Functionalization of lignocellulosic based fibers for enhanced and sustainable wastewater pollutant removal

Abstract

Clean water scarcity and the increasing burden of anthropogenic pollutants demand efficient and recyclable sorbent materials. Here, kenaf fibers (KF) and dwarf palm fibers (DPF) are reported as lignocellulosic platforms for multifunctional pollutant removal, showing enhanced performance through the grafting of a fluorinated 1,2,4-oxadiazole pendant (FOX). FOX functionalization of fibers is achieved under mild conditions via nucleophilic aromatic substitution. The success of functionalization is confirmed via FTIR/ATR, showing the presence of FOX peculiar bands; SEM-EDX assessing fluorine content of FOX-fibers as well as different morphology compared to pristine ones and DSC and TGA analysis, indicating different thermal behavior between functionalized and pristine fibers. The adsorption performance of pristine and FOX-fibers is investigated using two model dyes, rhodamine B (RhB) and Acridine Orange (AcrO); moreover, silicone oil has been used as a model hydrophobic contaminant. Pristine and FOX-fibers show appreciable dye uptake with 100% AcrO removal after 24 h. Interestingly, FOX-KF fibers exhibit notably enhanced RhB adsorption, increasing from 44% removal for KF to 73% for FOX-KF after 24 h. Oil sorption capacities increase as well for FOX-fibers with respect to pristine ones (from 1.15 g g⁻¹ for DPF to 5.00 g g⁻¹ for FOX-DPF, and from 6.21 g g⁻¹ for KF to 7.25 g g⁻¹ for FOX-KF). Both FOX-DPF and FOX-KF maintained their sorption capacity over at least five adsorption–desorption cycles, with efficient recovery of both oil and hexane used as washing solvents. Overall, FOX-KF and FOX-DPF emerge as renewable, robust and recyclable sorbents for hydrophobic pollutant remediation in wastewater.