Effect of Heavy Metal (Zn) on Redox Property of Hydrochar Produced from Lignin, Cellulose, and d-Xylose

Abstract

To provide fundamental information for environmentally sound utilization of hyperaccumulator, hydrothermal carbonization (HTC) of Zn-loaded lignin, cellulose, and D-xylose was carried out to explore the effect of Zn(II) on chemical structure and the redox property of hydrochar. By batch redox reaction as well as I 2 /NaBH 4 titration, we quantified the reducing and oxidizing capacities of three kinds of hydrochar. Results indicated that all hydrochar samples are redox-active with a reducing ability that is more extensive than the oxidizing ability. Reducing capacities of hydrochar (by I 2 titration) are in the order of lignin (1.021 mmol e − /g) ≫ cellulose (0.300 mmol e − /g) > D-xylose (0.142 mmol e − /g). Zn(II) loading increases the reducing capacities of lignin (up to 3.340 mmol e − /g) and cellulose (up to 1.089 mmol e − /g) hydrochar while it decreases the reducing capacity of D-xylose hydrochar. Redox ability is highly correlated with surface phenolic hydroxyl/benzoquinonyl groups of hydrochar. We propose that Zn(II) affects the redox ability of hydrochar by inhibiting the decomposition of phenolic hydroxyl group during hydrothermal carbonization of biomass.

Effect of Pyrolysis Temperature on Acidic Oxygen-Containing Functional Groups and Electron Storage Capacities of Pyrolyzed Hydrochars

“…While the data suggest cellulose contributed to the ESCs of wood pyrolyzed hydrochars, the fact that cellulose pyrolyzed hydrochars possessed lower ESCs than wood pyrolyzed hydrochars for the same pyrolysis temperature (Figure ) indicates that other wood components (e.g., lignin) contributed more than cellulose to the total ESCs of wood pyrolyzed hydrochars on the mass basis. It has been suggested that lignin-derived chars possessed twice the number of (hydro)­quinoic functional groups than cellulose- and d -xylose-derived chars, which is consistent with the observation from this study.…”

Hydrochar-Facilitated Anaerobic Digestion: Evidence for Direct Interspecies Electron Transfer Mediated through Surface Oxygen-Containing Functional Groups

“…However, PH had higher peaks for the redox property compared to the other hydrochars, while it did not promote methane production. The redox properties of hydrochar were further quantified by I 2 /NaBH 4 titration (Figure 5b), 17 and PH still had the highest redox capacity considering the highest electron donating capacity (EDC) and electron accepting capacity (EAC), which was consistent with cyclic voltammetry (CV) results. It seems that the redox properties of hydrochar were also not correlated to the enhancement of the methane production rate.…”

“…However, a detailed mechanism is still unknown, especially from the microbial aspects. Although there is still no literature reporting the conductivity of hydrochar, it is known that hydrochar has redox-active properties . Previous studies showed that biochar could facilitate DIET for microbial reduction of ferrihydrite and methanogenesis due to its redox-active properties. , Therefore, it was hypothesized that hydrochar could promote methanogenesis through DIET.…”

A renewable biomass-based lignin film as an effective protective layer to stabilize zinc metal anodes for high-performance zinc–iodine batteries

“…Firstly, the formation of stable coordination compounds between phenolic hydroxyl groups within lignin and Zn ions can produce a robust and tight layer on the Zn metal surface. 26 Secondly, oxygen-containing functional groups within lignin can also coordinate with empty orbitals within Zn metal to form coordinate bonds, 27 which can improve the adhesive forces on the surface of Zn metal. Lastly, lignin coated lms play a role as a block layer to homogenize the interfacial Zn 2+ ux and suppress the formation of Zn dendrites and the corrosion of I 3 À ions.…”