Suggested improvements in the parameters used for describing the low relative pressure region of the water vapour isotherms of activated carbons

Lodewyckx, Peter; Raymundo-Piñero, E.; Václavíková, Miroslava; Berezovska, Inna; Thommes, Matthias; Béguin, François; Dobos, Gábor

doi:10.1016/j.carbon.2013.04.006

Cited by 19 publications

(22 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From XPS and ATR‐FTIR analyses, a wide variety of oxygenated functional groups exist on the external biochar surface, including phenol, ether, carbonyl, quinone, carboxyl, and ester groups. These functional groups were either preserved from the feedstock molecular structure (Keiluweit et al, 2010), formed during pyrolysis reactions at high temperatures (dehydration, depolymerization, and condensation) (Keiluweit et al, 2010; Lian & Xing, 2017), or are a result of air oxidation during preparation (rinsing and oven‐drying) and storing at the lab (Lodewyckx et al, 2013). Detailed information regarding peak assignments and the chemical state of the elements identified on the biochar surface are provided in the supporting information.…”

Section: Resultsmentioning

confidence: 99%

“…For ψ > −150 MPa, water clusters reach a critical size and dispersive forces cause clusters to merge and begin to fill the micropores (Figure 1a) (Do & Do, 2000; Lodewyckx et al, 2013; Velasco, Snoeck, et al, 2016). While it is known that micropores fill consecutively from smallest to largest and drain in the opposite direction (Alcañiz‐Monge et al, 2001; Do & Do, 2000; Velasco, Guillet‐Nicolas, et al, 2016), no model equation is postulated to predict the region of the WRC where micropore filling occurs.…”

Section: Methodsmentioning

confidence: 99%

“…Water retention in PCMs at low water potentials is caused by hydrogen bonding between water and oxygen at oxygenated surface functional groups. Water retention begins with sorption of water molecules onto active sites, and then, the sorbed water molecules act as secondary sites for further water adsorption and formation of water molecule clusters (Figure 1a) (Do & Do, 2000; Lodewyckx et al, 2013; Velasco, Snoeck, et al, 2016). For this situation, the gravimetric water content of biochar or other PCMs ( GWC b [kg/kg]) can be described using surficial oxygen concentration (Velasco, Snoeck, et al, 2016)

{GWC}_{b} ((), @ ψ \leq - 150 MPa) = \frac{((), 5 - 52 {[O]}^{3}) {[O]}^{2} \exp ((), ψ ϑ_{w} / italicRT)}{1 + ([], O) \exp ((), ψ ϑ_{w} / italicRT)}

where subscript b stands for biochar, [ O ] is surficial oxygen content (kg/kg carbon ), ϑ w is molar volume of water (m 3 /mol), R is universal gas constant (J/mol.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Models for Predicting Water Retention in Pyrogenic Carbon (Biochar) and Biochar‐Amended Soil at Low Water Contents

Nakhli

Imhoff

2020

Water Resources Research

View full text Add to dashboard Cite

The dry end of the soil water retention curve (WRC) plays an important role in various hydrologic, solute transport, plant, and microbial processes. Despite increasing application of biochar as a soil amendment, knowledge about water retention in biochars and biochar-amended soils under dry conditions is lacking. Mechanistic models are presented to predict the WRC for biochars and biochar-amended soils at matric potential (ψ) <~−1 MPa. For biochars, the amount of water retained is linked to biochar surficial oxygen content and pore volume and surface area distributions. The WRC for soils at dry conditions is predicted using specific surface area. The WRC model for biochar-amended soils is the sum of the contributions of models for biochar and soil. The model's utility was examined for three natural soils and a uniform sand, a wood-based biochar, and 10 different combinations of these soils and biochar. The accuracy of the model for biochars was further tested for six other pyrogenic carbonaceous materials (PCMs). The models agreed well with experimental data: for the biochar and PCMs, soils, and biochar-amended soils, the root mean square error normalized to the range of water content was almost always <10%. The line of best fit for predicted versus measured gravimetric water content at permanent wilting point had slope of 0.935 ± 0.013 and a coefficient of determination of 0.997. The applicability of these models for different biochars, soils, and their mixtures is discussed.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

{GWC}_{b} ((), @ ψ \leq - 150 MPa) = \frac{((), 5 - 52 {[O]}^{3}) {[O]}^{2} \exp ((), ψ ϑ_{w} / italicRT)}{1 + ([], O) \exp ((), ψ ϑ_{w} / italicRT)}

where subscript b stands for biochar, [ O ] is surficial oxygen content (kg/kg carbon ), ϑ w is molar volume of water (m 3 /mol), R is universal gas constant (J/mol.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Models for Predicting Water Retention in Pyrogenic Carbon (Biochar) and Biochar‐Amended Soil at Low Water Contents

Nakhli

Imhoff

2020

Water Resources Research

View full text Add to dashboard Cite

show abstract

“…Moreover, and after it has been recently demonstrated that water sorption gives information about the surface chemistry of some kind of materials (i.e. activated carbons) [60], a thorough modelling of these isotherms is expected to broaden their applicability towards the surface characterization of cements.…”

Section: Nitrogen Adsorption Isothermsmentioning

confidence: 99%

The effects of superabsorbent polymers on the microstructure of cementitious materials studied by means of sorption experiments

Snoeck

Velasco

Mignon

et al. 2015

Cement and Concrete Research

118

View full text Add to dashboard Cite

Keywords:Calcium-silicate-hydrate (C-S-H) Microstructure Texture Adsorption Carbonation Superabsorbent polymers (SAPs) are a promising additive to be used in the building industry but may induce microstructural changes. Water vapour sorption may be used to characterize the change in pore structure of cementitious materials, but the technique is difficult to interpret. In the present paper, static and dynamic vapour sorption (DVS) measurements were performed and compared to nitrogen adsorption experiments. The models of Dubinin-Radushkevich and Barrett-Joyner-Halenda were hereby applied to study pores in the micro-and mesopore range. The results show that cement pastes with SAPs and without additional water show a slight decrease in porosity in the micro-and mesopore range. Cement pastes with SAPs and with additional water show no significant change of porosity in the micropore range and a slight increase in the larger mesopore range. These new findings give insight into the effects of SAPs on the microstructure and strength of cementitious materials.

show abstract

“…It is well-established that water sorption is sensitive to surface chemistry (Bandosz et al, 1996 ; Thommes et al, 2011 ; Tóth and Lászlo, 2012 ; Lodewyckx et al, 2013 ; Nguyen et al, 2014 ). More specifically, it is assumed that water adsorption in carbon nanomaterials first proceeds through the clustering of water molecules around primary adsorption sites (functional surface groups).…”

Section: Introductionmentioning

confidence: 99%

Influence of Fluorine Doping of Activated Carbon Fibers on Their Water Vapor Adsorption Characteristics

et al. 2021

Self Cite

View full text Add to dashboard Cite

The characterization of fluorinated carbon fibers by water sorption has been broadly investigated in this work. In brief, a pitch-based activated carbon fiber (ACF) was submitted to a fluorination process under different conditions of partial pressure (F2:N2 ratio) and temperature. This led to samples with varied fluorine content and C-F type bonding. The effect of the fluorination treatment on the textural properties of the ACF was studied by means of nitrogen and carbon dioxide adsorption at −196 and 0°C, respectively, while the changes induced in the surface chemistry of the materials were analyzed by XPS. Also, the affinity and stability of the materials toward water was evaluated by single and cycling isotherms. The obtained results show that a mild fluorination not only can preserve most of the textural properties of the parent ACF, but enhance the water uptake at the first stages of the water sorption process, together with a shift in the upswing of the water isotherms toward lower relative humidities. This indicates that fluorination under certain conditions can actually enhance the surface hydrophilicity of carbon materials with specific properties. On the contrary, higher partial pressures led to highly fluorinated fibers with lower porosity and more hydrophobic character. Moreover, they presented a lower chemical stability as demonstrated by a change in the shape of the water isotherms after two consecutive measurements. The kinetics of water sorption in the ACFs provided further insights into the different sorption phenomena involved. Hence, water sorption can definitely help to tailor the water affinity, stability and performance of fluorinated porous carbon materials under humid conditions.

show abstract

Suggested improvements in the parameters used for describing the low relative pressure region of the water vapour isotherms of activated carbons

Cited by 19 publications

References 6 publications

Models for Predicting Water Retention in Pyrogenic Carbon (Biochar) and Biochar‐Amended Soil at Low Water Contents

Models for Predicting Water Retention in Pyrogenic Carbon (Biochar) and Biochar‐Amended Soil at Low Water Contents

The effects of superabsorbent polymers on the microstructure of cementitious materials studied by means of sorption experiments

Influence of Fluorine Doping of Activated Carbon Fibers on Their Water Vapor Adsorption Characteristics

Contact Info

Product

Resources

About