4?m,and the specific surface area is about 4 m2·g-1,The pore size distribution of the zeolite A calculated by HK equation is between 0.4-0.8 nm.?3?The adsorption properties and influencing factors of zeolite A for the heavy metal wastewater were investigated.The results show that the amount of adsorbent,the p H value of solution,the initial concentration of heavy metal ions and the adsorption time were the main factors affecting the adsorption.The dosage of zeolite was 0.15 g,the initial p H of Pb2+?Cd2+were 4 and 6.28,and the initial concentration of heavy metal ions were 100 mg·L-1.At the same time,the removal rate and adsorption capacity of Pb2+and Cd2+on zeolite A were 96.23%?32.08 mg·g-11 and 94.86%?31.62 mg·g-11 respectively.The adsorption process of Pb2+and Cd2+on zeolite A could be described by pseudo-secondary adsorption rate equation,which indicated that the adsorption process was chemical adsorption.The Weber-Morris equation shows that intraparticle diffusion was not the only rate control step in the adsorption process,and the rate control step before reaching equilibrium may be affected by both liquid film diffusion and intraparticle diffusion.?4?The isothermal adsorption showed that the Langmuir adsorption isotherm model?R2>0.9992?could better describe the adsorption process of Pb2+and Cd2+on zeolite A,which indicated that the adsorption process was monolayer adsorption and obtained the maximum saturated adsorption capacity of Pb2+and Cd2+was 51.28 mg·g-11 and 49.26 mg·g-1,respectively.The RL were in the range of 0 to 1,indicated that the adsorption of Pb2+and Cd2+on zeolite A was easy to occur.?5?Compared the adsorption properties of coal gangue with zeolite A,the results showed that the adsorption capacity of Pb2+and Cd2+was about 1.9times as much as that of coal gangue,which proved that the adsorption ability of the zeolite A is good. |
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