Efficient removal of p-nitrophenol from water by imidazolium ionic liquids functionalized cellulose microsphere

Removing p-nitrophenol (PNP) from water resources is crucial due to its significant threat to the environment and human health. Herein, imidazolium ionic liquids with short/long alkyl chain ([C₂VIm]Br and [C₈VIm]Br) modified cellulose microspheres (MCC-[C₂VIm]Br and MCC-[C₈VIm]Br) were synthesized by radiation method. To examine the impact of adsorbent hydrophilicity on adsorption performance, batch and column experiments were conducted for PNP adsorption. The MCC-[C₂VIm]Br and MCC-[C₈VIm]Br, with an equivalent molar import amount of ionic liquids, exhibited maximum adsorption capacities of 190.84 mg/g and 191.20 mg/g for PNP, respectively, and the adsorption equilibrium was reached within 30 min. Both adsorbents displayed exceptional reusability. Integrating the findings from XPS and FTIR analyses, and AgNO₃ identification, the suggested adsorption mechanism posited that the adsorbents engaged with PNP through ion exchange, hydrogen bonds and π-π stacking. Remarkably, the hydrophobic MCC-[C₈VIm]Br exhibited superior selectivity for PNP than the hydrophilic MCC-[C₂VIm]Br, while had little effect on adsorption capacity and rate. MCC-[C₈VIm]Br-2 with high grafting yield increased the adsorption capacity to 327.87 mg/g. Moreover, MCC-[C₈VIm]Br-2 demonstrated efficient PNP removal from various real water samples, and column experiments illustrated its selective capture of PNP from groundwater. The promising adsorption performance indicates that MCC-[C₈VIm]Br-2 holds potential for PNP removal from wastewater.