Research on the adsorption property of supported ionic liquids for ferulic acid, caffeic acid and salicylic acid

In this paper, the preparation of new supported ionic liquids (SILs) composed of the N-methylimidazolium cation and the quinoline cation is described. They have been confirmed and evaluated by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Six kinds of different SILs included SiO2·Im+·Cl−, SiO2·Im+·BF4−, SiO2·Im+·PF6−, SiO2·Qu+·Cl−, SiO2·Qu+·BF4− and SiO2·Qu+·PF6−. The adsorption characteristics of ferulic acid (FA), caffeic acid (CA) and salicylic acid (SA) on SILs were investigated by static adsorption experiments. It was found that SiO2·Qu+·Cl− had excellent adsorption and desorption capacity to three tested phenolic compounds. The dynamic adsorption characteristics of FA, CA and SA on SiO2·Qu+·Cl− were also studied. The saturated adsorption capacity of FA, CA and SA using SiO2·Qu+·Cl− as adsorbent was 64.6 mg/g, 53.2 mg/g and 72.2 mg/g respectively. Using 70% ethanol as eluent, the saturated desorption efficiencies of FA, CA and SA were 97.2%, 90.3% and 96.5% respectively. Thus, SiO2·Qu+·Cl− had strong adsorption and separation capacity for FA, CA and SA.