Anion exchange capacity of biochar

Lawrinenko, Michael; Laird, David A.

doi:10.1039/c5gc00828j

Cited by 178 publications

(91 citation statements)

References 69 publications

(125 reference statements)

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“…Spectra were fitted with Gaussian functions. As exemplified by the RF system, oxygen in all C(and EC)-RES-O(or D) was in equal amounts in the form of heteroaromatic pyrylium (O + at about 533 eV), [41] and charge-compensating phenoxide groups (O − at about 532 eV), [42,43] as published recently for the C aerogels. [35] Oxygen in C(and EC)-PBO was also in the form of pyrylium and CO -, whereas the latter probably overlaps with some CO also at around 532 eV, [44,45] hence the somewhat highest intensity peak.…”

Section: Methodsmentioning

confidence: 94%

Exceptionally High CO₂ Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Far

Rewatkar

Donthula

et al. 2018

Macro Chemistry & Physics

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Phenolic aerogels containing oxygen and other polymeric aerogels containing both oxygen and nitrogen (polybenzoxazine and a polyamide‐polyimide‐polyurea co‐polymer) are converted to carbon aerogels (800 °C/Ar), and are etched with CO2 (1000 °C). Etching opens closed pores and increases micropore volumes and size. Heteroatoms are retained in the etched samples. All carbon aerogels are evaluated as CO2 absorbers in terms of their capacity and selectivity toward CH4, H2, and N2. CO2 adsorption capacity is linked to microporosity. In most cases, monolayer coverage of micropore walls is enough to explain CO2 uptake quantitatively. The interaction of CO2 with micropore walls is evaluated via isosteric heats of adsorption, and is stronger with carbons containing only oxygen heteroatoms. The adsorption capacity of those carbons (5–6 mmol g−1) is on par with the best carbon and polymeric CO2 adsorbers known in the literature, with one exception however: etched carbon aerogels from low‐density resorcinol‐formaldehyde aerogels show a very high CO2 uptake (14.8 ± 3.9 mmol g−1 at 273 K, 1 bar) attributed to a pore‐filling process that proceeds beyond monolayer coverage, whereas surface phenoxides engage in a thermally neutral carbonate forming reaction (surface‐O– + CO2 → surface‐O–(CO)–O–) that continues until micropores are filled.

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Section: Methodsmentioning

confidence: 94%

Exceptionally High CO₂ Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Far

Rewatkar

Donthula

et al. 2018

Macro Chemistry & Physics

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“…Corn stover, red oak ( Quercus rubra L., RO), and CE (99% pure, from Sigma Aldrich) were used as biomass feedstocks to produce biochars in this study; because CS represents herbaceous feedstocks, RO represents woody feedstocks, and CE is a nearly pure material, which simplifies interpretations of chemical and spectroscopic evidence (Lawrinenko and Laird, 2015). Biochars were produced from CS, RO, and CE biomasses by slow pyrolysis using a programmable muffle furnace that heated biomass to highest treatment temperatures of 400, 500, 700, and 900°C under a N 2 purge (100 mL min −1 ).…”

Section: Methodsmentioning

confidence: 99%

“…None of these studies offered an explanation for the type of functional groups responsible for the positive surface charge on biochar surfaces. Lawrinenko and Laird (2015) were the first to investigate the nature of the positively charged functional groups on biochar surfaces. They reported that positive charge on biochar surfaces was due to pH-independent O heterocycles (oxonium groups) and, to a lesser extent, to pH-dependent N heterocycles (pyridinium groups) and condensed aromatic C, which may abstract protons from aqueous solutions at low pH.…”

Section: Impact Of Pyrolysis Temperature and Feedstock On Surface Chamentioning

confidence: 99%

“…The recent discovery that positive charge sites on biochar surfaces are partly due to oxonium groups (Lawrinenko and Laird, 2015) was a major advance in understanding biochar surface chemistry and opens the possibility of engineering biochars specifically for adsorption of anionic contaminants. However, the vulnerability of nonbridging oxoniums to hydrolysis under alkaline conditions (Lawrinenko et al, 2016) would make biochars dominated by nonbridging oxoniums unsuitable as adsorbents of anionic contaminates.…”

Section: Impact Of Pyrolysis Temperature and Feedstock On Surface Chamentioning

confidence: 99%

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Impact of Pyrolysis Temperature and Feedstock on Surface Charge and Functional Group Chemistry of Biochars

Lawrinenko²,

et al. 2018

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The capacity of biochars to adsorb ionic contaminants is strongly influenced by biochar surface chemistry. We studied the effects of biomass feedstock type, pyrolysis temperature, reaction media pH, and AlCl pre-pyrolysis feedstock treatments on biochar anion exchange capacity (AEC), cation exchange capacity (CEC), point of zero net charge (PZNC), and point of zero salt effect (PZSE). We used the relationship between PZNC and PZSE to probe biochar surfaces for the presence of unstable (hydrolyzable) surface charge functional groups. The results indicate that biochars produced at ≤500°C have high CECs and low AEC, PZSE, and PZNC values due to the dominance of negative surface charge arising from carboxylate and phenolate functional groups. Biochars produced at ≥700°C have low CEC and high AEC, PZSE, and PZNC values, consistent with a dominance of positive surface charge arising from nonhydrolyzable bridging oxonium (oxygen heterocycles) groups. However, biochars produced at moderate temperatures (500-700°C) have high PZSE and low PZNC values, indicating the presence of nonbridging oxonium groups, which are rapidly degraded under alkaline conditions by OH attack on the oxonium α-C. Biochars treated with AlCl have high AEC, PZSE, and PZNC values due to variably charged aluminol groups on biochar surfaces. The results provide support for the presence of both hydrolyzable and nonhydrolyzable oxonium groups on biochar surfaces. They also demonstrate that biochars produced at high pyrolysis temperatures (>700°C) or those receiving pre-pyrolysis treatments with AlCl are optimized for anionic contaminant adsorption, whereas biochars produced at low pyrolysis temperatures (400°C) are optimized for cationic contaminant adsorption.

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“…However, the existence of base functional groups including chromenes, ketones and pyrones on biochar can facilitate NO 3 --N adsorption to biochar (Montes- Morán et al, 2004;Amonette & Joseph, 2009). NO 3 --N adsorption is also possible via unconventional H-bonding between NO 3 --N ions and the biochar surface (Mukherjee et al, 2011;Lawrinenko, 2014;Kammann et al, 2015).…”

mentioning

confidence: 99%

Effects of biochar on soil available inorganic nitrogen: A review and meta-analysis

et al. 2017

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The interaction between biochar and soil changes nitrogen (N) dynamics in different ecosystems.Although multiple studies have reported influences of biochar on soil inorganic N (SIN) including ammonium (NH 4 + -N) and nitrate (NO 3 --N), the influences reported are contradictory. We undertook a meta-analysis to investigate how biochar properties and the interaction among biochar, soil and fertilisation affect SIN. This quantitative analysis used 56 studies with 1080 experimental cases from manuscripts published between 2010 and 2015. Overall, we found that biochar reduced SIN regardless of experimental conditions (approximately -11±2% of NH 4 + -N and -10±1.6% of NO 3 --N); however, 95% of cases were observed within one year after biochar application. SIN was best explained by residence time of biochar in soil, pyrolysis temperature, application rate, fertiliser type, and soil pH. The effects of biochar were complex due to the interaction of biochar with environmental factors. Most biochar trials used wood as a feedstock, but woody biochar did not decrease SIN as much as other plant-derived biochars. When biochar was used with NH 4 -based fertilisers, SIN decreased compared to biochar with no fertiliser. In contrast, adding organic fertiliser with biochar increased SIN compared to biochar alone. SIN was clearly reduced after one month of biochar application, suggesting that biochar should be applied at least one month prior to planting so plants are not affected by decreased N. Our results revealed that the interactions between biochar and environmental factors, pyrolysis temperature of biochar and biochar surface properties are the main driving factors affecting SIN. There were limited long term studies of greater than 1 year, thus the long term effects of biochar on SIN still remain unclear.

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Anion exchange capacity of biochar

Abstract: Biochar has gained recent interest as a soil amendment and agent for carbon sequestration.

Cited by 178 publications

References 69 publications

Exceptionally High CO₂ Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Exceptionally High CO₂ Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Impact of Pyrolysis Temperature and Feedstock on Surface Charge and Functional Group Chemistry of Biochars

Effects of biochar on soil available inorganic nitrogen: A review and meta-analysis

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Anion exchange capacity of biochar

Abstract: Biochar has gained recent interest as a soil amendment and agent for carbon sequestration.

Cited by 178 publications

References 69 publications

Exceptionally High CO2 Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Exceptionally High CO2 Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Impact of Pyrolysis Temperature and Feedstock on Surface Charge and Functional Group Chemistry of Biochars

Effects of biochar on soil available inorganic nitrogen: A review and meta-analysis

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Resources

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Exceptionally High CO₂ Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels

Exceptionally High CO₂ Adsorption at 273 K by Microporous Carbons from Phenolic Aerogels: The Role of Heteroatoms in Comparison with Carbons from Polybenzoxazine and Other Organic Aerogels