| Ionic liquid(IL),a special group of molten salts,is composed of cations and anions.The development and industrial applications of ILs will eventually lead to their release into the aquatic environment,resulting in contamination.An increasing number of toxicity studies have shown that many commonly used ILs are toxic in nature,which will bring threat to human health and ecological impacts.Therefore,the growing applications and potential risks of ILs call for the development of effective treatment technologies for their removal from the aquatic systems.Adsorption is one of the most efficient and cost-effective techniques for IL removal.Recently,the ordered porous material have received increasing attention as the excellent adsorbents owing to their distinctive properties such as a large specific surface area and regularly shaped inner channel.Therefore,it is necessary to study the structure-activity relationship between the properties of ordered porous materials(eg.pore framework and surface chemistry)and the adsorption behavior of ionic liquids and to reveal the main mechanism controlling ILs' adsorption,which will provide a theoretical basis and technical support for the development of cost-effective adsorbents for IL removal.This paper systemed studied the adsorption behavior of imidazole-based ionic liquids([Cimim][Cl],[C4mim][Cl],[C8mim][Cl]and[C16mim][Cl])contaminants on ordered porous materials(zeolites,oxidized ordered mesoporous carbon,metal-organic framework material MIL-101(Cr)-SO3H and zeolite template carbon ZTC).Simultaneously,the influence of physicochemical properties of imidazole-based ionic liquids and the elemental composition,surface chemical properties,pore structure and pore size distribution of the porous materials were also investigated.The main conclusions of each chapter are as follows:(1)The adsorption behavior of imidazole-based ionic liquids on zeolites was systematically studied.It was found that the pore structure and pore size distribution of zeolites had a significant effect on the adsorption of imidazole-based ionic liquids,which was mainly achieved by pore-filling effects;Both the framework aluminum content and the location of aluminum atom determined the adsorption behavior of the ionic liquids on the aluminum-containing zeolites;The ionic liquid cation played an important role on its adsorption to zeolites,and the influence of anion species was negligible;Ionic liquids are preferentially adsorbed on high-aluminum-containing zeolites by ion exchange,while long chain substituent ionic liquids are preferentially adsorbed at low-aluminum-containing zeolites by hydrophobic partition and pore-filling effect.(2)This study indicated that the channel difference had a significant effect on the oxidation efficiency of porous carbon-based adsorbents;Due to its open and regular-shaped pore structure,the inner surface of OMC was fully accessible for nitric acid,giving rise to effective modification,while the oxidation of AC was less efficient than OMC owing to the closed and irregular-shaped microporous structure of AC;Surface oxidation markedly enhanced IL adsorption by both OMC and AC and the oxidized OMC had a substantially higher adsorption capacity than oxidized AC;IL adsorption on oxidized OMC was predominantly governed by ion exchange.(3)This study reported that the MIL-101(Cr)-SO3H with sulfonic acid functional groups had an ultra-high adsorption capacity for imidazolium-based ionic liquids;The adsorption capacity of[C4mim][Cl]by MIL-101(Cr)-SO3H was much higher than that of MIL-101(Cr)without functional groups.It is mainly due to that the sulfonic acid functional group(-SO3H)facilitated the adsorption of ionic liquid through ion exchange mechanism;Compared to anionic species,the cation size of the imidazole-based ionic liquid had a more importamt impact on its adsorption to MIL-101(Cr)-SO3H.(4)This study reported an efficient adsorbent(zeolite templated carbon,ZTC)for the adsorption removal of long-chain substituent imidazole-based ionic liquids for the first time;Commercial activated carbon exhibited higher adsorption capacity to the short-chain substituent ionic liquids([C4mim][Cl]and[C8mim][Cl])due to the micropore-filling effect;ZTC exhibited superior adsorption capacity for long alkyl-chain IL[C16mim][Cl]due to its open,regular-shaped and interconnected pore structure;The pore structure of ZTC was also conducive to the rapid diffusion of[C16mim][Cl]in its inner pores,thereby shortening the equilibrium time for adsorption of[C16mim][Cl];ZTC could be regenerated with ethyl alcohol and displayed stable adsorption behavior within ten consecutive adsorption-regeneration cycles. |
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