Sorption of textile azo dyes by Miscanthus × giganteus and characterization of the interaction.

Miscanthus × giganteus was tested for textile dye removal. Sorption of Direct Blue 78 was achieved slowly by the leaf (63% after 24 h), while sorption of Basic Red 18 was fast by the stem (96% in an hour). Lignocellulose (24.62% in leaf, 41.34% in fresh and 48.05% in old stem) was responsible for the interaction. FTIR spectra and SEM images of native material and with sorbed dye were similar. Negligible quantities of peroxidases (2 μg/g in old stem) pointed to physical forces underlying sorption. pHpzc for stem-BR18 pair was 5.90 and maximum sorption could be achieved in pH interval 4-9. Desorption and repeated sorption defined maximal binding capacity of 20.8 mg BR18/g of stem. BR18 could be desorbed by only 23% with 0.1 M HCl. Small quantities of zinc (0.71-1.13%), copper (0.74-1.43%) and silicon (0.12-0.28%) were detected without significant difference between samples, as well as chlorine (0.24%) in the sample after desorption and in the sample with sorbed 20.8 mg/g BR18. We propose a more thorough investigation of M. × giganteus as a sorbent of a wider pallet of dyes, as it exerts a potential for such purpose.