Brönsted Catalyzed Hydrolysis of Microcystin-LR by Siderite

Abstract

Six naturally occurring minerals were employed to catalyze the hydrolysis of microcystin-LR (MC-LR) in water. After preliminary screening experiments, siderite stood out among these minerals due to its higher activity and selectivity. In comparison with kaolinite, which is known to act as a Lewis acid catalyst, siderite was found to act primarily as a Brönsted acid catalyst in the hydrolysis of MC-LR. More interestingly, we found that the presence of humic acid significantly inhibited catalytic efficiency of kaolinite, while the efficiency of siderite remained high (∼98%). Reaction intermediates detected by LC-ESI/MS were used to indicate cleavage points in the macrocyclic ring of MC-LR, and XPS was used to characterize siderite interaction with MC-LR. Detailed analysis of the in situ ATR-FTIR absorption spectra of MC-LR indicated hydrogen bonding at the siderite-water-MC-LR interface. A metastable ring, involving hydrogen bonding, between surface bicarbonate of siderite and an amide of MC-LR was proposed to explain the higher activity and selectivity toward MC-LR. Furthermore, siderite was found to reduce the toxicity of MC-LR to mice by hydrolyzing MC-LR peptide bonds. The study demonstrates the potential of siderite, an earth-abundant and biocompatible mineral, for removing MC-LR from water.

Iron Minerals Mediated Interfacial Hydrolysis of Chloramphenicol Antibiotic under Limited Moisture Conditions

“…The mineral-surface-mediated hydrolysis of pollutants generally depends on the types of acidic sites on minerals, which include Brønsted acid, Lewis acid and H-bonding sites (Figure a–c). ,,, As shown in Figure , pure CAP exhibited three distinct IR absorption peaks at 1684, 1518, and 1344 cm –1 , respectively. According to our previous study, the peak at 1684 cm –1 was attributed to the stretching vibration of the carbonyl group ν­(CO) and the conjugated CN group (Table S1), and the other two IR signals corresponded to the characteristic bands of nitryl as asymmetric ν­(ONO) and symmetric ν­(C–NO 2 ) stretching vibrations, respectively. , When CAP interacted with the Brønsted acid sites (Figure a), the carbonyl oxygen of CAP would be protonated; subsequently, the ν­(CO) band should theoretically blue-shift (∼8 cm –1 ) due to the disintegration of NCO conjugation.…”

“…Previous studies indicated that iron minerals could mediate the transformation of organic pollutants and had been used as catalysts for soil remediation. − Specifically, the catalytic efficiency of iron minerals for the hydrolysis of contaminants is typically dependent on their surface properties. For example, it was reported that iron minerals, such as goethite (α-FeOOH) and hematite/maghemite (α-Fe 2 O 3 /γ-Fe 2 O 3 ), could catalyze the hydrolysis of phenyl picolinate and organophosphate via a surface chelation mechanism. − Nevertheless, Mäkie et al , proposed that the surface hydroxyl groups of goethite would be responsible for the hydrolysis of organophosphates. In addition, a recent study showed that siderite (FeCO 3 ) could selectively hydrolyze microcystin-LR via a Brønsted acid catalytic mechanism .…”

“…For example, it was reported that iron minerals, such as goethite (α-FeOOH) and hematite/maghemite (α-Fe 2 O 3 /γ-Fe 2 O 3 ), could catalyze the hydrolysis of phenyl picolinate and organophosphate via a surface chelation mechanism. − Nevertheless, Mäkie et al , proposed that the surface hydroxyl groups of goethite would be responsible for the hydrolysis of organophosphates. In addition, a recent study showed that siderite (FeCO 3 ) could selectively hydrolyze microcystin-LR via a Brønsted acid catalytic mechanism . Therefore, we suppose that iron mineral surfaces with exposed Fe and Fe–OH may provide sufficient Lewis acid, Brønsted acid, or hydrogen-bonding donor sites to catalyze the hydrolysis of antibiotics.…”

Detoxification of Cylindrospermopsin by Pyrite in Water

“…For the degradation system in the presence and absence of pyrite, the rate constants were 0.8842 and 0.0071 h −1 , and the half-lives were 0.78 and 98 h, respectively. Consequently, the presence of pyrite reduced the half-life of CYN in water by 99%, similar to the degradation systems of microcystin-LR (MC-LR) by kaolinite and siderite [12].…”

Enhancing Ethanol Oxidation Reaction Activity of P-Doped CuPdNi Nanocatalyst by Optimizing Surface-Atom Distribution

“…The direct ethanol fuel cell (DEFC) is a new type of environmentally friendly energy conversion device and has received a lot of attention in today’s energy crisis and environmental pollution problems. − The anode catalyst is an important part of the DEFC system. Pd-based catalysts have drawn more attention than Pt-based catalysts in anode catalyst research because of the lower cost and comparable activity to Pt toward ethanol electrooxidation under the alkaline system. , However, Pd-based catalysts have poor stability because they are easy to oxidize or dissolve, and this causes unnecessary loss of activity during the ethanol electrooxidation process.…”