Adsorption mechanism of nitrate on cotton template Zn/Ti/Fe layered double oxide in water

doi:10.11949/j.issn.0438-1157.20180839

Abstract

Abstract:

The cotton template Zn/Ti/Fe layered double oxide (YLDO) and Zn/Ti/Fe layered double oxide (NLDO) were prepared by coprecipitation-baking method. The adsorbents were characterized by SEM, N₂ adsorption, FTIR and XRD. The adsorption mechanism of nitrate on YLDO and NLDO in water and the regeneration mechanism of ultraviolet photocatalytic were investigated. The results showed that using cotton as template, the specific surface area of YLDO increased to 74.8 m²·g^-1, and the number of large pores increased. The C element is introduced into the chemical composition, which enhances the adsorption capacity. The magnetic materials are composed to magnetic separation. The equilibrium adsorption capacity of YLDO is 66.57 mg·g^-1 at 298 K and pH of 7, which is 22.6% higher than that of NLDO. The adsorption isotherms of nitrate on YLDO and NLDO can be described better with Langmuir equation model than Freundlich model, and the pseudo-second-order kinetics equation fit well with the adsorption data. The adsorption process for nitrate on YLDO and NLDO are exothermic and spontaneous. The saturated YLDO and NLDO can be regenerated under ultraviolet light, which keep high adsorption capacity after five cycles for continuous adsorption and regeneration. YLDO can effectively remove nitrate from water by adsorption-magnetic separation-ultraviolet photocatalytic regeneration process without secondary pollution and has potential application prospects in nitrate wastewater treatment.

Key words: layered double oxide, cotton template, nitrate, adsorption, kinetic, thermodynamics, regeneration

摘要：

通过共沉淀-焙烧法制备以棉花为模板的Zn/Ti/Fe焙烧态类水滑石（YLDO）和无棉花模板的Zn/Ti/Fe焙烧态类水滑石（NLDO），运用SEM、N₂吸附法、FTIR和XRD对其进行表征，考察YLDO和NLDO对水中硝酸盐的吸附机制及其紫外光催化再生的机理。结果表明，YLDO在形态中引入棉花的遗迹，比表面积增大为74.8 m²·g^-1，大孔数量增加；在化学成分上引入了C元素，提高了吸附性能；形成磁性物质，可通过磁性分离回收。pH为7、298 K时，YLDO对水中硝酸盐的最大吸附量为66.57 mg·g^-1，比NLDO增加了22.6%。YLDO和NLDO吸附硝酸盐的吸附等温线符合Langmuir方程，吸附动力学可用准二级动力学方程来描述，吸附热力学研究表明吸附过程为自发吸热过程。吸附饱和的YLDO和NLDO可在紫外光照射下再生，5次再生循环后仍保持较高的吸附性能。YLDO可通过吸附-磁分离-紫外光催化再生工艺有效去除水中硝酸盐，不产生二次污染，在硝酸盐废水处理中具有潜在的应用前景。

关键词: 焙烧态类水滑石, 棉花模板, 硝酸盐, 吸附, 动力学, 热力学, 再生

CLC Number:

TB332
X703.1

CHENG Aihua, QIAN Dapeng. Adsorption mechanism of nitrate on cotton template Zn/Ti/Fe layered double oxide in water[J]. CIESC Journal, 2018, 69(12): 5283-5291.

程爱华, 钱大鹏. 棉花模板Zn/Ti/Fe-LDO吸附水中硝酸盐机制[J]. 化工学报, 2018, 69(12): 5283-5291.

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