Sustainable coffee‐based CO₂ adsorbents: toward a greener production via hydrothermal carbonization

Abstract

Activated carbons for adsorption of CO2 under flue gas conditions were prepared by means of hydrothermal carbonization (HTC) and subsequent CO2 activation of spent coffee grounds. The HTC of the samples consisted of their heating at moderate temperature with a high water content in autoclave. A preliminary screening concluded that 1:2 biomass/water ratio (spent coffee grounds as received) and no chemicals added during HTC with further activation in CO2 at 800°C for 1 h are suitable conditions to produce the CO2 adsorbents. In addition, the response surface methodology (RSM) successfully evaluated the combined effect of HTC temperature and dwell time, to maximize the CO2 capture capacity within the experimental region. Both the lowest temperature and dwell time (120°C, 3 h) resulted in the maximum CO2 capture capacity (2.95 wt.%). Two activated carbons (ACs) were then produced: one via hydrothermal carbonization optimized by means of response surface methodology (RSM) followed by CO2 activation (HC‐Co) and the other one by single‐step CO2 activation as described in the Group's patent ES2526259 (AC‐Co). Analysis of the features and performances of the two ACs revealed superior chemical and textural characteristics on HC‐Co for CO2 adsorption under post‐combustion capture conditions; HTC process is the sole responsible of this enhancement. Moreover, the proposed methodology to produce CO2 adsorbents from spent coffee grounds represents a more energy‐efficient approach. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

Biomass/Biochar carbon materials for CO2 capture and sequestration by cyclic adsorption processes: A review and prospects for future directions

“…Among different evaluated sorbents in the recent decades, carbonbased materials are highly attractive one for gas capture and storage for several reasons [14,17,18]. First, these materials can be considered as low-cost sorbents, prepared from a broad sustainable sources including animal wastes [37], agricultural residues [34], plant wastes [38,39], coals [40], as well as pyrolysis of fly ash [41], raw biomass [42,43] and carbon containing resins [44]. Also, activated carbons are hydrophobic materials, which is one of the key qualities of these samples in comparison with most of zeolites and MOFs to overcome the moisture effects in the gas purification studies [38,39,45].…”

“…First, these materials can be considered as low-cost sorbents, prepared from a broad sustainable sources including animal wastes [37], agricultural residues [34], plant wastes [38,39], coals [40], as well as pyrolysis of fly ash [41], raw biomass [42,43] and carbon containing resins [44]. Also, activated carbons are hydrophobic materials, which is one of the key qualities of these samples in comparison with most of zeolites and MOFs to overcome the moisture effects in the gas purification studies [38,39,45]. In addition, generally, gas adsorption onto the porous carbons has a lower heat of adsorption than other sorbents [17], which nominates this adsorbent as an excellent candidate for cyclic adsorption processes [46].…”

Standing out the key role of ultramicroporosity to tailor biomass-derived carbons for CO2 capture

“…The latter was used after mechanical extraction of high-value oil. The synthesis procedure of the biomassbased carbons has been detailed elsewhere [30,31]. Basically, they were produced by simultaneous carbonization/activation under CO2.…”

Study of the Potential Uses of Hydrochar from Grape Pomace and Walnut Shells Generated from Hydrothermal Carbonization as an Alternative for the Revalorization of Agri-Waste in Chile

“…The motivation for this research lies in the exploration for potential uses of the residues produced from grape pomace and walnut shells, two of Chile's important NCRE resources. Through thermochemical conversion and hydrothermal carbonization (HTC), grape pomace and walnut shells become hydrochar, which has several uses, such as soil amendment, energy as pellets, or low-cost adsorbents [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20].…”