Dataset Information

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds.

ABSTRACT: A valorization process of spent coffee grounds (SCG) was studied. Thus, a two-stage process, the first stage of polyphenols extraction and synthesis of a carbonaceous precursor and a subsequent stage of obtaining activated carbon (AC) by means of a carbonization process from the precursor of the previous stage, was performed. The extraction was carried out with a hydro-alcoholic solution in a pressure reactor, modifying time, temperature and different mixtures EtOH:H₂O. To optimize the polyphenols extraction, a two-level factorial experimental design with three replicates at the central point was used. The best results were obtained by using a temperature of 80?°C during 30?min with a mixture of EtOH:H₂O 50:50 (v/v). Caffeine and chlorogenic acid were the most abundant compounds in the analysed extracts, ranging from 0.09 to 4.8?mg?g^-1 and 0.06 to 9.7?mg?g^-1, respectively. Similarly, an experimental design was realized in order to analyze the influence of different variables in the AC obtained process (reaction time, temperature and KOH:precursor ratio). The best results were 1?h, 850?°C, and a mixture of 2.5:1. The obtained activated carbons exhibit a great specific surface (between 1600?m²?g^-1 and 2330?m²?g^-1) with a microporous surface. Finally, the adsorption capacity of the activated carbons was evaluated by methylene blue adsorption.

SUBMITTER: Ramon-Goncalves M

PROVIDER: S-EPMC6881328 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds.

Ramón-Gonçalves Marina M Alcaraz Lorena L Pérez-Ferreras Susana S León-González María Eugenia ME Rosales-Conrado Noelia N López Félix A FA

Scientific reports 20191127 1

A valorization process of spent coffee grounds (SCG) was studied. Thus, a two-stage process, the first stage of polyphenols extraction and synthesis of a carbonaceous precursor and a subsequent stage of obtaining activated carbon (AC) by means of a carbonization process from the precursor of the previous stage, was performed. The extraction was carried out with a hydro-alcoholic solution in a pressure reactor, modifying time, temperature and different mixtures EtOH:H<sub>2</sub>O. To optimize th ...[more]

PMID: 31776434

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Project description:Torrefaction of biomass is a promising thermochemical pretreatment technique used to upgrade the properties of biomass to produce solid fuel with improved fuel properties. A comparative study of the effects of torrefaction temperatures (200, 250, and 300 °C) and residence times (0.5 and 1 h) on the quality of torrefied biomass samples derived from spent coffee grounds (SCG) and coffee husk (CH) were conducted. An increase in torrefaction temperature (200-300 °C) and residence time (0.5-1 h) for CH led to an improvement in the fixed carbon content (17.9-31.8 wt %), calorific value (18.3-25 MJ/kg), and carbon content (48.5-61.2 wt %). Similarly, the fixed carbon content, calorific value, and carbon content of SCG rose by 14.6-29 wt %, 22.3-30.3 MJ/kg, and 50-69.5 wt %, respectively, with increasing temperature and residence time. Moreover, torrefaction led to an improvement in the hydrophobicity and specific surface area of CH and SCG. The H/C and O/C atomic ratios for both CH- and SCG-derived torrefied biomass samples were in the range of 0.93-1.0 and 0.19-0.20, respectively. Moreover, a significant increase in volatile compound yield was observed at temperatures between 250 and 300 °C. Maximum volatile compound yields of 11.9 and 6.2 wt % were obtained for CH and SCG, respectively. A comprehensive torrefaction model for CH and SCG developed in Aspen Plus provided information on the mass and energy flows and the overall process energy efficiency. Based on the modeling results, it was observed that with increasing torrefaction temperature to 300 °C, the mass and energy yield values of the torrefied biomass samples declined remarkably (97.3% at 250 °C to 67.5% at 300 °C for CH and 96.7% at 250 °C to 75.1% at 300 °C for SCG). The SCG-derived torrefied biomass tested for CO2 adsorption at 25 °C had a comparatively higher adsorption capacity of 0.38 mmol/g owing to its better textural characteristics. SCG would need further thermal treatment or functionalization to tailor the surface properties to attract more CO2 molecules under a typical post-combustion scenario.

Dataset Information

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds.

Publications

Extraction of polyphenols and synthesis of new activated carbon from spent coffee grounds.

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