A New Solid Adsorbent for CO2 Capture Based on an Amine Polycarboxylate Ionic Liquid with Multiple Absorption Sites

In this study, an amine polycarboxylate ionic liquid with multiple absorption sites, named [P4442]2[IDA], was selected to synthesize a new type of solid adsorbent for CO2 capture with a modified clay mineral AT (attapulgite). A series of experiments of the synthesized adsorbents were performed using a TGA instrument at atmospheric pressure. Different [P4442]2[IDA] loadings and temperatures were evaluated in the CO2 adsorption process, and the maximal amount of CO2 adsorbed on the adsorbent was 1.531 mmol/g with [P4442]2[IDA] loading of 30% at a temperature of 303 K. Note that, after the [P4442]2[IDA] molecules were impregnated onto the modified AT carrier, the utilization efficiency of [P4442]2[IDA] increased nearly three times, compared with pure [P4442]2[IDA]; this result also indicates that the cost of CO2 capture by ionic liquid is reduced by this method. Moreover, multiple analysis methods were used to analyze the composition and the structure of the adsorbent. The experimental data obtained from the CO2 adsorption process were fitted by two different isotherm models and three different kinetic models; the excellent fit of the Freundlich isotherm model and Avrami's kinetic model indicates that CO2 capture by this adsorbent is the process which dominated by chemical adsorption and coexists with physical adsorption. In addition, the amount of CO2 adsorbed was only little slightly reduced after ten cycles, exhibiting excellent cyclic adsorption performance which is due to the stability of the bond between the [P4442]2[IDA] molecules and the modified AT carrier, as well as the extremely low volatility of the ionic liquid.