Self-heating of dried industrial tannery wastewater sludge induced by pyrophoric iron sulfides formation
| Autor: | Roberta Bertani, M. Della Zassa, Paolo Canu, M. Zerlottin, A. Biasin, D. Refosco, Fabio Simionato |
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| Rok vydání: | 2015 |
| Předmět: |
Exothermic reaction
Environmental Engineering 020209 energy Health Toxicology and Mutagenesis 02 engineering and technology 010501 environmental sciences engineering.material Combustion 01 natural sciences Pyrophoricity Pyrophoric iron sulfides Self-heating Tannery sludge Tannery wastewater 0202 electrical engineering electronic engineering information engineering Environmental Chemistry Waste Management and Disposal Pyrrhotite 0105 earth and related environmental sciences Waste management Chemistry Pollution Anoxic waters Wastewater Environmental chemistry engineering Sewage treatment Pyrite |
| Zdroj: | Journal of hazardous materials. 305 |
| ISSN: | 1873-3336 |
| Popis: | Similarly to many powders of solids, dried sludge originated from tannery wastewater may result in a self-heating process, under given circumstances. In most cases, it causes a moderate heating (reaching 70-90°C), but larger, off-design residence times in the drier, in a suboxic atmosphere, extremely reactive solids can be produced. Tannery waste contains several chemicals that mostly end up in the wastewater treatment sludge. Unexpected and uncontrolled self heating could lead to a combustion and even to environmental problems. Elaborating on previous studies, with the addition of several analytical determinations, before and after the self-heating, we attempted to formulate a mechanism for the onset of heating. We demonstrated that the system Fe/S/O has been involved in the process. We proved that the formation of small quantities of pyrophoric iron sulfides is the key. They are converted to sulfated by reaction with water and oxygen with exothermic processes. The pyrite/pyrrhotite production depends on the sludge drying process. The oxidation of sulfides to oxides and sulfates through exothermic steps, reasonably catalyzed by metals in the sludge, occurs preferentially in a moist environment. The mechanism has been proved by reproducing in the laboratory prolonged heating under anoxic/suboxic atmosphere. |
| Databáze: | OpenAIRE |
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