Title
Lignin valorisation for the adsorption of Mo(VI) ions from contaminated media: a sustainable and eco-friendly approach
Authors
ELENA UNGUREANU, BOGDAN-MARIAN TOFĂNICĂ, CARMEN O. BREZULEANU, COSTEL SAMUIL, OVIDIU C. UNGUREANU, MARIA E. FORTUNĂ, RĂZVAN ROTARU, STEJĂREL BREZULEANU and VALENTIN I. POPA

Received January 16, 2026
Published Volume 60 Issue 5-6 May-June
Keywords Mo(VI) ions, lignin, contaminated media, Brassica oleracea L., adsorption

Abstract
Lignin has a three-dimensional amorphous network structure and hydrophilic functional groups, which make it suitable for the removal of Mo(VI) ions from contaminated aqueous environments. The optimal adsorption conditions were previously established by performing a series of experiments. These experiments targeted the mass of lignin (the adsorbent), the concentrations of Mo(VI) in aqueous environments, the initial pH of the aqueous solution of molybdenum and lignin, and the interphase contact time. In this work, Sarkanda grass lignin was evaluated as an adsorption material for Mo(VI) through a series of characterization analyses, including energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG) and derivative-thermogravimetric (DTG) analyses. The state of chemical equilibrium was described by evaluating several thermodynamic parameters, including enthalpy, entropy, Gibbs free energy, and experimental adsorption isotherms. These parameters were interpreted using the Freundlich and Langmuir models. The kinetics of the process were explained by applying the Lagergren I and Ho-McKay II mathematical models. The assessment of biostability was conducted through the implementation of germination tests on white cabbage seeds (late variety – Brassica oleracea L. var. Capitata alba). These seeds were introduced into lignin that had been contaminated with Mo(VI), and the filtrates resulting from phase isolation were also examined. The data obtained suggest the potential application of Sarkanda grass lignin in the adsorption of Mo(VI) from aqueous media within the established experimental parameters. This analysis underscores several salient advantages, including the favorable mass ratio and interphase time, a straightforward working technique, the abundance and regenerability of the resource, its economic viability, and its biocompatibility.