搜索结果：Biochar

Manganese(II) mobilised by mining activity poses a persistent water-quality challenge, yet the mechanisms by which low-cost sorbents, such as biochar, sequester Mn(II) remain poorly resolved. This study identifies the specific chemical drivers of Mn(II) sequestration by combining fixed-bed column and batch experiments with atomistic molecular dynamics simulations. Oilseed rape straw biochars, produced at 350\textdegree C, 550\textdegree C, and 700\textdegree C, removed 20-50% of dissolved Mn from acidic influent (pH 4, 5 ppm). High-temperature biochar achieved the greatest removal ($\sim$50%) and rapidly increased effluent pH to 9, triggering alkaline precipitation. Conversely, lower-temperature biochars removed 20-30% of Mn while maintaining a near-neutral pH (7-7.5). Enhanced \ce{K+} release in these systems indicates significant cation exchange and non-precipitative pathways. Molecular simulations confirmed that while neutral surfaces show weak Mn(II) association, deprotonated sites drive strong adsorption through inner-sphere complexation ($\sim$50% removal) and outer-sphere association ($\sim$10%). These results establish a mechanistic framework to distinguish between precipit

Biochars are an exciting class of environmental materials with a wide range of applications, including carbon storage and sequestration, soil enhancement, and pollution remediation. However, the limited knowledge of their molecular structures and compositions and the lack of comprehensive understanding of the relationship between these structures and biochars' diverse functionality, is hindering advancements in their development. In this work, we further advance the approach, first introduced by Wood et al. (2023), to constructing biochar molecular models; and now include control of microporosity (pores < 2 nm size) within the developed models. We construct biochar models representative of woody biochars which are experimentally produced at 600 -- 650 oC highest heating temperatures. Our models reproduce experimental H/C and O/C atomic ratios, percentage aromatic carbon, true density, cumulative porosity, and pore size distribution. The development of microporous biochar molecular models allows us to identify the importance of chemical structures involved in the assembly of biochar materials, and describe the relationship between these structures and obtained micropores. To faci

We report a molecular dynamics investigation of 2,4-dichlorophenoxyacetic acid (2,4-D) adsorption at the aqueous-biochar interface using experimentally constrained woody biochar models representative of softwood-derived biochars produced at 400, 600 and 800 $°$C. The models reproduce experimental descriptors (H/C, O/C, aromaticity, true density, and surface functionality) of their experimental counterparts, and simulations enable calculation of adsorption isotherms that align with available experimental measurements. Our results reveal that 2,4-D$^{-}$ uptake is governed by a synergy of three interaction classes: (i) $π$-$π$ and $π$-Cl contacts with graphitic domains with either parallel or perpendicular alignments, (ii) polar interactions including H-bonding to surface -OH and other oxygen-containing groups, and (iii) Na$^{+}$-mediated cation bridging that links 2,4-D$^{-}$ anion to surface oxygens, that would have an increasing relevance for biochars near or above the pH at point of zero charge. Notably, we found that low-temperature produced biochars, which retain higher densities of surface O functionalities, exhibit higher adsorption per unit surface area due to cooperative po

This study presents a closed-loop biorefinery strategy that thermochemically upcycles fermentation residues (FRs) from photo-fermentative biohydrogen production (PFHP) into functional biochar catalysts, thereby enhancing the efficiency of the initial PFHP process. Four FRs derived from hydrothermal and ethylene glycol-pretreated corn stover were pyrolyzed at 700°C. Multi-model kinetic analyses revealed diffusion-controlled mechanisms with activation energies ranging from 157 to 278 kJ/mol, while thermodynamic profiling highlighted the influence of feedstock composition on reaction spontaneity and entropy. Pyrolysis effectively restored porosity compromised during fermentation, yielding biochar with tailored properties: microporous BC3 (185 m2/g) from oxygen-rich precursors and mesoporous BC4 (76.58 m2/g) from graphitized residues. When reintroduced into PFHP, BC3 maximized cumulative hydrogen yield (570 mL) via pH buffering, and BC4 achieved the highest production rate (14.91 mL/h) through electron shuttle mechanisms. The integrated process concurrently generated syngas, bio-oil, and catalytic biochar, enabling waste valorization, renewable energy output, and process enhancement wi

The global Biochar Industry has witnessed a surge in biochar production, with a total of 350k mt/year production in 2023. With the pressing climate goals set and the potential of Biochar Carbon Removal (BCR) as a climate-relevant technology, scaling up the number of new plants to over 1000 facilities per year by 2030 becomes imperative. However, such a massive scale-up presents not only technical challenges but also control and regulation issues, ensuring maximal output of plants while conforming to regulatory requirements. In this paper, we present a novel method of optimizing the process of a biochar plant based on machine learning methods. We show how a standard Random Forest Regressor can be used to model the states of the pyrolysis machine, the physics of which remains highly complex. This model then serves as a surrogate of the machine -- reproducing several key outcomes of the machine -- in a numerical optimization. This, in turn, could enable us to reduce NOx emissions -- a key regulatory goal in that industry -- while achieving maximal output still. In a preliminary test our approach shows remarkable results, proves to be applicable on two different machines from different

Biochars are black carbonaceous solids produced through biomass pyrolysis under conditions of little or no oxygen. Whilst their properties are well studied, and their applications numerous, the underlying molecular structures within biochars still need to be defined. This raises a substantial barrier to the molecular modelling of biochars and has limited computational study of these materials, despite the advantages of such techniques. In this work, we critically assess the analytical techniques used to characterise biochars and use this information to gain molecular-level insights into biochars' molecular compositions and nanostructures. We focus on properties present at the nanoscale and which provide atomic-resolution insights into the molecular structures within these materials. Our goal is to create a holistic understanding of biochars' chemical, physical and molecular properties and to lay the foundation for future work focused on developing realistic molecular models of these materials.

Biochars have been attracting renewed attention as economical and environmentally friendly carbon sequestration materials with a diverse range of applications. However, experimental developments may be limited by the lack of molecular-level knowledge of the key interactions driving these applications. Molecular modelling techniques, such as molecular dynamics simulations, offer a systematic and reproducible alternative and yield atomistic insights into physicochemical processes, allowing the identification of adsorption mechanisms and, through this, informing and guiding experimental development. In this work, on the basis of the critical assessment of the analytical techniques for characterisation of biochars and collation of a large volume of experimental data, we develop molecular models of three woody biochar materials, representative of those produced under low-, medium-, and high-temperature treatments. We characterise these models, validating them against experimental data, and share them with the research community. Furthermore, we detail our iterative approach to the design of these biochar models, discuss what we have learned about the relationship between biochar composi

Pyrolysis techniques have served to be a groundbreaking technique for effectively utilising natural and man-made biomass products like plastics, wood, crop residue, fruit peels etc. Recent advancements have shown a greater yield of essential products like biochar, bio-oil and other non-condensable gases by blending different biomasses in a certain ratio. This synergy effect of combining two pyrolytic raw materials i.e co-pyrolysis of algae and wood biomass has been systematically studied and grouped into 3 phases in this research paper-kinetic analysis of co-pyrolysis, correlation among proximate and ultimate analysis with bio-char yield and lastly grouping of different weight ratios based on biochar yield up to a certain percentage. Different ML and DL algorithms have been utilized for regression and classification techniques to give a comprehensive overview of the effect of the synergy of two different biomass materials on biochar yield. For the first phase, the best prediction of biochar yield was obtained by using a decision tree regressor with a perfect MSE score of 0.00, followed by a gradient-boosting regressor. The second phase was analyzed using both ML and DL techniques.

Pore space characteristics of biochars may vary depending on the used raw material and processing technology. Pore structure has significant effects on the water retention properties of biochar amended soils. In this work, several biochars were characterized with three-dimensional imaging and image analysis. X-ray computed microtomography was used to image biochars at resolution of 1.14 $μ$m and the obtained images were analysed for porosity, pore-size distribution, specific surface area and structural anisotropy. In addition, random walk simulations were used to relate structural anisotropy to diffusive transport. Image analysis showed that considerable part of the biochar volume consist of pores in size range relevant to hydrological processes and storage of plant available water. Porosity and pore-size distribution were found to depend on the biochar type and the structural anisotopy analysis showed that used raw material considerably affects the pore characteristics at micrometre scale. Therefore attention should be paid to raw material selection and quality in applications requiring optimized pore structure.

Biochar pore space consists of porosity of multiple length scales. In direct water holding applications like water storage for plant water uptake, the main interest is in micrometre-range porosity since these pores are able to store water that is easily available for plants. Gas adsorption measurements which are commonly used to characterize the physical pore structure of biochars are not able to quantify this pore-size range. While pyrogenetic porosity (i.e. pores formed during pyrolysis process) tends to increase with elevated process temperature, it is uncertain whether this change affects the pore space capable to store plant available water. In this study, we characterized biochar porosity with x-ray tomography which provides quantitative information on the micrometer-range porosity. We imaged willow dried at 60 $^\circ$C and biochar samples pyrolysed in three different temperatures (peak temperatures 308, 384, 489 $^\circ$C, heating rate 2 $^\circ$C min$^{-1}$). Samples were carefully prepared and traced through the experiments, which allowed investigation of porosity development in micrometre size range. Pore space was quantified with image analysis of x-ray tomography image