Changes of chromium speciation and organic matter during low-temperature pyrolysis of tannery sludge

Zhou, Jianjun; Ma, Hongwen; Gao, Mao; Sun, Wenyue; Zhu, Chao; Chen, Xiangping

doi:10.1007/s11356-017-0271-0

Cited by 19 publications

(5 citation statements)

References 41 publications

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“…In the temperature range of 400–1200 °C, the Cr mass content in the PDS char sample increases with the increase in the pyrolysis temperature. With the increase in the pyrolysis temperature, the fixing ratio of Cr showed a trend increasing gradually, and Zhou also obtained the same result. Because Cr is one kind of semivolatile heavy metal, the PDS sludge contains more chloride, and Cr may volatilize in the form of chromium chloride during pyrolysis.…”

Section: Resultssupporting

confidence: 53%

Transformation of Heavy Metals during Pyrolysis of Predried Dyeing Sludge

2019

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Heavy metals in sludge may cause serious pollution and restrict the industrial application of sludge heat treatment. In this paper, predried dyeing sludge (PDS) char samples were prepared on a fixed bed in a pure nitrogen atmosphere. X-ray diffractometry, microwave digestion, and inductively coupled plasma-atomic emission spectrometry were used to measure the content, speciation occurrence, and the transformation of heavy metals during heat treatment of PDS samples. The results show that heavy metal elements such as Cr, Cu, Hg, Ni, and Pb in PDS both in raw PDS and derived char samples are mainly dominated by hydrochloric acid soluble speciation and insoluble speciation, while the ammonium acetate soluble speciation is very little and the water soluble speciation is negligible. Part of the hydrochloric acid soluble Cr is volatilized when pyrolyzed at 400−600 °C. Cr is mainly fixed in the PDS char as the insoluble speciation and hydrochloric acid soluble speciation above 600 °C. One part of the hydrochloric acid soluble Cu is volatilized and the other part transforms to the insoluble speciation at 400−500 °C. Cu is mainly fixed in the PDS char in the insoluble state above 600 °C. A small amount of Hg transforms from the hydrochloric acid soluble speciation to the gaseous speciation. Ni is observed to transform from the hydrochloric acid soluble speciation to the insoluble speciation below 700 °C, while it transforms from the insoluble speciation to the hydrochloric acid soluble speciation above 700 °C. The higher the temperature is, the more the ammonium acetate soluble Pb and the hydrochloric acid soluble Pb released to by volatilization as gaseous Pb. The fixing ratio of Cr, Cu, and Ni is proportional to the pyrolysis temperature, and the fixing ratio of Hg and Pb is inversely proportional to the pyrolysis temperature. PDS has a high fixing ratio of heavy metals at 700−800 °C, which indicates the best temperature window for heavy metal fixing. The present results may be helpful for the prevention and control of heavy metals in PDS.

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Section: Resultssupporting

confidence: 53%

Transformation of Heavy Metals during Pyrolysis of Predried Dyeing Sludge

2019

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“…The results of XRD analyses therefore indicated that the Cr(III) was the main form, and no Cr(VI)containing crystalline phases were found by XRD, which may be limited by the low Cr(VI) content compared to high amount of Cr(III). Similar results were found by Zhou et al (2018) who pyrolyzed tannery sludge during low temperature, and XRD results showed that no Cr(VI)-containing components were found by XRD although their tannery sludge had a high concentration of total Cr. In addition, no obvious mineral transform was found during the process of pyrolysis treatment at 300°C .…”

Section: Also Reportedsupporting

confidence: 85%

“…It was also reported by Zhou et al (2018) that the total concentration of Cr was high but lower in the leachate. The decrease of leachable Cr after co-pyrolysis treatments could be ascribed to the degradation of organic matter and the formation of undissolved compounds with calcium, copper and alkali.…”

Section: According To the Identification Standards For Hazardous Wastsupporting

confidence: 51%

Treatment of chromium contaminated soil by co-pyrolysis with rice straw

Chen¹

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The direct discharge of tannery waste and effluent could result in severe chromium (Cr) contamination in soils. This study focused on the remediation of Cr-contaminated soil via copyrolysis with rice straw. The influence of co-pyrolysis temperature, rice straw / soil mixing ratio and reaction time on Cr immobilization were investigated. Compared to untreated soil, the leachable Cr and total Cr(VI) in co-pyrolyzed soil were decreased by up to 95 % and 86 %, respectively. With increasing temperature and rice straw addition, the leachable Cr and total Cr(VI) were reduced. Reaction time did not show a significant effect on Cr immobilization. The time-varying desorption test indicated that the equilibrium amount of released Cr in various extractants was inhibited by co-pyrolysis. The Simple Bioaccessibility Extraction Test also showed that the bioaccessible Cr in the gastric phase was decreased after co-pyrolysis. The results suggested that co-pyrolysis was beneficial on Cr immobilization.

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“…It was deduced that Cr(III) may be oxidized to Cr(VI) during the calcination process forming soluble compounds that were responsible for the increased Cr leachability (Zhu et al, 2018). In contrast, the suppression of Cr leaching after pyrolysis may be due to the complexation with copper and calcium that could immobilize Cr (Zhou et al, 2018). Further, according to the 2003/33/EC, leaching of Clslightly exceeded (or around the borderline) the hazardous waste criteria in R-ESP (16873 ± 214 mg/kg) and C-ESP (17021 ± 203 mg/kg) samples after the pyrolysis experiment.…”

Section: Metal Leachingmentioning

confidence: 99%