Superadsorbent hydrogel based on lignin and montmorillonite for Cu(II) ions removal from aqueous solution

Superadsorbent hydrogel was prepared from lignin and montmorillonite for Cu(II) ions removal, and the chemical structure and morphology of the hydrogel were characterized by FT-IR, XRD, SEM and XPS. The swelling kinetics of the prepared hydrogel was investigated, and the result showed that the swelling process fit the Schott second-order dynamic equation. The influences of pH, contact time, Na⁺ concentration, and initial Cu(II) ion concentration on adsorption were studied, and the maximum adsorption value was 1.17 mmol/g, and the adsorption was rapid during the initial 5 h period, and copper ions adsorption on the superadsorbent hydrogel is a favorable process. The results also indicated that the adsorption kinetics was in accordance with the pseudo-second-order kinetic model and the adsorption isotherm conformed to the Freundlich model. FT-IR and XPS analysis revealed that the adsorption behavior was mainly due to ion exchange. The desorption ratios of copper ions from the superadsorbent were >0.8, and the regeneration efficiency was >80% after five cycles reuse, and the results show the excellent desorption performance and reusability of the prepared hydrogel.