Experimental and DFT Investigation of Crystal Violet Biosorption by Taraxacum officinale Leaf Biomass

Leaf powder obtained from wild Taraxacum officinale was directly used as a biosorbent for the removal of Crystal Violet (CV), a widely used cationic dye, because the leaves are rich in fibers and minerals and have not previously been employed in their untreated form for biosorption. Standard instrumental analyses were employed for the identification of surface functional groups (FT-IR), imaging of surface morphology (FE-SEM), and elemental characterization (EDX). Adsorption was favored under alkaline conditions, reaching a maximum removal efficiency of 46.53% at pH 12, corresponding to an experimental adsorption capacity of 149.1 mg g–1, while adsorbent dosages between 100 and 200 mg were effective for dye removal. The untreated biomass surface exhibited adsorption-favoring grooves and stomata. Taraxacum officinale biomass exhibited a lignocellulosic structure, with carbon and oxygen contents of 54.26 and 42.46 at%, respectively. Adsorption equilibrium was best described by the nonlinear Langmuir model (R2 = 0.948), supporting monolayer adsorption onto a relatively homogeneous surface. The D–R model further supported a physicochemical adsorption mechanism. Frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses were performed at the B3LYP/6-311++G** level in both gas and aqueous media to elucidate the electronic interactions between CV and the lignocellulosic surface.