Wood microchannels with multi-carboxyl groups for selective adsorption of Fe3+ from ionic liquids aqueous solution: Experimental and DFT study

Heavy metal contamination is widely present in the spinning field. Some heavy metal ions such as Fe3+ may accumulate in the coagulation bath using ionic liquids (ILs) as green solvents to prepare regenerated cellulose fibers (RCFs), which seriously affect the performance of RCFs and the subsequent regeneration of ILs. This study proposed a new strategy to selectively adsorb Fe3+ from ILs aqueous solution using carboxyl-functionalized wood microchannel (CW). The CW was optimized by citric acid concentration and reaction time using carboxyl group contents as an indicator. The physic-chemical properties of CW were characterized, and its adsorption performance for Fe3+ was also evaluated in a water system. Furthermore, the adsorption selectivity of CW for Fe3+ and ILs was investigated. The results demonstrate that the CW had a high adsorption ratio for Fe3+ (94.73%), while that for ILs was 4.20%. The selective adsorption mechanism, in which the Fe3+ is mainly separated from ILs aqueous solution by complexation with carboxyl group, was confirmed by FTIR, XPS, MIP, and DFT calculation. Accordingly, this paper may provide a new strategy to selectively adsorb Fe3+ from ILs aqueous solution, thus offering an economical and efficient method for ILs recovery and water purification.