Carbonized Leather Waste: A Review and Conductivity Outlook

Abstract

The carbonization of collagen-based leather waste to nitrogen-containing carbon is reviewed with respect to the preparation, characterization of carbonized products, and applications proposed in the literature. The resulting nitrogen-containing carbons with fibrous morphology have been used as adsorbents in water pollution treatment, in electrocatalysis, and especially in electrodes of energy-storage devices, such as supercapacitors and batteries. Although electrical conductivity has been implicitly exploited in many cases, the quantitative determination of this parameter has been addressed in the literature only marginally. In this report, attention has been newly paid to the determination of conductivity and its dependence on carbonization temperature. The resulting powders cannot be compressed into pellets for routine conductivity determination. A new method has been used to follow the resistivity of powders as a function of pressure up to 10 MPa. The conductivity at this pressure increased from 9.4 × 10−8 S cm−1 for carbonization at 500 °C to 5.3 S cm−1 at 1000 °C. The conductivity of the last sample was comparable with conducting polymers such as polypyrrole. The carbonized leather thus has the potential to be used in applications requiring electrical conduction.

Carbonized Leather Waste with Deposited Polypyrrole Nanotubes: Conductivity and Dye Adsorption

“…Carbonized leather has a resistivity of the same order of magnitude as globular polypyrrole [12], and the same applies for their composites (Figure 5a). The analogous…”

“…Carbonized leather has a resistivity of the same order of magnitude as globular polypyrrole [12], and the same applies for their composites (Figure 5a). The analogous samples with polypyrrole nanotubes are more conducting, their resistivity being lower by approximately one order of magnitude (Figure 5b).…”

“…The carbonized leather wastes have been applied mainly for the adsorption of a cationic dye, methylene blue (Basic Blue 9) [10,[51][52][53][54][55][56]. The adsorption of methyl orange (Acid Orange 52) has only been reported seldom [1,12] and was found to be better compared with methylene blue. All papers report the dye adsorption but quantitative comparison is not possible due to the variations in concentrations of dyes and adsorbents and the general experiment design.…”

“…Carbonization of leather waste to a fibrous conducting nitrogen-containing biochar, i.e., a waste to useful material, has been reported [10][11][12]. Applications involving this type of biochar concern dye adsorbents [13,14], removal of harmful chromium(VI) from wastewater [15,16], electromagnetic radiation shielding [11], supercapacitor electrodes [17,18], batteries [19,20] or fuels [21,22].…”

“…Such composites could be compressed to solid materials with applicable mechanical integrity and may benefit from the similar or complementary properties of both components (Table 1). [8,[10][11][12][13][14].…”