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Fe(III) photocatalytic reduction of Cr(VI) by low-molecular-weight organic acids with alpha-OH.
J Hazard Mater. 2009 Sep 15; 168(2-3):1569-74.JH

Abstract

The photochemical reduction of Cr(VI) by four low-molecular-weight organic acids (tartaric acid, citric acid, malic acid, and n-butyric acid) in the presence of either dissolved Fe(III) in dilute aqueous solution or adsorbed Fe(III) on clay mineral surfaces (kaolinite, montmorillonite and illite) was investigated using batch reactors at a pH range from 3.5 to 4.5 at 25 degrees C. The results indicate that Fe(III) photocatalytic reduction of Cr(VI) by organic acids with alpha-OH is extremely fast. During a reaction period when less than 80% initial Cr(VI) was consumed, the reaction can be described as pseudo-first-order with respect to Cr(VI) when organic acid in excess. By plotting ln[Cr(VI)] as a function of reaction time, rate constants of Cr(VI) reduction by organic acids are obtained. The rate constants involving the four acids are in the order: tartaric acid (with 2 carboxylic groups and 2 alpha-OH groups)>citric acid (with 3 carboxylic groups and 1 alpha-OH group) approximately malic acid (with 2 carboxylic groups and 1 alpha-OH group)>>n-butyric acid (with 1 carboxylic group and no alpha-OH group). This order suggests that the number of alpha-OH but not the number of carboxylic groups is an important determinant of kinetics. With light, the reduction of Cr(VI) by citric acid is accelerated by clay minerals. The enhancement of Cr(VI) reduction is attributed to the catalysis of Fe(III) adsorbed on clay mineral surfaces. However, such an acceleration is markedly suppressed by introducing NaF into the reaction system since NaF forms a complex with Fe(III). It is concluded that the complex formation between Fe(III) and organic acid is a key step for the photocatalytic reduction of Cr(VI) in the presence of Fe(III) and organic acids with alpha-OH.

Authors+Show Affiliations

College of Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19372002

Citation

Sun, Jun, et al. "Fe(III) Photocatalytic Reduction of Cr(VI) By Low-molecular-weight Organic Acids With Alpha-OH." Journal of Hazardous Materials, vol. 168, no. 2-3, 2009, pp. 1569-74.
Sun J, Mao JD, Gong H, et al. Fe(III) photocatalytic reduction of Cr(VI) by low-molecular-weight organic acids with alpha-OH. J Hazard Mater. 2009;168(2-3):1569-74.
Sun, J., Mao, J. D., Gong, H., & Lan, Y. (2009). Fe(III) photocatalytic reduction of Cr(VI) by low-molecular-weight organic acids with alpha-OH. Journal of Hazardous Materials, 168(2-3), 1569-74. https://doi.org/10.1016/j.jhazmat.2009.03.049
Sun J, et al. Fe(III) Photocatalytic Reduction of Cr(VI) By Low-molecular-weight Organic Acids With Alpha-OH. J Hazard Mater. 2009 Sep 15;168(2-3):1569-74. PubMed PMID: 19372002.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Fe(III) photocatalytic reduction of Cr(VI) by low-molecular-weight organic acids with alpha-OH. AU - Sun,Jun, AU - Mao,J-D, AU - Gong,Hui, AU - Lan,Yeqing, Y1 - 2009/03/21/ PY - 2008/09/12/received PY - 2009/03/09/revised PY - 2009/03/10/accepted PY - 2009/4/18/entrez PY - 2009/4/18/pubmed PY - 2009/9/12/medline SP - 1569 EP - 74 JF - Journal of hazardous materials JO - J Hazard Mater VL - 168 IS - 2-3 N2 - The photochemical reduction of Cr(VI) by four low-molecular-weight organic acids (tartaric acid, citric acid, malic acid, and n-butyric acid) in the presence of either dissolved Fe(III) in dilute aqueous solution or adsorbed Fe(III) on clay mineral surfaces (kaolinite, montmorillonite and illite) was investigated using batch reactors at a pH range from 3.5 to 4.5 at 25 degrees C. The results indicate that Fe(III) photocatalytic reduction of Cr(VI) by organic acids with alpha-OH is extremely fast. During a reaction period when less than 80% initial Cr(VI) was consumed, the reaction can be described as pseudo-first-order with respect to Cr(VI) when organic acid in excess. By plotting ln[Cr(VI)] as a function of reaction time, rate constants of Cr(VI) reduction by organic acids are obtained. The rate constants involving the four acids are in the order: tartaric acid (with 2 carboxylic groups and 2 alpha-OH groups)>citric acid (with 3 carboxylic groups and 1 alpha-OH group) approximately malic acid (with 2 carboxylic groups and 1 alpha-OH group)>>n-butyric acid (with 1 carboxylic group and no alpha-OH group). This order suggests that the number of alpha-OH but not the number of carboxylic groups is an important determinant of kinetics. With light, the reduction of Cr(VI) by citric acid is accelerated by clay minerals. The enhancement of Cr(VI) reduction is attributed to the catalysis of Fe(III) adsorbed on clay mineral surfaces. However, such an acceleration is markedly suppressed by introducing NaF into the reaction system since NaF forms a complex with Fe(III). It is concluded that the complex formation between Fe(III) and organic acid is a key step for the photocatalytic reduction of Cr(VI) in the presence of Fe(III) and organic acids with alpha-OH. SN - 1873-3336 UR - https://www.unboundmedicine.com/medline/citation/19372002/Fe_III__photocatalytic_reduction_of_Cr_VI__by_low_molecular_weight_organic_acids_with_alpha_OH_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0304-3894(09)00447-6 DB - PRIME DP - Unbound Medicine ER -