Lignin ‒ A Promising Strategic Resource for Aqueous Media Contaminated with As(III)

The current study proposes to evaluate the adsorption capacity of Sarkanda grass lignin regarding the retention of As(III) from aqueous media from a thermodynamic, spectral and biological point of view, considering the need for rational use of resources and the danger of the As(III) ion derived from its potentially toxic function. The state of chemical equilibrium was assessed by determining the enthalpy, entropy and Gibbs free energy of adsorption, and the diffusion and retention of the polluting species in the lignin pores were highlighted using scanning electron microscopy (SEM). The biostability was analyzed by means of germination tests applied to barley seeds (Hordeum vulgare L., Amethyst variety) incorporated in the lignin infested with As(III) and in the filtrates collected, after phase separation. The experimental results obtained recommend Sarkanda grass lignin for potential applications in the sorption of polluting species from aqueous environments, in particular As(III), offering a sustainable solution also in terms of the valorization of secondary agricultural products, in the context of the circular bioeconomy.