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This paper presents a comprehensive analysis of the adsorbent capacity of five distinctly different biosorbents derived from untreated biomasses. The optimal adsorption capacity of seaweed (Laminaria digitata), horse chestnut husk, hazelnut husk, rapeseed residue, and whitewood to remove methylene blue (MB) dye was assessed by analysing the effects of particle size, pH, temperature, and initial dye concentrations. Furthermore, the adsorption kinetics, isotherms, and adsorption thermodynamics were investigated. The results showed that relatively high MB adsorption capacity was achieved by Laminaria digitata (~180 mg/g), in addition to a reasonable MB adsorption capacity of horse chestnut husk (~130 mg/g), hazelnut husk (~110 mg/g), and rapeseed residue (~80 mg/g). However, whitewood provides a relatively low adsorption capacity of below 20 mg/g. The best fit with experimental results regardless of biosorbent type was a pseudo-second-order kinetic model with the lowest mean absolute percentage error (ε, MAPE < 2.5%) and the highest correlation coefficients (R2 > 0.99). Although the pseudo-second-order kinetic model is often associated with chemisorption, the low enthalpy values (<29.30 kJ/mol) typically suggest that the adsorption process is more characteristic of physisorption, which involves weaker van der Waals forces rather than the stronger covalent bonds of chemisorption. This proposed a multi-step adsorption process involving both physisorption and chemisorption. The adsorption isotherm of Langmuir showed superior fitting results for Laminaria digitata and hazelnut husk. In contrast, rapeseed residue and horse chestnut husk fit better with the Freundlich adsorption isotherm. The Langmuir adsorption isotherms showed a maximum adsorption capacity of ~500 mg/g for Laminaria digitata, followed by horse chestnut husk (~137 mg/g), hazelnut husk (~120 mg/g), and rapeseed residue (~85 mg/g). The Gibbs free energy was negative for Laminaria digitata < horse chestnut husk < hazelnut husk < 0, which suggests that the removal of MB is thermodynamically favourable, as the adsorption process occurs spontaneously. The results of the study indicate that MB dye removal using untreated biomasses has the potential to be a low-cost valorisation option in the holistic whole life cycle valorisation pathway for Laminaria digitata, horse chestnut husk, and hazelnut husk. [ABSTRACT FROM AUTHOR]

Biomass-derived porous carbons have received enormous attention for CO 2 capture in post-combustion scenarios owing to their wide availability, excellent physicochemical stability, and cost-effective preparation. Here, a series of advanced bio-carbon materials were successfully prepared by using the underutilized industrial by-product Kraft lignin as precursor via a facile chemical activation process. Both the textural and surface properties of the bio-carbons were found to be highly tailorable by tuning the activation temperature, KOH/lignin ratio and pre-oxidation treatment. It was found that the Kraft lignin-derived carbons were exceedingly ultra-microporous with ultra-microporosity accounting for up to 92% of total micropores, while the carbons prepared with pre-oxidation treatment were uniquely characterised by distinctive hierarchical micro-mesoporous structures. Applying the Kraft lignin-derived carbons for CO 2 adsorption demonstrates that at a CO 2 partial pressure of 15 kPa, rarely obtainable CO 2 adsorption capacities of 3.29 mmol/g at 0 °C and 2.01 mmol/g at 25 °C were achieved for the carbon prepared at 600 °C. Advanced characterizations confirm that the unique desirable combination of textural properties and surface chemistry, which favours the intercalation of potassium in the form of surface extra-framework K+ ions, underpinned the extraordinary CO 2 adsorption performance and high CO 2 /N 2 selectivity (up to 38) of the prepared carbons especially at low CO 2 partial pressures. The results indicate that the unique three-dimensional aromatic structures of the lignin provide the matrix for the liable development of the well-defined ultra-microporosity at high levels. Our work provided a promising strategy for valorization of Kraft lignin as a precursor for producing advanced carbon materials. [Display omitted] • Advanced lignin-based carbons were prepared via a facile chemical activation process. • The bio-carbons have highly developed ultra-microporous structure (< 0.7 nm). • Superior CO 2 uptake of 2.01 mmol/g were achieved at low CO 2 partial pressure of 15 kPa and 25 °C. • Both surface chemistry and ultra-micropores contribute to the low-pressure CO 2 adsorption. [ABSTRACT FROM AUTHOR]

To impact carbon emissions, new materials for carbon capture must be inexpensive, robust, and able to adsorb CO2 specifically from a mixture of other gases. In particular, materials must be tolerant to the water vapor and to the acidic impurities that are present in gas streams produced by using fossil fuels to generate electricity. We show that a porous organic polymer has excellent CO2 capacity and high CO2 selectivity under conditions relevant to precombustion CO2 capture. Unlike polar adsorbents, such as zeolite 13x and the metal—organic framework, HKUST-1, the CO2 adsorption capacity for the hydrophobic polymer is hardly affected by the adsorption of water vapor. The polymer is even stable to boiling in concentrated acid for extended periods, a property that is matched by few microporous adsorbents. The polymer adsorbs CO2 in a different way from rigid materials by physical swelling, much as a sponge adsorbs water. This gives rise to a higher CO2 capacities and much better CO2 selectivity than for other water-tolerant, nonswellable frameworks, such as activated carbon and ZIF-8. The polymer has superior function as a selective gas adsorbent, even though its constituent monomers are very simple organic feedstocks, as would be required for materials preparation on the large industrial scales required for carbon capture. [ABSTRACT FROM AUTHOR]

This paper validates the hypothesis that the supposedly nonspecific adsorbates nitrogen and argon wet heavy metals differently and shows how this unexpected effect can be actively utilized to deliver information on pore interconnectivity. To explore surface chemistry influences on differential adsorbate wetting, new findings for a mixed silica-alumina material were compared with data for pure silica and alumina materials. The new structural characterization described can determine the distribution of the particular subset of meso- and micropores that connect directly to macropores that entrap mercury following porosimetry, as mapped by computerized X-ray tomography. Hence, it elucidates the spatial organization of the network and measures the improved accessibility to smaller pores provided by larger pores. It was shown that the silica-alumina pellets have a hierarchical pore-size arrangement, similar to the optimal blood vessel network architecture in animals. The network architecture derived from the new method has been independently validated using complementary gas sorption scanning curves, integrated mercury porosimetry, and NMR cryoporometry. It has also been shown that, rather than hindering interpretation of characterization data, emergent effects for networks associated with these techniques can be marshalled to enable detailed assessment of the pore structures of complex, disordered solids. [ABSTRACT FROM AUTHOR]

• Functionalized 3D carbon foams were prepared via single-step activation of PIR foam. • Carbon foams exhibit superior CO 2 sorption capacity and CO 2 /N 2 selectivity at 25 ℃. • Surface chemistry and micropores play key roles in determining the adsorption of CO 2. Porous carbon materials have been considered as the promising media for post combustion CO 2 capture. Development and design of cost-effective carbons with high adsorption capacity and selectivity of CO 2 over other gases at low CO 2 partial pressures has attracted increasing attention. In this study, a category of functionalized 3D microporous carbon foam was prepared by using inexpensive and commercially available polyisocyanurate foam (PIR) as the precursor via a facile one-step chemical activation process. The porous structure and surface chemistry of the carbon foams can be tailored by adjusting the activation temperature and KOH/PIR mass ratio. At 25 ℃ and a CO 2 partial pressure of 0.15 bar, the carbon foam of FC7001 with highest volume of fine micropores (<0.44 nm) and desirable surface chemistry exhibited exceptionally high CO 2 uptake of 2.3 mmol/g whereas FC6001, which had a pure single pore size centered at 0.37 nm, showed highest Henry's law CO 2 /N 2 selectivity of 200. Furthermore, high CO 2 uptake capacity of 19 mmol/g at CO 2 pressure of 20 bar and ambient temperature was obtained for the carbon foam prepared at a higher activation temperature and KOH/precursor ratio and with a high surface area of 2207 m2/g and micropore volume of 0.876 cm3/g. Advanced characterization confirmed that the unique ultra-microporous structure and surface chemistry originated from intercalated potassium in the form of surface extra-framework ions governed the selective CO 2 adsorption of the carbon foams at low CO 2 partial pressures whilst the high micropore volume determined the CO 2 adsorption at high CO 2 pressure. This work provides a potentially new pathway to recycle polyisocyanurate foams by producing efficient CO 2 adsorbents. [ABSTRACT FROM AUTHOR]