Pyrolysis-temperature depended electron donating and mediating mechanisms of biochar for Cr(VI) reduction

Xu, Zibo; Xu, Xiaoyun; Zhang, Yue; Yu, Yulu; Cao, Xinde

doi:10.1016/j.jhazmat.2019.121794

Cited by 128 publications

(55 citation statements)

References 53 publications

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“…In contrast, the conjugated π-electron system of the iron−char composite produced under high-temperature pyrolysis contributed to mediating the electron-transfer pathway. 22 Considering these merits, we speculate that the iron−char composite/PS system have the potential to coordinate different nonradical ROS pathways including Fe(IV) and mediated electron transfer. However, the relations of treatment temperature, property of composites, and regime of oxidation are still unclear.…”

Section: ■ Introductionmentioning

confidence: 96%

Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Liang

Duan

et al. 2021

Environ. Sci. Technol.

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234

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Despite the vital roles of reactive radical species in the coupled iron–carbon composite/persulfate (PS) system for eliminating pollutants, nonradical contributions are typically overlooked. Herein, we developed two efficient magnetic iron–char composites via low-temperature (BCFe-400) and high-temperature (BCFe-700) pyrolysis. The two composites activated PS through nonradical pathways for sulfamethoxazole (SMX) degradation. In the BCFe-400/PS system, high-valent iron Fe(IV) was the dominant active species for the oxidation, evidenced by methyl phenyl sulfoxide-based probe tests, Mössbauer spectroscopy, and in situ Raman analyses with kinetic evaluation. In the BCFe-700/PS system, surface-mediated electron transfer dominated the oxidation, and the nonradical regime was probed by the electrochemical test and in situ Raman analysis. Furthermore, the BCFe-400/PS system maintained high efficiency in continuous degradation of SMX due to the feasible Fe2+generation toward Fe(IV) formation. In the BCFe-700/PS system, the stability of the system was limited due to the hindered electron transfer between the surface reactive complex (i.e., BCFe-700–PS*) and SMX, and thermal treatment would help recover the reactivity. Both BCFe-400/PS and BCFe-700/PS systems exhibited high performances for SMX removal in the presence of chloride and humic acid and in real water matrixes (e.g., seawater, piggery wastewater, and landfill leachate), exhibiting the great merits of the nonradical system. Overall, the study would provide new insights into PS activation by iron-loaded catalysts to efficiently degrade pollutants via nonradical pathways.

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Section: ■ Introductionmentioning

confidence: 96%

Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Liang

Duan

et al. 2021

Environ. Sci. Technol.

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234

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“…A small peak at 2,930 cm À1 and 2,860 cm À1 corresponding to C-H was observed in LB and FLB (Zhang et al 2020). Peak at 1,740 cm À1 corresponded to ester C ¼ O structure, while peak at 1,620 cm À1 corelated with phenolic C ¼ O functional group (Xu et al 2020). Strong stretching vibration of C-O at 1,040 cm À1 could be caused by hemicellulose and lignin (Gan et al 2016), which accounted for a higher intensity in LB and FLB than that in four biochars.…”

Section: Adsorbent Characterizationmentioning

confidence: 95%

Adsorption of heavy metals by Lycium barbarum branch-based adsorbents: raw, fungal modification, and biochar

Guan

Zhou

et al. 2022

Water Science and Technology

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The present study reports on the adsorptive removal of heavy metals (Cr3+, Cd2+, and Cu2+) from water by a series of Lycium barbarum branch-based adsorbents: Lycium barbarum branch (denoted as LB), fungal fermented LB (FLB), LB biochar (LBB), FLB biochar (FLBB), alkaline modified LBB (ALBB), and alkaline modified FLBB (AFLBB). The six adsorbents were characterized in terms of FTIR, SEM, surface area and pore size as well as Zeta potential. Adsorptive potential of these adsorbents was tested under varying conditions – pH, contact time, initial concentration, and temperature. Adsorption results were well fitted with Langmuir, Freundlich, and Temkin models. The maximum adsorption capacity (qm) was calculated to be 6.29 mg/g for Cr3+ by FLB, 11.53 mg/g for Cd2+ by LB, and 7.27 mg/g for Cu2+ by LB. Pseudo-second-order kinetic equation better described the adsorption process. Based on the thermodynamics parameters, the adsorption of heavy metals was endothermic but not spontaneous for biochars. The experimental results offer a new way for recycling and reutilizing LB in wastewater treatment.

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“…Moreover, phenol would transform to quinone with the increase of temperature, leading to the transition of reductive biochar to oxidative biochar (Klüpfel et al 2014a;Xin et al 2021). In addition, other oxygen-containing functionalities (e.g., carboxyl, hydroxyl, and carbonyl) may be responsible for the electron transfer capacity of biochar (Xu et al 2020c;Zhang et al 2019b;Zhong et al 2019). In addition to the reversible electron transfer through surface functionality (geo-battery), the conductivity of biochar facilitates a fast electron transfer routine, also denoted as the geo-conductor mechanism (Fig.…”

Section: Biocharmentioning

confidence: 99%

“…The structural defects on the graphitic carbon structure, which widely occur on the pyrogenic carbon and graphene, also provide considerable reducing activity for Cr(VI) reduction (Xu et al 2020c). The reduction of Cr(VI) by organic carbon is facilitated under the following conditions: (i) an acidic environment (Xu et al 2019b); (ii) accelerated electron transfer with redoxactive metal ions (i.e., iron (Fe) and manganese (Mn)) (Xu et al 2020b(Xu et al , 2021c; (iii) condensed graphitic structure on pyrogenic carbon (e.g., biochar) for fast electron transfer (Sun et al 2017;Xu et al 2020c); (iv) cations for overcoming the charge repulsion (Xu et al 2021c); and (v) accumulation of Cr(VI) and organic carbon on the solid surface.…”

Section: Reductionmentioning

confidence: 99%

“…The impact of different organic carbon on fertility, soil remediation, and carbon sequestration is systematically studied (Hoffland et al 2020;Lehmann and Kleber 2015;Maestrini et al 2015;Ondrasek et al 2019; Smreczak and Ukalska-Jaruga 2021; Verbeeck et al 2020;Woolet and Whitman 2020), and their potential role in the abiotic redox-induced transformation of pollutants in soil has been highlighted recently (Aftabtalab et al 2022;LaCroix et al 2021;Xu et al 2020cXu et al , 2022b. The considerable redox capacity of organic carbon could directly affect the redox reaction of potentially toxic elements (PTEs), which are the trace elements with the potential toxicity to humans.…”

Section: Introductionmentioning

confidence: 99%

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Redox-induced transformation of potentially toxic elements with organic carbon in soil

Tsang

2022

carbon res

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Soil organic carbon (SOC) is a crucial component that significantly affects the soil fertility, soil remediation, and carbon sequestration. Here, we review the redox-induced transformation of potentially toxic elements (PTEs) through the abiotic impact of SOC. The complex composition of SOC includes humus, pyrogenic carbon (e.g., biochar), dissolved organic matter, and anthropogenic carbon (e.g., compost), with varying concentrations and properties. The primary redox moieties on organic carbon are surface functionalities (e.g., phenol, quinone, and N/S-containing functional groups), environmentally persistent free radicals, and graphitic structures, and their contents are highly variable. Owing to these rich redox moieties, organic carbon can directly affect the reduction and oxidation of PTEs in the soil, such as Cr(VI) reduction and As(III) oxidation. In addition, the interactions between organic carbon and soil redox moieties (i.e., O2, Fe, and Mn minerals) cause the transformation of PTEs. The formation of reactive oxygen species, Fe(II), and Mn(III)/Mn(II) is the main contributor to the redox-induced transformation of PTEs, including Cr(VI) reduction and As(III)/Cr(III)/Tl(I) oxidation. We articulated both the positive and negative effects of organic carbon on the redox-induced transformation of PTEs, which could guide soil remediation efforts. Further scientific studies are necessary to better understand the potential transformations of PTEs by SOC, considering the complicated soil moieties, variable organic carbon composition, and both biotic and abiotic transformations of PTEs in the environment. Graphical Abstract

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Pyrolysis-temperature depended electron donating and mediating mechanisms of biochar for Cr(VI) reduction

Cited by 128 publications

References 53 publications

Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Persulfate Oxidation of Sulfamethoxazole by Magnetic Iron-Char Composites via Nonradical Pathways: Fe(IV) Versus Surface-Mediated Electron Transfer

Adsorption of heavy metals by Lycium barbarum branch-based adsorbents: raw, fungal modification, and biochar

Redox-induced transformation of potentially toxic elements with organic carbon in soil

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