Grafting of reactive dyes onto lignocellulosic material: Application for Pb(II) adsorption and electrochemical detection in aqueous solution

Triplochyton scleroxylon (Ayous) sawdust was modified by grafting two reactive dyes (Reactive Red 120 (RR120) and Reactive Black 5 (RB5)) inspired by the strategy used for cellulosic fibers dyeing. The visual appearance as well as the infrared spectra and the point of zero charge determination confirm the effective attachment of the dyes onto sawdust. The anionic charges resulting from the grafted dyes were exploited for Pb(II) biosorption and electrochemical detection in aqueous solution. The presence of dyes grafted onto Ayous sawdust (SA) greatly improves its affinity for Pb(II) biosorption as confirmed by the increase of the pseudo-second order kinetic rate constant, especially in the case of RR120 modified sawdust (SA-RR120). Moreover, the maximum adsorption capacities obtained from the Langmuir model (207 µmol g−1, 281 µmol g−1 and 298 µmol g−1 respectively for SA, SA-RB5 and SA-RR120) confirmed the improvement in adsorption resulting from sawdust dyeing. Used as glassy carbon electrode (GC) modifiers, the functionalized sawdust improved the electrochemical detection of Pb(II). After optimization of the experimental parameters, sub-nanomolar detection limits were obtained (1.3 nM, 0.7 nM and 0.4 nM for GC/SA, GC/SA-RB5 and GC/SA-RR120 respectively). In addition to such improvements in Pb(II) biosorption and trace-level detection, these materials also showed appreciable selectivity and excellent performance in real media samples. [Display omitted] •Effective covalent grafting of reactive dyes onto sawdust.•Improvement of Pb(II) biosorption using dyed sawdusts.•Improvement of Pb(II) detection using dyed sawdust modified electrodes.