Insights into the interfacial interaction mechanisms of p-arsanilic acid adsorption on ionic liquid modified porous cellulose

Abstract

Organoarsenic compounds are considered as emerging pollutants since they may decompose into highly toxic arsenate in the environment. The adsorption of organoarsenic compounds by natural polymers has drawn research attention, but the adsorption mechanisms remain largely unexplored. In this study, the sorption interfacial interaction mechanisms of p-arsanilic acid on ionic liquid modified celluloses were investigated systematically by sorption models, spectroscopy analysis techniques, and density functional theory calculations. Adsorption experiments showed that the modified cellulose exhibited high adsorption capacity (216.9 mg/g) and fast adsorption rate (3.21 × 10−3 g mg−1·min−1) toward p-ASA. Adsorption model studies revealed that the adsorption process was multilayer adsorption and dominated by the adsorption onto active site. The effect of environmental factors on p-arsanilic acid removal and spectroscopy analysis manifested that p-arsanilic acid interacted with the adsorbent through hydrogen bonding and π-π interaction to form outer-sphere complexes. Density functional theory calculation and independent gradient model analysis were used to analyze the interfacial interaction mechanisms, results of which showed that hydrogen bonding played the dominant role in the adsorption process and the imidazole group was preferential adsorption site. This work provides a valuable reference for understanding the role of weak force in the adsorption process between organoarsenic and adsorbents.