Functionalization of pine sawdust biochars with Mg/Al layered double hydroxides to enhance adsorption capacity of synthetic azo dyes: Adsorption mechanisms and reusability

Jonggu Kim; Guen-Hyeok Bak; Da-Young Yoo; Young-In Lee; Yong-Gu Lee; Kangmin Chon

doi:10.1016/j.heliyon.2023.e14142

Functionalization of pine sawdust biochars with Mg/Al layered double hydroxides to enhance adsorption capacity of synthetic azo dyes: Adsorption mechanisms and reusability

Heliyon. 2023 Feb 28;9(3):e14142. doi: 10.1016/j.heliyon.2023.e14142. eCollection 2023 Mar.

Authors

Jonggu Kim^{1

2}, Guen-Hyeok Bak², Da-Young Yoo², Young-In Lee², Yong-Gu Lee², Kangmin Chon^{1

2}

Affiliations

¹ Department of Integrated Energy and Infra System, Kangwon National University, Kangwondaehak-gil, 1, Chuncheon-si, Gangwon-do, 24341, Republic of Korea.
² Department of Environmental Engineering, College of Engineering, Kangwon National University, Kangwondaehak-gil, 1, Chuncheon-si, Gangwon-do, 24341, Republic of Korea.

Abstract

This study determined that the adsorption of azo dyes, Methyl Orange (MO) and Sunset Yellow FCF (SYF), using the pristine pine sawdust biochar (PSB) and post-modified PSB with Mg/Al layered double hydroxides (PSB-LDH_MgAl) was examined to offer valuable information into the differences in their adsorption mechanisms. Although a lower specific surface area of PSB-LDH_MgAl (147.2 m² g^-1) than PSB (495.7 m² g^-1), LDH_MgAl were successfully functionalized on the PSB surface through co-precipitation, which was highly related to the improvements of adsorption capacity of PSB-LDH_MgAl toward MO and SYF. The MO and SYF adsorption kinetics by PSB and PSB-LDH_MgAl were confirmed to the pseudo-second-order and considered chemisorption. The adsorption capacity of MO and SYF adsorbed onto PSB-LDH_MgAl (MO = 21.8 mg g^-1, SYF = 23.6 mg g^-1) were significantly higher than that of PSB (MO = 2.2 mg g^-1, SYF = 1.6 mg g^-1). The adsorption isotherms of MO and SYF by PSB were well fitted by Freundlich isotherm, whereas the MO and SYF via PSB-LDH_MgAl were by Langmuir isotherm. Even after 3 adsorption-desorption cycles using desorbents, the PSB-LDH_MgAl remained excellent reusability (reuse efficiency: >81.2%). These findings suggest that post-modification with LDH_MgAl might accelerate the adsorption performance (i.e., electrostatic interaction) of azo dyes to PSB in water.

Keywords: Adsorption; Azo dyes; Co-precipitation; MgAl Layered double hydroxides; Pine sawdusts biochars.