Study On Synthesis Of Zeolites Using Laterite Nickel Slag And Its Separation Performance For CO₂/N₂

The consumption of fossil fuels has contributed to the emissions of global CO2increase sharply. Therefore, the capture and sequestration technology has great significance to reduce the emission of CO2. More effective and low-cost, green adsorbents should be developed with an increasing concern. Zeolites are widely used among adsorption materials. Using cheap mineral materials and industrial wastes synthesizing zeolites instead of chemical raw materials have great potential commercial value, and also are important to recycle the solid waste. Up to now, synthesis zeolites using laterite nickel slag as raw material have not been reported. In this study, a new approach for the synthesis of zeolites was developed using laterite nickel slag and bauxite, the separation properties of CO2and N2were also investigated.Firstly, high purity microporous4A zeolite was successfully synthesized by using laterite nickel slag as silica and NaAlO2as aluminum sources through the combination of alkali fusion followed by hydrothermal treatment. Then, high performance and low-cost microporous13X zeolite was successfully synthesized by using laterite nickel slag as silica and low-cost material(bauxite) as aluminum sources through the method of alkali fusion followed by hydrothermal treatment. The effects of various factors such as the molar ratio of SiO2/Al2O3, H2O/Na2O, Na2O/SiO2, aging time and crystallization time were investigated. The optimum synthesis conditions of single4A zeolite and13X zeolite were fully characterized by X-ray diffraction. Meanwhile, the crystalline change laws of other zeolites (NaP、Sodalite) were also discussed.The optimum synthesis conditions of single4A zeolite and13X zeolite were as follows:Zeolite4A:n(H2O/Na2O)=110, n(SiO2/Al2O3)=2, n(Na2O/SiO2)=1.4, crystallization time is8h.Zeolite13X:n(H2O/Na2O)=40,(SiO2/Al2O3)=3.2, n(Na2O/SiO2)=1.6, aging time is24h, crystallization time is6h.Secondly, the zeolites synthesized at the optimal conditions were fully characterized by themogravimetry, chemical analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and N2adsorption-desorption measurement at77K.Finally, the adsorption capacities of synthesized4A zeolite and13X zeolite for CO2, N2at30℃and60℃under normal pressure using TGA were also studied in this study. The adsorption capacities of4A zeolite for CO2and N2at30℃are3.803mmol/g and0.389mmol/g, respectively. The adsorption capacities of4A zeolite for CO2and N2at60℃are2.939mmol/g and0.964mmol/g, respectively. The adsorption capacities of13X zeolite for CO2and N2at30℃is2.225mmol/g and1.671mmol/g. The adsorption capacities of13X zeolite for CO2and N2at60℃are2.225mmol/g and1.671mmol/g, respectively. The results show that the synthesized4A zeolite and13X zeolite has high adsorption selectivity over CO2/N2at30℃, which can be used as good adsorbents for CO2/N2separation. And as the temperature is increasing, the adsorption selectivity of CO2/N2on as-synthesized zeolites would decrease.