Systematic evaluation of cellulose nanowhiskers effect on the Pb(II) adsorption by superabsorbent hydrogels nanocomposites: An experimental and theoretical study

Abstract

Abstract The incorporation of cellulose nanowhiskers (CNWs) in superabsorbent hydrogels of starch grafted with poly(acrylic acid) (ST-g-PAAc) is proposed as a strategy to obtain adsorbent materials with superior performance for Pb(II) removal. The functionalized surface of CNWs provides additional interaction sites, contributing to the high adsorption capacity (935.8 mg/g) of the composite hydrogel. The presence of CNWs also minimizes the effects of temperature and competition with other ions, making the adsorption process more stable and efficient. Density functional theory (DFT) calculations revealed that the hydroxyl groups of CNWs play a crucial role in providing additional binding energies (approximately 30 kcal/mol) for the Pb(II) ions, favoring the spontaneity and kinetics of the adsorption process. The adsorption process on the CNWs-containing hydrogel involves chemisorption and intra-particle diffusion, indicating multiple steps occurring during the adsorption of Pb(II) ions. Also, the CNWs-containing hydrogel demonstrates excellent reusability, showing minimal loss of adsorption capacity after consecutive reuses. This characteristic makes the composite highly attractive for practical applications in real-world scenarios. In short, the systematic evaluation of different experimental conditions has confirmed the superior adsorption performance of the composite hydrogel and gives light on the role of CNWs as a valuable nanofiller to enhance the adsorption properties of these materials.