Treatment of Chromite Ore Processing Residue by pyrolysis with rice straw

Zhang, Dalei; He, Shengbing; Dai, Luwei; Hu, Xiaofang; Wu, Deyi; Peng, Kangjin; Bu, Guanhuan; Pang, Hao; Kong, Hainan

doi:10.1016/j.chemosphere.2009.08.023

Cited by 30 publications

(7 citation statements)

References 12 publications

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“…14 In previous research, a new technology for treatment of COPR was investigated. 15,16 In this process, COPR was initially mixed with rice straw and subsequently pyrolyzed at low temperatures. The Cr(VI) in COPR could be reduced into Cr(III) in less than 10 min of reaction time combined with low energy consumption of 43 kg of standard coal per ton of COPR.…”

Section: ■ Introductionmentioning

confidence: 99%

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Zhang

et al. 2016

Environ. Sci. Technol.

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ABSTRACT:The pyrolysis treatment with biomass is a promising technology for the remediation of chromite-oreprocessing residue (COPR). However, the mechanism of this process is still unclear. In this study, the behavior of pyrolysis reduction of Cr(VI) by cellulose, the main component of biomass, was elucidated. The results showed that the volatile fraction (VF) of cellulose, ie. gas and tar, was responsible for Cr(VI) reduction. All organic compounds, as well as CO and H 2 in VF, potentially reduced Cr(VI). X-ray absorption nearedge structure (XANES) spectroscopy and extended X-ray absorption fine-structure (EXAFS) spectroscopy confirmed the reduction of Cr(VI) to Cr(III) and the formation of amorphous Cr 2 O 3 . The remnant Cr(VI) content in COPR can be reduced below the detection limit (2 mg/kg) by the reduction of COPR particle and extension of reaction time between VF and COPR. This study provided a deep insight on the co-pyrolysis of cellulose with Cr(VI) in COPR and an ideal approach by which to characterize and optimize the pyrolysis treatment for COPR by other organics.

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Section: ■ Introductionmentioning

confidence: 99%

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Zhang

et al. 2016

Environ. Sci. Technol.

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“…11− 14 The current low-temperature pyrolysis reduction technology has achieved a pyrolysis reduction rate of 80−90%. 13,14 However, considering the high initial Cr(VI) concentration (∼10 000 mg/kg), there is still a large quantity of Cr(VI) (exceed 1000 mg/kg) that is not reduced. This will always result in a frequent reoccurrence of Cr(VI) in the remediated chromium slag, 15 also called the reyellowing phenomenon, causing a severe secondary threat to the ecosystem and to public health.…”

Section: Introductionmentioning

confidence: 99%

“…In order to remediate Cr(VI), various methods are applied, such as electro-dialysis, chelate, phytoremediation, and microbial remediation. − Most of these are expensive or have low removal efficiency . Therefore, the low-temperature pyrolysis reduction of Cr(VI) to nontoxic Cr(III) by biomass has been generally considered satisfactory for chromium slag treatment. − The current low-temperature pyrolysis reduction technology has achieved a pyrolysis reduction rate of 80–90%. , However, considering the high initial Cr(VI) concentration (∼10 000 mg/kg), there is still a large quantity of Cr(VI) (exceed 1000 mg/kg) that is not reduced. This will always result in a frequent reoccurrence of Cr(VI) in the remediated chromium slag, also called the reyellowing phenomenon, causing a severe secondary threat to the ecosystem and to public health. , Therefore, to avoid serious secondary pollution, realizing a highly reduction efficiency of Cr(VI) near 100% is urgently needed.…”

Section: Introductionmentioning

confidence: 99%

Biomass Cellulose Component and Fe Mineral Catalysis Help Cr(VI) to Realize Almost 100% Pyrolysis Reduction Efficiency

2021

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Low-temperature pyrolysis reduction (<500 °C) for Cr(VI) remediation in heavily polluted soil or slag has gained increasing attention. However, it is hard to realize almost 100% Cr(VI) pyrolysis reduction at a high concentration of Cr(VI) pollution (more than 104 mg/kg) due to insufficient reductive pyrolysis products. In the present study, almost 100% Cr(VI) reduction was achieved by cellulose-enriched biomass assisted by an Fe mineral catalysis. Quantitative analysis of tar, reducing gases, and char on the Cr(VI) reduction efficiency suggested that the produced tar is a crucial factor to promote Cr(VI) pyrolysis reduction. Our results indicated that both the cellulose component of biomass and the Fe minerals catalyst could produce susceptible-cracking tar to help Cr(VI) reduction indirectly. FT-ICR MS and online MS results further discerned that produced tar with aromatic and lignin/CRAM-like structures or high unsaturated and oxidized structures (DBE > 15, O x > O6) can be cracked via a decarbonylation reaction to generate reducing gases for promoting Cr(VI) reduction. Thus, our present study provides a method to completely reduce Cr(VI) in solid wastes, perfectly avoiding the reyellowing risk of residual Cr(VI).

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“…Most of these methods aim to reduce the hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) and to keep it in the mineral phase through ensuing treatments. 25 However, there have been some problems and limitations for these methods, including the large amount of the reducing agent used, high cost, 17 , 26 and the increased volume of residue after detoxification. 27 , 28 Besides, the components of the detoxified slag become more complicated because of the introduction of additional substances that make the subsequent resource utilization of the valuable elements difficult.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the COPR must be treated carefully. At present, the treatment of COPR focuses on environmentally friendly treatment by chemical reduction, hydrolysis, , electro-repair, stabilization/immobilization, , micro-organisms, biomass repair methods, ,− etc. Most of these methods aim to reduce the hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) and to keep it in the mineral phase through ensuing treatments .…”

Section: Introductionmentioning

confidence: 99%

Leaching of Valuable Elements from the Waste Chromite Ore Processing Residue: A Kinetic Analysis

Zhang

et al. 2020

ACS Omega

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The efficacious treatment and resource utilization of the chromite ore processing residue (COPR) is important for chromate salt production. In this study, the leaching of valuable elements from the waste COPR was investigated. X-ray diffraction (XRD) analysis showed that the COPR mainly contained periclase (MgCr 2 O 4 ), magnesiochromite ((Fe, Mg) (Cr, Fe) 2 O 4 ), Fe (Cr, Al) 2 O 4 , and MgFeAlO 4 . The optimum parameters for COPR leaching were as follows: mechanical ball-milling time of 120 min, sulfuric acid concentration (w/w % H 2 SO 4 ) of 60%, reaction temperature ( T ) of 403 K, liquid–solid ratio (L/S) of 8 mL/g, and reaction time ( t ) of 6 h. Under these conditions, the valuable components such as Fe, Al, and Cr were extracted with an ideal leaching efficiency of 94.8, 75.1, and 76%, respectively. The results of the leaching kinetics analysis indicated that the leaching of Fe and Cr from the COPR was controlled by a surface chemical reaction, and the leaching of Al was controlled by diffusion through a product layer. The apparent activation energy of the leaching of Fe, Cr, and Al was calculated to be 23.03, 44.15, and 17.54 kJ/mol, respectively. It is believed that this approach has potential applications for the chromate salt industry because of its advantage of ideal leaching efficiency.

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Treatment of Chromite Ore Processing Residue by pyrolysis with rice straw

Cited by 30 publications

References 12 publications

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Biomass Cellulose Component and Fe Mineral Catalysis Help Cr(VI) to Realize Almost 100% Pyrolysis Reduction Efficiency

Leaching of Valuable Elements from the Waste Chromite Ore Processing Residue: A Kinetic Analysis

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