Preparation of Adsorbent Materials from Rice Husk via Hydrothermal Carbonization: Optimization of Operating Conditions and Alkali Activation

Jhosué Naranjo, Evelyn Juiña, Carlos Loyo, Michelle Romero, Karla Vizuete, Alexis Debut, Sebastian Ponce () and Herman A. Murillo ()
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Jhosué Naranjo: Department of Chemical Engineering, Universidad San Francisco de Quito USFQ, Diego de Robles s/n y Avenida Interoceánica, Quito 170901, Ecuador
Evelyn Juiña: Department of Chemical Engineering, Universidad San Francisco de Quito USFQ, Diego de Robles s/n y Avenida Interoceánica, Quito 170901, Ecuador
Carlos Loyo: School of Chemical Sciences and Engineering, Yachay Tech University, Hda. San José s/n y Proyecto Yachay, Urcuquí 100119, Ecuador
Michelle Romero: Instituto de Investigación Geológico y Energético, Av. de la República E7-263, Quito 170518, Ecuador
Karla Vizuete: Centro de Nanociencia y Nanotecnología, Universidad de las Fuerzas Armadas ESPE, Av. General Rumiñahui s/n y Ambato, Sangolquí 171103, Ecuador
Alexis Debut: Centro de Nanociencia y Nanotecnología, Universidad de las Fuerzas Armadas ESPE, Av. General Rumiñahui s/n y Ambato, Sangolquí 171103, Ecuador
Sebastian Ponce: Department of Chemical Engineering, Universidad San Francisco de Quito USFQ, Diego de Robles s/n y Avenida Interoceánica, Quito 170901, Ecuador
Herman A. Murillo: Department of Chemical Engineering, Universidad San Francisco de Quito USFQ, Diego de Robles s/n y Avenida Interoceánica, Quito 170901, Ecuador

Resources, 2023, vol. 12, issue 12, 1-14

Abstract: Hydrothermal carbonization (HTC) of rice husk was optimized in terms of the adsorption capacity at equilibrium (q e ) and hydrochar mass yield (MY). The studied variables were reaction temperature, residence time, and biomass-to-water ratio by means of response surface methodology. In both cases, reaction temperature resulted the most significant parameter promoting high q e values at higher temperatures when treating methylene blue (MB) as the target pollutant. Nevertheless, MY was low (~40%) when focusing on a possible industrial application. Hence, maximizing q e and MY simultaneously by optimization of multiple responses emerges as a promising solution to improve MY values (>60%) with no significant differences regarding the q e response. Furthermore, additional activation was conducted on optimal hydrochars to further investigate the enhancement of q e . As a result, no statistical differences between non-modified and activated hydrochars were observed for q e ; however, the pseudo-second-order constant (k 2 ) seemed to be increased after alkali activation, mainly due to a larger surface area. Non-modified and activated hydrochars were characterized via SEM, FTIR, XRD, and BET, resulting in two significant effects contributing to MB adsorption: increased surface area and functionalized hydrochar surface. Consequently, this work provides valuable insights on subsequent application of this HTC optimization scheme at an industrial scale.

Keywords: hydrothermal carbonization; rice husk; process optimization; adsorbents; alkali activation (search for similar items in EconPapers)
JEL-codes: Q1 Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2023
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