Deep eutectic solvent-assisted dual valorization of waste distillers' grain-derived lignocellulose: pyrolyzed hydrochar microflower-supported peroxymonosulfate activation and lignin carbon dot-aided Fe3+ detection

Abstract

Multifaceted valorization of lignocellulose into advanced environmental functional materials is of considerable relevance for a carbon efficient circular economy. In this study, a tailored multi-scale engineering approach assisted by AlCl₃·6H₂O/glycerol deep eutectic solvent (DES) fractionation was presented for the dual valorization of waste distillers' grain-derived lignocellulose. This approach allowed for the production of cellulose-derived pyrolyzed hydrochar microflowers (PHMs) and lignin-derived carbon dots (LCDs) for multiphase control of water pollutants. The PHMs exhibited a well-defined flower-like morphology with a large surface area (662 m² g⁻¹) and a highly open porous structure. Rich active centers (Co–N_x, graphitic N, and Co⁰ species) make them a robust heterogeneous peroxymonosulfate (PMS) activator for the removal of antibiotics with great adaptability. Notably, the integration of PHM membrane filtration with PMS activation achieved an impressive average tetracycline removal of 93.2% over 30 cycles at a high permeate flux of 257.96 L m⁻² h⁻¹, highlighting the membrane's suitability for industrial applications. Additionally, the excellent optical properties, photostability, and hydrophilicity of LCDs open the door for detecting Fe³⁺ from 10–150 μM, exhibiting a linear standard curve with a high correlation coefficient (R² = 0.96). The proposed integrated technique platform enables the comprehensive upgrading of lignocellulosic biomass and provides advanced carbon materials for downstream wastewater restoration towards industrially relevant processes.