Preparation of mesoporous activated carbon from defective coffee beans for adsorption of fresh whey proteins

Giovanni Aleixo Batista,Isabelle Cristina Oliveira Neves,Willian De Paula Gomes,Lizzy Ayra Alcântara Veríssimo,Maria Letícia Martins Silva,Jenaina Ribeiro Soares,Paula Chequer Gouveia Mól,Jaime Vilela De Resende

doi:10.4025/actascitechnol.v42i1.45914

Giovanni Aleixo Batista, Isabelle Cristina Oliveira Neves + Show 6 more

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https://doi.org/10.4025/actascitechnol.v42i1.45914

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Abstract

Whey protein has high biological value and functional properties. Therefore, it is necessary to develop methods to recover this valuable protein and minimize the environmental impacts. Adsorptive processes using alternative adsorbents from agroindustrial waste increase the number of alternatives for adequate final disposal of the waste and add value. The aim of this study was to develop a mesoporous activated carbon (AC) from defective coffee beans (DCB) for the adsorption of fresh whey protein. The morphological structure of the adsorbent produced was characterized, and both Raman spectroscopy, FTIR and thermal analyses were performed; and the effect of pH on the adsorption capacity (q, mg g-1) was evaluated. The characterization showed that: the AC exhibited a porous size between 33 and 43 Å, corresponding to mesoporous materials; the crystallite size (La) of AC was estimated at 9.31 ± 0.14 nm; the highest adsorption capacity value (239.1781 mg g-1) was achieved at pH 2.5 and 25ºC; and the point of zero charge of the adsorbent was at pH 2.0. The pseudo first-order model fit best to the experimental results (R2 > 0.99) of whey protein adsorption onto activated carbon, and the Langmuir model was the most appropriate to represent the experimental data, with a maximum adsorption capacity of 378.4380 mg g-1, demonstrating the potential of AC obtained from DCB to adsorb fresh whey protein.

Highlights

The solid matrix is treated with a chemical compound that remains impregnated in the precursor material (PM), subsequently subjected to carbonization (Liou, 2010; Pereira et al, 2014)
After chemical activation and carbonization of the precursor, the activated carbon (AC) obtained from defective coffee beans (DCB) presented a low ash content
In this study La for activated carbons was estimated by a linear correlation (Equation 9), which applies to a wide range of carbon nanostructures (Cançado et al, 2006; Ribeiro-Soares et al, 2013):

Summary

Introduction

Activated carbon presents a high specific surface area that is related to the target molecule to be adsorbed. Its great chemical and mechanical stability, in addition to the variety of possible functional groups existent on the carbon surface, enables it to be widely utilized instead of the classic adsorbents such as silica gel, activated alumina and molecular sieves (Pereira et al, 2014; Yang & Qiu, 2011). The solid matrix is treated with a chemical compound that remains impregnated in the precursor material (PM), subsequently subjected to carbonization (Liou, 2010; Pereira et al, 2014). The presence of large pores makes the adsorbent suitable for adsorption of larger biomolecules (Andrade et al, 2018; Liou, 2010; Pereira et al, 2014; Yang & Qiu, 2011)

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