Abstract
SummaryOxidative water purification of micropollutants (MPs) can proceed via toxic intermediates calling for procedures for connecting degrading chemical mixtures to evolving toxicity. Herein, we introduce a method for projecting evolving toxicity onto composite changing pollutant and intermediate concentrations illustrated through the TAML/H2O2 mineralization of the common drug and MP, propranolol. The approach consists of identifying the key intermediates along the decomposition pathway (UPLC/GCMS/NMR/UV-Vis), determining for each by simulation and experiment the rate constants for both catalytic and noncatalytic oxidations and converting the resulting predicted concentration versus time profiles to evolving composite toxicity exemplified using zebrafish lethality data. For propranolol, toxicity grows substantially from the outset, even after propranolol is undetectable, echoing that intermediate chemical and toxicity behaviors are key elements of the environmental safety of MP degradation processes. As TAML/H2O2 mimics mechanistically the main steps of peroxidase catalytic cycles, the findings may be relevant to propranolol degradation in environmental waters.
Highlights
Oxidation catalysis via monooxygenase and peroxidase enzymes provides Nature’s most commonly deployed and most potent tools for decomposing toxic organic compounds
The need for viable biomimicking catalytic solutions that, under ambient conditions, can safely treat vast quantities of wastewaters contaminated by ultradilute (%2 ppb) MPs demands that oxidation catalysts exhibit unprecedented technical and cost performances, and high health, environmental, and fairness performances (Somasundar, 2020; Warner et al, 2019)
As oxidative pollutant degradations can pass through potentially toxic intermediates that may be even more persistent and/or toxic than the starting MP before arriving at the safety of near-mineral to mineral endpoints, it is vital to understand the relative toxicities of all components in the degradation sequence and the composite evolving toxicity from the beginning to the end of a degradation process
Summary
Oxidation catalysis via monooxygenase and peroxidase enzymes provides Nature’s most commonly deployed and most potent tools for decomposing toxic organic compounds. Those that react too slowly with these enzymes turn up as persistent pollutants in water. Since Rachel Carson’s 1962 Silent Spring (Carson, 2002), a key water purification field for sustainability has awaited the design of synthetic catalysts that can activate natural oxidants such as H2O2 to effectively destroy persistent organic pollutants in scalable ways, cleaning water the way that Nature does, only better. As oxidative pollutant degradations can pass through potentially toxic intermediates that may be even more persistent and/or toxic than the starting MP before arriving at the safety of near-mineral to mineral endpoints, it is vital to understand the relative toxicities of all components in the degradation sequence and the composite evolving toxicity from the beginning to the end of a degradation process
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