Synchrotron X-ray microtomography and multifractal analysis for the characterization of pore structure and distribution in softwood pellet biochar

Srocke, Franziska; Han, Liwen; Dutilleul, Pierre; Xiao, Xianghui; Smith, Donald L.; Mašek, Ondřej

doi:10.1007/s42773-021-00104-3

Cited by 11 publications

(6 citation statements)

References 74 publications

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“…Overall, an increase in porosity, TSA, total pore volume, and VELP were observed with increasing pyrolysis temperature up to about 400-450 °C for all feedstocks. Many studies have reported an increase in the surface area, porosity and pore volume of biochar with increasing pyrolysis temperature 7,23,28,[34][35][36] .…”

Section: Visualization Of the Evolving Pore Structuresmentioning

confidence: 99%

4D structural changes and pore network model of biomass during pyrolysis

Edeh,

Masek,

Fusseis

2023

Sci Rep

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Biochar is an engineered carbon-rich substance used for soil improvement, environmental management, and other diverse applications. To date, the understanding of how biomass affects biochar microstructure has been limited due to the complexity of analysis involved in tracing the changes in the physical structure of biomass as it undergoes thermochemical conversion. In this study, we used synchrotron x-ray micro-tomography to visualize changes in the internal structure of biochar from diverse feedstock (miscanthus straw pellets, wheat straw pellets, oilseed rape straw pellets, and rice husk) during pyrolysis by collecting a sequence of 3D scans at 50 °C intervals during progressive heating from 50 °C to 800 °C. The results show a strong dependence of biochar porosity on feedstock as well as pyrolysis temperature, with observed porosity in the range of 7.41–60.56%. Our results show that the porosity, total surface area, pore volume, and equivalent diameter of the largest pore increases with increasing pyrolysis temperature up to about 550 °C. The most dramatic development of pore structure occurred in the temperature range of 350–450 °C. This understanding is pivotal for optimizing biochar’s properties for specific applications in soil improvement, environmental management, and beyond. By elucidating the nuanced variations in biochar’s physical characteristics across different production temperatures and feedstocks, this research advances the practical application of biochar, offering significant benefits in agricultural, environmental, and engineering contexts.

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Section: Visualization Of the Evolving Pore Structuresmentioning

confidence: 99%

4D structural changes and pore network model of biomass during pyrolysis

Edeh,

Masek,

Fusseis

2023

Sci Rep

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“…SEM imaging of SWP700 shows a highly porous framework consisting of macro- (Figures and S2), meso-, and micropores, which could be penetrated by water transporting dissolved Hg(II) species. Recent studies using the same biochar show that 95% of the total porosity in SWP700 corresponds to a pore width of <3 μm, with 1.4 and 7.8% consisting of micro- (<2 nm) and mesopores (2–50 nm), respectively . Hg(II) can be immobilized at sites on the external surface and within this porous framework.…”

Section: Resultsmentioning

confidence: 99%

Mercury Removal from Contaminated Water by Wood-Based Biochar Depends on Natural Organic Matter and Ionic Composition

Chaudhuri

Sigmund

Bone

et al. 2022

Environ. Sci. Technol.

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Biochars can remove potentially toxic elements, such as inorganic mercury [Hg(II)] from contaminated waters. However, their performance in complex water matrices is rarely investigated, and the combined roles of natural organic matter (NOM) and ionic composition in the removal of Hg(II) by biochar remain unclear. Here, we investigate the influence of NOM and major ions such as chloride (Cl – ), nitrate (NO 3 – ), calcium (Ca 2+ ), and sodium (Na + ) on Hg(II) removal by a wood-based biochar (SWP700). Multiple sorption sites containing sulfur (S) were located within the porous SWP700. In the absence of NOM, Hg(II) removal was driven by these sites. Ca 2+ bridging was important in enhancing removal of negatively charged Hg(II)-chloro complexes. In the presence of NOM, formation of soluble Hg-NOM complexes (as seen from speciation calculations), which have limited access to biochar pores, suppressed Hg(II) removal, but Cl – and Ca 2+ could still facilitate it. The ability of Ca 2+ to aggregate NOM, including Hg-NOM complexes, promoted Hg(II) removal from the dissolved fraction (<0.45 μm). Hg(II) removal in the presence of Cl – followed a stepwise mechanism. Weakly bound oxygen functional groups in NOM were outcompeted by Cl – , forming smaller-sized Hg(II)-chloro complexes, which could access additional intraparticle sorption sites. Therein, Cl – was outcompeted by S, which finally immobilized Hg(II) in SWP700 as confirmed by extended X-ray absorption fine structure spectroscopy. We conclude that in NOM containing oxic waters, with relatively high molar ratios of Cl – : NOM and Ca 2+ : NOM, Hg(II) removal can still be effective with SWP700.

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“…These modified BCs had larger specific surface areas, with more exposed active sites becoming denser due to the development of a three-dimensional network structure. 41 The layered structure disappeared and a denser porous structure was produced with an increase in the amount of La-BC and Fe-BC, but the disappearance of the layered structure in Fe-BC occurred slightly later than that of La-BC. The original Fe-BC had more phenolic hydroxyl groups forming an intermolecular hydrogen bond than La-BC, but the crosslinking (relative to amino groups) density was lower.…”

Section: Discussionmentioning

confidence: 95%

“…The density of the porous structure was higher for Fe-BC than La-BC, and that of straw-modified BC was the smallest. These modified BCs had larger specific surface areas, with more exposed active sites becoming denser due to the development of a three-dimensional network structure . The layered structure disappeared and a denser porous structure was produced with an increase in the amount of La-BC and Fe-BC, but the disappearance of the layered structure in Fe-BC occurred slightly later than that of La-BC.…”

Section: Discussionmentioning

confidence: 99%

Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water

Zheng

Yang

2023

ACS Omega

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In this study, a composite of pond mud and lanthanum-and nanozero valent iron-modified-biochar was investigated for its ability to adsorb methylene blue (MB) and sulfamethazine (SMZ). La-modified attapulgite and nano-zero valent iron (surface area enhanced by 43.7% via Brunauer−Emmett− Teller analysis) were successfully loaded onto the straw-sediment biochar (BC) surface. With the increase in pyrolysis temperature, the biocompatibility yield, the H, O, and N content, and the ratio of carbon elements decreased, while the pH value, surficial micropores, C element, and ash content increased. The biocarbon small molecules were gradually and tightly ordered, and the organic groups such as hydroxyl, carboxyl groups, and carbon oxygen double bonds were gradually lost or disappeared. The original Fe-BC had more phenolic hydroxyl groups forming an intermolecular hydrogen bond than others with a higher adsorption capacity possibly through the Schiff base reaction. The effect of various pH (2−9), temperature (15−35 °C), and initial concentration (1−25 mg L −1 ) on adsorption was investigated. pH and temperature were the main factors governing the adsorption process. The maximum adsorption capacity was observed at pH 4. The adsorption performances for MB followed the order Fe-BC > La-BC > BC, and the maximum removal rate was over 98.45% with pH = 7. The three types of BC dosages between 0.2 (6.67 g L −1 ) and 0.4 g showed a removal rate of 99% for MB. The adsorption capacity of Fe-BC, La-BC, and BC for MB was 2.201, 1.905, and 2.401 mg L −1 with pH = 4, while 4.79, 4.58, and 5.55 mg g −1 were observed with BC dosage at 0.025 g. For SMZ, the higher the temperature, the better the adsorption effect, and it reaches saturation at approximately 25 °C. To further evaluate the nature of adsorption, Langmuir/Freundlich/Temkin models were tested and the adsorption capacities were evaluated on the surface of the BC composite. The three modified materials were physisorbed to SMZ, while MB was chemisorbed. For MB, the adsorption performance of BC is the best < 0.2 g (6.67 g L −1 ) at pH 7.0 at 35 °C. The Elovich model was more suitable for MB, while the Freundlich and Temkin models could better fit the adsorption process of MB. The preparatory secondary dynamics equation and Langmuir equation were more compliant for SMZ, and the saturated adsorption capacities of straw-modified, La-BC, and Fe-BC reached 5.699, 6.088, and 5.678 mg L −1 , respectively.

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Synchrotron X-ray microtomography and multifractal analysis for the characterization of pore structure and distribution in softwood pellet biochar

Cited by 11 publications

References 74 publications

4D structural changes and pore network model of biomass during pyrolysis

4D structural changes and pore network model of biomass during pyrolysis

Mercury Removal from Contaminated Water by Wood-Based Biochar Depends on Natural Organic Matter and Ionic Composition

Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water

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