TY - JOUR
T1 - Inhibitory effects and mechanisms of low-molecular-mass organic acids (LMMOAs) toward Cr(III) oxidation
AU - Ng, Kim Hoong
AU - Liu, Yu Ting
AU - Chang, Chung Tse
AU - Chiang, Po Neng
AU - Teah, Heng Yi
AU - Chang, Po Hsiang
AU - Tzou, Yu Min
N1 - Funding Information:
This work is financially supported by the Ministry of Science and Technology, Republic of China (ROC) , under project numbers 109-2326-B-005 -002 -MY3, and 107-2313-B-005-033-MY3. This work is also supported by the Innovation and Development Center of Sustainable Agriculture from the Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education in Taiwan.
Publisher Copyright:
© 2021 Elsevier Ltd
PY - 2021/9/1
Y1 - 2021/9/1
N2 - Photo-reduction of Cr(VI) into Cr(III) has been extensively studied for the alleviation of Cr(VI) hazards. However, knowledge in regard to the Cr(III) oxidation back into Cr(VI), which serves an equally important role in controlling Cr pollution, is limited. To this end, inhibitory effects and related mechanisms of low-molecular-mass organic acids (LMMOAs), including citric acid, oxalic acid and acetic acid, toward Cr(III) oxidation in the presence of Fe(III) under UV-irradiation were determined in this study. Results showed that the most prominent Cr(III) oxidation (~4 μM out of 300 μM Cr(III)) occurred at pH 3.0 in the presence of 400 μM Fe(III) and 12 h of UV-irradiation, yet such Cr(III) oxidation could be entirely or partially suppressed upon the addition of LMMOAs. Both citric and oxalic acids triggered a nearly complete inhibition of Cr(III) oxidation, even with the lowest dosage of 50 μM, ascribed to promoted generation of Fe(II) that scavenged OH• radicals. Regarding acetic acid, the addition of 50 μM only yielded 75% inhibitory efficiency, and further decreased to 50% as its amount increased to 400 μM. In contrast with citric/oxalic acids, acetic acid tended not to complex with Fe(III). While such free acetic acid reacted with OH• radicals generated from photolysis of Fe(OH)2+, additional OH• radicals were produced. Furthermore, the Fe(II) generation in the acetic acid system was about 28–35% of that in the citric/oxalic acid systems. In the case of supplementary OH• radicals and insufficient Fe(II), less OH• radicals could be consumed, and thereby the amendment of acetic acid showed a relatively weak inhibitory effect toward Cr(III) oxidation. This study evidenced that all three LMMOAs are effective toward the inhibition of Cr(III) oxidation in the presence of Fe(III). This feasible, practical, and environmental friendly approach is promising to prevent the secondary pollution caused by Cr(III) oxidation.
AB - Photo-reduction of Cr(VI) into Cr(III) has been extensively studied for the alleviation of Cr(VI) hazards. However, knowledge in regard to the Cr(III) oxidation back into Cr(VI), which serves an equally important role in controlling Cr pollution, is limited. To this end, inhibitory effects and related mechanisms of low-molecular-mass organic acids (LMMOAs), including citric acid, oxalic acid and acetic acid, toward Cr(III) oxidation in the presence of Fe(III) under UV-irradiation were determined in this study. Results showed that the most prominent Cr(III) oxidation (~4 μM out of 300 μM Cr(III)) occurred at pH 3.0 in the presence of 400 μM Fe(III) and 12 h of UV-irradiation, yet such Cr(III) oxidation could be entirely or partially suppressed upon the addition of LMMOAs. Both citric and oxalic acids triggered a nearly complete inhibition of Cr(III) oxidation, even with the lowest dosage of 50 μM, ascribed to promoted generation of Fe(II) that scavenged OH• radicals. Regarding acetic acid, the addition of 50 μM only yielded 75% inhibitory efficiency, and further decreased to 50% as its amount increased to 400 μM. In contrast with citric/oxalic acids, acetic acid tended not to complex with Fe(III). While such free acetic acid reacted with OH• radicals generated from photolysis of Fe(OH)2+, additional OH• radicals were produced. Furthermore, the Fe(II) generation in the acetic acid system was about 28–35% of that in the citric/oxalic acid systems. In the case of supplementary OH• radicals and insufficient Fe(II), less OH• radicals could be consumed, and thereby the amendment of acetic acid showed a relatively weak inhibitory effect toward Cr(III) oxidation. This study evidenced that all three LMMOAs are effective toward the inhibition of Cr(III) oxidation in the presence of Fe(III). This feasible, practical, and environmental friendly approach is promising to prevent the secondary pollution caused by Cr(III) oxidation.
KW - Chromium
KW - Ferric ion
KW - Inhibitory mechanism
KW - Low-molecular-mass organic acids
KW - Oxidation
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U2 - 10.1016/j.jclepro.2021.127726
DO - 10.1016/j.jclepro.2021.127726
M3 - Article
AN - SCOPUS:85107748571
SN - 0959-6526
VL - 313
JO - Journal of Cleaner Production
JF - Journal of Cleaner Production
M1 - 127726
ER -
