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Chemosphere. 2018 Nov;210:224-231. doi: 10.1016/j.chemosphere.2018.07.006. Epub 2018 Jul 4.

Photodegradation of amitriptyline in Fe(III)-citrate-oxalate binary system: Synergistic effect and mechanism.

Author information

1
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
2
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China. Electronic address: ychen@hust.edu.cn.
3
University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747-2300, USA.

Abstract

Fe(III) and carboxylic acids are ubiquitous in surface water and atmospheric water droplets. Numerous documents have reported the photochemistry of Fe(III)-carboxylate complexes, typically including Fe(III)-oxalate and Fe(III)-citrate. Our previous study preliminarily showed that oxalate enhances the photoreactivity of Fe(III)-citrate system. Here, we further investigate the synergistic effect of Fe(III)-citrate-oxalate binary system at different conditions with pharmaceutical amitriptyline (AMT) as the model pollutant. In the Fe(III)-oxalate system, the photodegradation of AMT decreased with increasing pH from 3.0 to 8.0. In the Fe(III)-citrate system, the optimal pH for AMT degradation is around 5.0 in the same pH range. For the Fe(III)-citrate-oxalate system, the photodegradation of AMT decreased with increasing pH, indicating the combined effect of both oxalate and citrate on the photoreactivity. The addition of oxalate to the Fe(III)-citrate system markedly accelerated the photodegradation of AMT. The Fe(III)-carboxylate binary system exhibited excellent photoreactivity and up to 90% AMT was removed after 30 min at pH 6.0 with Fe(III)/citrate/oxalate ratio of 10:150:500 (μM). Synergistic effect was observed in Fe(III)-citrate-oxalate binary system in the pH range of 5.0-8.0. The presence of oxalate promoted the depletion of citrate in the Fe(III)-citrate system. The higher concentration ratios of oxalate to citrate facilitated the synergistic effect in the Fe(III)-citrate-oxalate system. By LC-MS analyses, a possible pathway of AMT degradation was proposed based on hydroxyl radicals (OH) mechanism. This finding could be helpful for the better understanding of synergistic mechanism of Fe(III)-citrate-oxalate binary complexes, which will be of great potential application in environmental photocatalysis at near neutral pH.

KEYWORDS:

Amitriptyline; Fe(III)-citrate-oxalate; Mechanism; Photodegradation; Synergistic effect

[Indexed for MEDLINE]

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