Synthesis Of Imidazolium Ionic Liquid-modified Silica For Adsorption Of 2,4-Dinitrophenol

Phenolic compounds are discharged in the wastewater streams of various industries such as metal casting, pulp and paper manufacturing and so on. These compounds are harmful to organisms at low concentrations, many of them have been classified as hazardous pollutants, and some chlorophenols and nitrophenols are even known to possess carcinogenic and immunosuppressive properties. Therefore, removal of phenolic pollutants from aqueous solutions is necessary for environment protection and has been investigated by various methods. Among the numerous methods, adsorption method is very effective and is still constantly investigated and developed due to its low initial cost, simplicity of design and ease of operation. In this paper, six novel imidazolium ionic liquids-modified silica adsorbents were synthesized and used for removal of phenols from aqueous solutions. The adsorption properties of these materials towards 2,4-dinitrophenol were investigated.This paper is consist of five chapters.In chapter 1, the harm of phenolic pollutants, the features and classification of ionic liquid, the advantages of supported ionic liquid were summarized. The main applications and achievements of supported ionic liquids in catalytic reactions, surface modification, separation technologies(include SPE, LC, GC CEC and gas capture) and electrochemistry were overviewed.In chapter 2, porous silica was chemically modified with a series of imidazolium ionic liquids by taking 3-(chloropropyl)triethoxysilane as the silane coupling agent. So, six kinds of ionic liquid-modified silica adsorbents have been prepared. Three of the new adsorbents called monomeric adsorbents were obtained via monomeric immobilization of imidazolium ionic liquids on the surface of silica, the remaining three adsorbents called cooperative adsorbents were prepared by co-immobilization of two imidazolium ionic liquids on the surface of silica, respectively. Subsequently, the materials were characterized and identified by various techniques such as FT-IR, TGA, N2 adsorption-desorption isotherm, and element analysis. The analysis results showed that imidazolium ionic liquids-modified silica adsorbents were synthesized successfully with good thermal stability, and the frameworks and ordered porous structures of the silica were kept well.In chapter 3 and chapter 4, firstly, several kinds of phenolic compounds were used as adsorbates to investigate the selectivity of the six adsorbents and their adsorption capacities of 2,4-dinitrophenol were far higher than other compounds. Therefore, 2,4-dinitrophenol was used to investigate the adsorption behaviors of the six adsorbents. Batch and column method were used to study the adsorption properties of monomeric and cooperative adsorbents towards 2,4-dinitrophenol in aqueous solution. To obtain the optimum condition, different variables such as adsorbent dose, temperature and pH were studied, and the optimum conditions were found to be 25 mg/50 mL, 30 °C and pH of 4.0, respectively. The maximum adsorption capacity of SilprBImCl,SilprNImCl,SilprAImCl,SilprDBImCl,SilprDAImCl and SilprBAImCl were 61.3 mg/g、67.0 mg/g、64.5 mg/g、83.1 mg/g、40.3 mg/g and 49.2 mg/g, respectively. The existence of anion such as Cl- and NO3- in the solution had obvious inhibitory effect on the adsorption behavior, and with the increase of anion concentration, the adsorption capacity decreased. The Langmuir model was applied to fit the experimental equilibrium data for the six adsorbents and adsorption kinetics suggested that the adsorption process onto SilprBImCl was followed the pseudo-second-order kinetic model.The adsorption-elution experiments indicated that 2,4-dinitrophenol can be removed from aqueous solutions by adsorbents packed columns and each of the maximum recovery was above 98%. The imidazolium ionic liquids-modified silica adsorbents were regenerated and reused fifteen times by washings with HCl and water in turn without obvious loss in the concentration separation capacity.In chapter 5, a conclusion was obtained that this experiment has a certain research significance for the separation and determination of phenolic compounds, and the six kinds of adsorbents we have synthesized can be used to separation and enrichment of 2,4-dinitrophenol of aqueous solutions.