| Popis: |
We report an improved absorbent material for NO x , a major component of acid rain and other environmentally hazardous chemicals. This new material is based on the hydrotalcite-like compounds and incorporating Mg and Zn markedly enhances the capacity of adsorbing NO x . Ni/Al, Mg/Ni/Al, and Zn/Mg/Ni/Al hydrotalcite-like compounds were synthesized by coprecipitation, characterized by X-ray diffraction (XRD), ICP, infrared (IR), and scanning electron microscopy (SEM) and tested for the performance in adsorption of NO x on derived mixed oxides. The prepared adsorbents give better performance than the conventional activated carbons. The adsorption capacity for NO x is highly dependent on the composition of adsorbent materials. The capacity is highest for Zn 1 Mg 1 Ni 1 Al 1 at 2300 mg/g, with 73% efficiency. The physical and structural properties of the materials before and after NO x adsorption were investigated to gain a better understanding of the underlying mechanism. IR d-spacing and SEM measurements indicate that physisorption and chemisorption have occurred cooperatively. Adsorption of NO x has led to the reformation of layered double structure by the resultant nitrates and nitrites around the oxide sites between the positively charged layers of the hydrotalcite. As a consequence, it catalyses more and more NO x to be absorbed. Other possible mechanisms are also discussed. |
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