Superior CO₂ adsorption from waste coffee ground derived carbons

Abstract

Utilising the hugely abundant waste from spent coffee grounds (CGs), KOH activated highly microporous carbons with surface areas of 2785 m 2 g À1 and micropore volumes of 0.793 cm 3 g À1 were synthesised that are capable of uptake capacities near 3 mmol g À1 at 50 C and 1 bar. Importantly such uptake capacities are achieved though the material's superior microporous character and without doping within the carbon matrix, thereby ensuring facile regeneration with a binding enthalpy of only 26 kJ mol À1 and therefore being capable of energy unintensive cycleable adsorption processes. Furthermore, excellent tunability of pore-size is demonstrated from narrow micropores through to narrow mesopores, enabling optimised adsorption over a range of pressures.

Superior Multifunctional Activity of Nanoporous Carbons with Widely Tunable Porosity: Enhanced Storage Capacities for Carbon‐Dioxide, Hydrogen, Water, and Electric Charge

“…For instance, the sample that exhibits predominant porosity of around 0.7 nm along with a much smaller proportion of pores of size below 1.5 nm and SSA BET of 1551 m 2 g −1 has shown CO 2 uptake of 7.4 mmol g −1 . Microporous carbons derived from coffee‐waste show CO 2 capacity of 7.5 and 7.2 mmol g −1 for SSA BET of 1620 and 2070 m 2 g −1 , respectively, with more than 90% of the porosity in the <1.5 nm region . UMCs also exhibit a clear porosity‐dependent uptake trend, where a linear correlation can be established between uptakes and SSA BET or micropore volume (Figure c,g).…”

“…Specifically, at a low CO 2 partial pressure of 0.15 bar, as a standard concentration in the postcombustion flue‐gas, the samples with ultranarrow pores show high CO 2 capture capacity, reaching to 2.75 mmol g −1 (≈12.1 wt%). The maximum capacity of 7.9 mmol g −1 (≈34.6 wt%) at 1 bar is also one of the highest values reported so far in the wide range of porous solids, including N‐doped activated carbons (ACs), MOFs (of open‐metal centers, micropores and flexible frameworks), microporous polymers, and solid‐amines . Uptake values deduced at 273 K and 1 bar in such different categories of materials family with respect to their SSA BET are comparatively summarized in Figure g.…”

Importance of Micropore–Mesopore Interfaces in Carbon Dioxide Capture by Carbon‐Based Materials

“…Theadsorption isotherms showed that the pores in starch-derived Starbons were disordered slit-shaped (H3type isotherm according to IUPAC classification), whilst those in alginic acid-based Starbons were interconnected ink-bottle shaped (H2-type isotherm). [11] It is apparent from Figure 1t hat some of the Starbon samples could outperform the CO 2 adsorption capacity of AC by up to 50 %(and by up to 65 %at10bar CO 2 pressure). Themass difference between the end of the pressurization and vacuum steps was used to calculate the number of mmols of CO 2 adsorbed per gram of sample.…”

The Potential of Activated Carbon Made of Agro-Industrial Residues in NOx Immissions Abatement

“…Referring to the recent work published on chemically activated carbon, it is shown that this yield is more important that KOH activation of biomass. Travis et al [23] have synthesized a series of KOH activated carbons from spent coffee grounds. Sample yields ranged from 11 to 16 wt % with yields lower for higher KOH.…”