Optimum utilization and resource recovery of tannery sludge: a review

Sunmathi, N.; Padmapriya, R.; Sudarsan, J. S.; Nithiyanantham, S.

doi:10.1007/s13762-022-04483-3

Cited by 1 publication

(1 citation statement)

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“…Various strategies are devised for tannery sludge management and disposal, such as its use in agriculture and landfilling 13 , 14 . Even if Cr(VI) salts are generally not used in tanning, and Cr in the fresh sludge is expected to persist in its trivalent state due to the high content of organic substances 15 , it is necessary to ensure that Cr(III) remains resistant to the conversion to the hexavalent form during disposal in oxidizing environments 16 , since Cr(VI) compounds are highly toxic and group one human carcinogens 17 .…”

Section: Introductionmentioning

confidence: 99%

Hexavalent chromium release over time from a pyrolyzed Cr-bearing tannery sludge

Ghezzi,

Mugnaioli,

Perchiazzi

et al. 2023

Sci Rep

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Pyrolysis in an inert atmosphere is a widely applied route to convert tannery wastes into reusable materials. In the present study, the Cr(III) conversion into the toxic hexavalent form in the pyrolyzed tannery waste referred to as KEU was investigated. Ageing experiments and leaching tests demonstrated that the Cr(III)–Cr(VI) inter-conversion occurs in the presence of air at ambient temperature, enhanced by wet environmental conditions. Microstructural analysis revealed that the Cr-primary mineral assemblage formed during pyrolysis (Cr-bearing srebrodolskite and Cr-magnetite spinel) destabilized upon spray water cooling in the last stage of the process. In the evolution from the higher to the lower temperature mineralogy, Cr is incorporated into newly formed CrOOH flakes which likely react in air forming extractable Cr(VI) species. This property transforms KEU from an inert waste to a hazardous material when exposed to ordinary ambient conditions.

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