The Potential of Almond Skin as a Sustainable Biomaterial for Eliminating Azo Dye in Aqueous Media

The production and consumption of almonds occur in several locations worldwide, yielding immense volumes of trash, mainly skin. The current study evaluated the adsorptive manners of almond skin (AS) without modification for clearing Basic Red 46 dye (BR46) from water. XRD, FTIR, SEM/EDX, BET, and pH_pzc are among the many analytical tools used to investigate AS’s surface features. BR46 adsorption over AS was efficient at pH 8 and 2 g/L of AS, conferring 57.45 mg.g⁻¹ within 120 min. The Langmuir was seen to accurately present the equilibrium curves, exhibiting q_max = 66.90 mg.g⁻¹, whereas the PSO model precisely resembled the empirical results. The thermodynamic results proclaimed that BR46 adsorption was favorable, with spontaneity (ΔG° < 0) and endothermicity ΔH° (5.03 kJ.mol⁻¹). Further, the AS reusability prospect was investigated, revealing excellent regeneration potential even after 4 adsorption/desorption runs. These findings suggest the potential of valorizing almond skin as a sustainable resource, which could be a promising prospect for environmental remediation.