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Lau CY, Yeung CS, Tse HY, Luk HL, Yu CY, Yuen CB, Phillips DL, Leu SY. Macrocyclic porphyrin photocatalysts without metal chelation: A novel pathway for complete degradation of tough halophenols with longwave visible LED light source. JOURNAL OF HAZARDOUS MATERIALS 2024; 478:135342. [PMID: 39126850 DOI: 10.1016/j.jhazmat.2024.135342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/17/2024] [Accepted: 07/25/2024] [Indexed: 08/12/2024]
Abstract
Halophenols are toxic and persistent pollutants in water environments which poses harm to various organisms. Due to their high stability and long residence time, ultraviolet radiation, heavy metals and oxidizing agents have been largely adopted on treating these compounds. However, these treatment methods could pose toxicity or hazardous risks to the marine environment and plant operators. In this study, a water-soluble porphyrin photocatalyst was synthesized and introduced for halophenol treatment using UV-free LED white light. The porphyrin catalyst is a macrocyclic ring consisting of pyrroles linked with methine bridges, the highly conjugated ring provided the superior functionality of visible light absorption. Surprisingly, over 99 % degradation of halophenols and over 90 % dehalogenation have been achieved without metal chelation, even higher than those of transition metal porphyrins with inclusion of Fe3+, Zn2+, Cu2+, Co2+, Ni2+, and Mn2+. Ring-opening reactions were confirmed with the formation of carboxylic acids; dicarboxylic acids like acrylic acid, and malonic acid; while fumaric acid was the main product. Total organic carbon results indicated no CO2 produced during the reaction. Triplet absorbance and scavenger studies also indicated that singlet oxygen and conduction band electrons are the main radical species for halophenol degradation. The 100-fold singlet emission quenching over triplet absorption quenching indicated that the excited electrons tend to be transferred via singlet state. This concept brings along new approaches detoxifying halophenol-related wastewater without UV, metals and other additives, which is more environmentally-friendly and sheds light to the conversion of toxic materials into useful chemical precursors.
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Affiliation(s)
- Chun-Yin Lau
- Department of Civil & Environmental Engineering, Hong Kong Polytechnic University, 11 Yuk Choi Rd., Hung Hom, Hong Kong
| | - Chi Shun Yeung
- Department of Civil & Environmental Engineering, Hong Kong Polytechnic University, 11 Yuk Choi Rd., Hung Hom, Hong Kong
| | - Ho-Yin Tse
- Department of Civil & Environmental Engineering, Hong Kong Polytechnic University, 11 Yuk Choi Rd., Hung Hom, Hong Kong; Center for Green Chemistry & Green Engineering at Yale, 370 Prospect St, New Haven, CT, USA; Yale School of the Environment, 195 Prospect St, New Haven, CT, USA
| | - Hoi Ling Luk
- Department of Chemistry, HKU-CAS Joint Laboratory on New Materials, University of Hong Kong, Hong Kong
| | - Chung Yin Yu
- Department of Civil & Environmental Engineering, Hong Kong Polytechnic University, 11 Yuk Choi Rd., Hung Hom, Hong Kong
| | - Chun Bong Yuen
- Department of Civil & Environmental Engineering, Hong Kong Polytechnic University, 11 Yuk Choi Rd., Hung Hom, Hong Kong
| | - David Lee Phillips
- Department of Chemistry, HKU-CAS Joint Laboratory on New Materials, University of Hong Kong, Hong Kong
| | - Shao-Yuan Leu
- Department of Civil & Environmental Engineering, Hong Kong Polytechnic University, 11 Yuk Choi Rd., Hung Hom, Hong Kong; Research Institute for Sustainable Urban Development (RISUD), The Hong Kong Polytechnic University, Hung Hom, Hong Kong.
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Gan J, Zhu T, Zhang Y, Li D, Li T, Zhao M, Zhao Z, Wang L. Degradation and dechlorination of trichloroacetic acid induced by an in situ 222 nm KrCl* excimer radiation. CHEMOSPHERE 2023; 331:138753. [PMID: 37100246 PMCID: PMC10122990 DOI: 10.1016/j.chemosphere.2023.138753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/08/2023] [Accepted: 04/20/2023] [Indexed: 05/07/2023]
Abstract
Since the coronavirus disease 2019 (COVID-19) pandemic epidemic, the excessive usage of chlorinated disinfectants raised the substantial risks of disinfection by-products (DBPs) exposure. While several technologies may remove the typical carcinogenic DBPs, trichloroacetic acid (TCAA), their application for continuous treatment is limited due to their complexity and expensive or hazardous inputs. In this study, degradation and dechlorination of TCAA induced by an in situ 222 nm KrCl* excimer radiation as well as role of oxygen in the reaction pathway were investigated. Quantum chemical calculation methods were used to help predict the reaction mechanism. Experimental results showed that UV irradiance increased with increasing input power and decreased when the input power exceeded 60 W. Decomposition and dechlorination were simultaneously achieved, where around 78% of TCAA (0.62 mM) can be eliminated and 78% dechlorination within 200 min. Dissolved oxygen showed little effect on the TCAA degradation but greatly boosted the dechlorination as it can additionally generate hydroxyl radical (•OH) in the reaction process. Computational results showed that under 222 nm irradiation, TCAA was excited from S0 to S1 state and then decayed by internal crossing process to T1 state, and a reaction without potential energy barrier followed, resulting in the breaking of C-Cl bond and finally returning to S0 state. Subsequent C-Cl bond cleavage occurred by a barrierless •OH insertion and HCl elimination (27.9 kcal/mol). Finally, the •OH attacked (14.6 kcal/mol) the intermediate byproducts, leading to complete dechlorination and decomposition. The KrCl* excimer radiation has obvious advantages in terms of energy efficiency compared to other competitive methods. These results provide insight into the mechanisms of TCAA dechlorination and decomposition under KrCl* excimer radiation, as well as important information for guiding research toward direct and indirect photolysis of halogenated DBPs.
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Affiliation(s)
- Jiaming Gan
- School of Environmental Science & Engineering, Xiamen University of Technology, Xiamen, 361024, PR China
| | - Ting Zhu
- School of Electrical Engineering and Automation, Xiamen University of Technology, Xiamen, 361024, PR China
| | - Yizhan Zhang
- School of Environmental Science & Engineering, Xiamen University of Technology, Xiamen, 361024, PR China
| | - Dailin Li
- School of Environmental Science & Engineering, Xiamen University of Technology, Xiamen, 361024, PR China
| | - Ting Li
- School of Environmental Science & Engineering, Xiamen University of Technology, Xiamen, 361024, PR China
| | - Min Zhao
- School of Environmental Science & Engineering, Xiamen University of Technology, Xiamen, 361024, PR China
| | - ZengXia Zhao
- International Joint Research Laboratory of Nano-Micro Architecture Chemistry, Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun, 130023, PR China
| | - Lei Wang
- School of Environmental Science & Engineering, Xiamen University of Technology, Xiamen, 361024, PR China.
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