Stabilizing Chromium from Leather Waste in Biochar

Abstract

Disposal of chrome-tanned leather waste provides an environmental challenge, with land-based methods risking leaching of chromium into the environment. We investigate the production of biochar from leather as an alternative means to dispose of leather waste. Chrome-tanned leather is heated at 500–1000 °C in an environment excluding oxygen to form biochar. The char is leached in 1 M HCl for 15 h, and the leachate is analyzed for Cr to confirm that Cr does not leach from char formed at or above 600 °C. The char is analyzed by X-ray absorption spectroscopy (XAS) for chemical state and structure. X-ray absorption near edge structure (XANES) analysis shows that the leather and biochar contain Cr as a mixture of Cr sulfate and Cr carbide, with the proportion of Cr as carbide increasing from 0% for untreated leather to 88% for char formed at 1000 °C. Modeling of the extended X-ray absorption fine structure (EXAFS) spectra shows that the atomic near-range structure is consistent with that of chromium carbide for the high-temperature samples. Biochar produced from chrome-tanned leather waste contains highly dispersed chromium present as a stable, carbide-like structure (provided sufficiently high temperatures are used). This material, rather than being an environmental problem, may be used for soil remediation and carbon sequestration.

High-efficiency adsorption of tetracycline by the prepared waste collagen fiber-derived porous biochar

“…Studies have shown that the formation of Cr carbide does not lead to the leaching of Cr. 50 Leaching of Cr ions was signicantly reduced (C Cr < 0.01 mg L À1 ) when the pH of the experimental condition was neutral. The comprehensive experimental results and actual conditions proved that PBC-800 is very stable at pH > 3.…”

The role of temperature on Cr(VI) formation and reduction during heating of chromium-containing sludge in the presence of CaO

“…The main disposal method for hazardous metals sludge is to stabilize or solidify the solid waste using cement before landfill (Barbir et al, 2012;Swarnalatha et al, 2006Swarnalatha et al, , 2008Wells et al, 2014). However, large amounts of cementitious material are required to produce solidified waste that is strong enough to prevent the leaching of hazardous metals from broken products, and this increases the volume of cement required for landfill (Filibeli et al, 2000;Swarnalatha et al, 2006Swarnalatha et al, , 2008.…”

Research progress on resource utilization of leather solid waste

“…However, toxic Cr (VI) can be created during the procedure of oxidation dechroming, easily causing secondary pollution. Developing novel alternative dechroming methods will be urgent and some innovation methods have been proposed, such as, pyrolysis [109,110] and biochar dechroming [111].…”