Abstract
Complex wastewater with massive components is now a serious environmental issue facing humanity. Selective removal of low-concentration contaminants in mixed constituents holds great promise for increasing water supplies. Bioenzymes like horseradish peroxidase exhibit oxidizing power and selectivity. Here, we manufactured its mimic through immobilizing non-heme oxamate anionic cobalt(III) complex ([CoIII(opba)]−, opba = o-phenylenebis(oxamate)) onto pyridine (Py) modified multiwalled carbon nanotubes ([CoIII(opba)]−-Py-MWCNTs, MWCNTs = multiwalled carbon nanotubes), where MWCNTs captured substrates and Py functioned as the fifth ligand. We chose typical azo dye (C.I. Acid Red 1) and antibiotic (ciprofloxacin) as model substrates. Without •OH, this catalyst could detoxify target micropollutants efficiently at pH from 8 to 11. It also remained efficient in repetitive tests, and the final products were non-poisonous OH-containing acids. Combined with radical scavenger tests and electron paramagnetic resonance result, we speculated that high-valent cobalt-oxo active species and oxygen atom transfer reaction dominated in the reaction pathway. According to density functional theory calculations, the electron spin density distribution order showed that electron-withdrawing ligand was beneficial for inward pulling the excess electron and lowering the corresponding energy levels, achieving an electrophilic-attack enhancement of the catalyst. With target removal property and recyclability, this catalyst is prospective in water detoxication.
Highlights
Thousands of industrial and agriculture chemical compounds are being discharged into freshwater system without effective treatment [1,2]
As the content of active entity on multiwalled carbon nanotubes (MWCNTs) is directly related to catalytic activity, TGA and atomic absorption spectrometry (AAS) were employed to detect the loading amount of [CoIII]−
The results showed that the adsorption of Acid Red 1 (AR1) by MWCNTs was enhanced in the existence ofphenomenon, NaCl, urea or PEG
Summary
Thousands of industrial and agriculture chemical compounds are being discharged into freshwater system without effective treatment [1,2]. Most toxic pollutants featured with stubborn conjugated structure appear at trace concentrations such as dyes, antibiotics and pesticides, but many of them cause pathogenic concerns due to their chemical durability and bioaccumulation [3,4,5]. The inadequate access to clean water and sanitation is afflicting billions of people throughout the world, and millions of them die annually from pollutant transmission through impure water. Detoxification of wastewaters is considered as one of the most inexpensive and effective campaigns to protect public health and save lives [6]. One of the challenges should be the achievement of targeted hazardous component detoxification to guarantee treatment efficiency [7]
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