Hydrothermal Carbon-Mediated Fenton-Like Reaction Mechanism in the Degradation of Alachlor: Direct Electron Transfer from Hydrothermal Carbon to Fe(III)

Abstract

As Fenton systems suffer from the undesirable Fe(III)/Fe(II) cycle, great efforts were made to realize the effective reduction of Fe(III) to Fe(II). The effects of hydrothermal carbon (HTC) on the Fe(III)/HO Fenton-like reaction and the subsequent degradation of alachlor in water was systematically investigated, and the results indicated that HTC could enhance alachlor degradation in Fe(III)/HO by promoting the Fe(III)/Fe(II) cycle via electron transfer from HTC to Fe(III) ions. The apparent alachlor degradation rate constant in the HTC-G/Fe(III)/HO system (7.02 × 10 min) was about 3 times higher than that in the Fe(III)/HO system (2.25 × 10 min). The electron spin resonance spectra analysis revealed that HTC consists of abundant carbon-centered persistent free radicals to act as the electron donor. Meanwhile, the hydroxyl groups on the surface of HTC also played an important role in the enhanced alachlor degradation because the decrease in the surface hydroxyl groups on HTC significantly decreased the degradation of alachlor. On the basis of these results, an Fe(III) complex with surface hydroxyl groups on HTC was proposed to favor the electron transfer from the hydroxyl groups to Fe(III), and then, the simultaneously produced Fe(II) could accelerate the catalytic decomposition of HO to facilitate alachlor degradation. These findings shed new light on the possible roles of carbon materials in a natural aquatic environment and provide a new pathway for environmental pollutant control and remediation of organic contaminants by HTC.

Biochar-Supported FeS/Fe3O4 Composite for Catalyzed Fenton-Type Degradation of Ciprofloxacin

“…The results indicate the biochar-supported composite is more stable than the unsupported one, which is beneficial for reusability of the biochar-supported catalyst. The reasons should be mainly attributed to the function of biochar as an electron donor that can help transform Fe 3+ into Fe 2+ [50]. There are many hydroquinone (Ar-OH) and quinone groups (Ar-C=O) on the biochar according to its infrared spectra shown in Figure S6.…”

“…There are many hydroquinone (Ar-OH) and quinone groups (Ar-C=O) on the biochar according to its infrared spectra shown in Figure S6. The conversion of biochar hydroquinone and quinone groups would donate electrons that promoted the Fe 2+ /Fe 3+ cycle [50,51], which is beneficial for increasing the yield of ·OH at the less consumption of H 2 O 2 (Figure 6b). In addition, pH change during the reaction in the two Fenton-type systems was also recorded, and results in Figure 7b indicate that pH in the FeS/Fe 3 O 4 @BC500 system is somewhat higher than that in the FeS/Fe 3 O 4 system.…”

A scientometric review of biochar research in the past 20 years (1998–2018)

“…The most commonly used method of modification was Fe (hydr) oxide/nanoscale zero-valent iron-supported biochar. Then the modified biochar activated H 2 O 2 to degrade organic pollutants under various Fenton-like oxidation conditions (Deng et al 2018a;Park et al 2018;Qin et al 2017b;Yan et al 2017;Zhang et al 2018).…”

Influence of precursor pH on the structure and photo-Fenton performance of Fe/hydrochar

“…Both Fe/HC-2 and Fe/HC-8 had rich oxygen-containing groups, and the loaded Fe might be coordinated to these groups, which could promote the cycle of Fe 3+ /Fe 2+ . 6,51,52 The bonds between Fe and oxygen-containing groups could be activated and cleaved with light irradiation. 53,54 Therefore, the photoreduction of Fe 3+ and Fe leaching occurred simultaneously.…”

“…According to literatures, HC with rich oxygen-containing groups could decrease the redox potential of Fe 3+ /Fe 2+ and might transfer electrons to Fe 3+ with light irradiation, thus accelerating the regeneration of Fe 2+ . 6,[49][50][51][52] Orange II is oxidized by cOH, which can be continuously produced through the Fe 2+ / Fe 3+ cycle at the Fe/HC/water interface.…”