Biochar from Wood Chips and Corn Cobs for Adsorption of Thioflavin T and Erythrosine B

Biochars from wood chips (WC) and corn cobs (CC) were prepared by slow pyrolysis and used for sorption separation of erythrosine B (EB) and thioflavin T (TT) in batch experiments. Biochar-based adsorbents were extensively characterized using FTIR, XRD, SEM-EDX, and XPS techniques. The kinetics studies revealed that adsorption on external surfaces was the rate-limiting step for the removal of TT on both WC and CC biochar, while intraparticle diffusion was the rate-limiting step for the adsorption of EB. Maximal experimental adsorption capacities Q(maxexp) of TT reached 182 +/- 5 (WC) and 45 +/- 2 mg g(-1) (CC), and EB 12.7 +/- 0.9 (WC) and 1.5 +/- 0.4 mg g(-1) (CC), respectively, thereby indicating a higher affinity of biochars for TT. The adsorption mechanism was found to be associated with pi-pi interaction, hydrogen bonding, and pore filling. Application of the innovative dynamic approach based on fast-field-cycling NMR relaxometry indicates that variations in the retention of water-soluble dyes could be explained by distinct water dynamics in the porous structures of WC and CC. The obtained results suggest that studied biochars will be more effective in adsorbing of cationic than anionic dyes from contaminated effluents.

Automated summary

Biochars derived from wood chips and corn cobs were studied for their adsorption behavior towards erythrosine B and thioflavin T. The results showed that biochars had a higher affinity for thioflavin T, and the adsorption mechanism involved pi-pi interaction, hydrogen bonding, and pore filling. The use of fast-field-cycling NMR relaxometry revealed distinct water dynamics in the porous structures of the biochars, which explained the variations in the retention of water-soluble dyes.