Impact of pyrolysis process on the chromium behavior of COPR

Zhang, Dalei; He, Shengbing; Dai, Luwei; Xie, Yaning; Wu, Deyi; Bu, Guanhua; Peng, Kangjin; Kong, Hainan

doi:10.1016/j.jhazmat.2009.08.032

Cited by 18 publications

(9 citation statements)

References 14 publications

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“…Even at low concentrations Cr(VI) compounds are known to have carcinogenic effects (Shi et al, 2009). Some disposal sites are capable of generating leachates containing up to 100 mg L -1 Cr(VI) (Geelhoed et al, 2002;Wang et al, 2010;Zhang et al, 2009;Sahinkaya et al, 2012;O'Conell et al, 2008), compared to the maximum contamination level of 0.1 mg L -1 for chromium set by the US Environmental Protection Agency (EPA) (Badruddoza et al, 2013). The ion exchange removal of Cr(VI) has received considerable interest (Table 1) and the fastest rate and highest sorption capacity of Cr(VI) have been achieved using amino-functionalised titanate nanotubes (Wang et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

A preliminary batch study of sorption kinetics of Cr(VI) ions from aqueous solutions by a magnetic ion exchange (MIEX®) resin and determination of film/pore diffusivity

et al. 2016

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A magnetic ion exchange resin was tested for the removal of Cr(VI) ions from aqueous solutions in a batch reactor at different resin dosages (0.5-1.5 g L -1 ), pH values (2-10), temperatures (25 o C-55 o C) and initial concentrations of Cr(VI) (0.11 -2.12 mmol L -1 or 5.7-110 mg L -1 ). The experimental data were evaluated using kinetic models based on the rate controlling steps relevant to pseudo-first order or pseudo-second order reactions or diffusion through fluid film or pores of the MIEX resin beads. Fast uptake of Cr(VI) ions by MIEX resin facilitates the attainment of equilibrium within 60 minutes. The sorption process is strongly dependent on the initial pH of the solution with maximum occurring at pH 4-6. The sorption of Cr(VI) at equilibrium increases with the increase in initial concentration according to the Langmuir isotherm, with a maximum sorption capacity of 93 mg g -1 on MIEX resin.Relatively low activation energy of 43 kJ mol -1 at a high initial concentration of 1 mmol L -1 Cr(VI) suggests a mixed chemical-diffusion controlled process, supported by the agreement of the sorption results with the homogeneous particle diffusion model with a film diffusivity of D f = 1 × 10 -9 m 2 s -1 and a pore diffusivity of D p = 8 × 10 -13 m 2 s -1 .

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Section: Introductionmentioning

confidence: 99%

A preliminary batch study of sorption kinetics of Cr(VI) ions from aqueous solutions by a magnetic ion exchange (MIEX®) resin and determination of film/pore diffusivity

et al. 2016

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Section: Introductionmentioning

confidence: 99%

“…In previous research, a new technology for treatment of COPR was investigated. , 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 . The pilot-scale experiment with 20 t of COPR per day (shown in Note S1 of the Supporting Information) indicated that the treatment cost is less than 30 USD per ton of COPR.…”

Section: Introductionmentioning

confidence: 99%

“…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. 16 The pilot-scale experiment with 20 t of COPR per day (shown in Note S1 of the Supporting Information) indicated that the treatment cost is less than 30 USD per ton of COPR. In addition, the dry process reduced the volume of the treated material, and the pyrolysis product of the biomass (i.e., the char) is environmentally friendly.…”

Section: ■ Introductionmentioning

confidence: 99%

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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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“…Millions of tons of COPR have been deposited in urban areas around the world including UK, USA, India, Pakistan and China [2][3][4]. Cr(VI) continues to leach out from sites abandoned over 40 years ago at concentrations of up to 100 mg L −1 [5,6].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of chromium bioaccessibility in chromite ore processing residue using in vitro gastrointestinal method

Luo

et al. 2012

Journal of Hazardous Materials

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a b s t r a c tIncidental ingestion of Chromite ore processing residue (COPR) particles poses a potential health risk. The purpose of this study was to determine the Cr bioaccessibility from COPR using the in vitro gastrointestinal (IVG) procedure. The bioaccessible Cr(VI) was 53.8% and 42.9%, respectively, in the gastric and intestinal phases from a total of 19 490 mg kg −1 Cr(VI) in COPR. Food intake including milk, dough, and ascorbic acid resulted in a significant decrease in Cr(VI) bioaccessibility. Some organic acids such as lactic, malic, and citric acid moderately reduced Cr(VI), while acetic acid exhibited no capacity for Cr(VI) reduction. The integrated area under the concentration-time curve (AUC) of the IVG extraction was used to calculate bioaccessibility. Compared with the bioaccessibility conventionally estimated using concentrations at the end of the extraction (CEP), the AUC technique should be implemented to confirm the accuracy of the IVG method when reduction of Cr(VI) occurs during the extraction. The absence of Cr(VI) phases in extracted residues as evidenced by XANES and XRPD analysis confirmed the Cr(VI) release and Cr(VI) reduction by food and ascorbic acid. With readily bioaccessible Cr(VI) and rapid human uptake, reduction of Cr(VI) might not be as effective a detoxification pathway as initially thought.

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Impact of pyrolysis process on the chromium behavior of COPR

Cited by 18 publications

References 14 publications

A preliminary batch study of sorption kinetics of Cr(VI) ions from aqueous solutions by a magnetic ion exchange (MIEX®) resin and determination of film/pore diffusivity

A preliminary batch study of sorption kinetics of Cr(VI) ions from aqueous solutions by a magnetic ion exchange (MIEX®) resin and determination of film/pore diffusivity

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

Evaluation of chromium bioaccessibility in chromite ore processing residue using in vitro gastrointestinal method

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