Enhanced Adsorption of Tetracycline by Thermal Modification of Coconut Shell-Based Activated Carbon

Do-Gun Kim; Shinnee Boldbaatar; Seok-Oh Ko

doi:10.3390/ijerph192113741

Enhanced Adsorption of Tetracycline by Thermal Modification of Coconut Shell-Based Activated Carbon

Int J Environ Res Public Health. 2022 Oct 22;19(21):13741. doi: 10.3390/ijerph192113741.

Authors

Do-Gun Kim¹, Shinnee Boldbaatar¹, Seok-Oh Ko²

Affiliations

¹ Department of Environmental Engineering, Sunchon National University, 255 Jungang-ro, Suncheon 57922, Korea.
² Department of Civil Engineering, Kyung Hee University, 1732, Deakyungdaero, Yongin 17104, Korea.

Abstract

Tetracycline (TC) is one of the most frequently detected antibiotics in various water matrices, posing adverse effects on aquatic ecosystems. In this study, coconut shell-based powdered activated carbon (PAC) was thermally modified under various temperatures to enhance TC adsorption. The PAC subjected to 800 °C (PAC800) showed the best TC adsorption. PAC and PAC800 were characterized using N₂ adsorption/desorption isotherm, X-ray photoelectron spectroscopy, Raman spectroscopy, XRD, Boehm titration, and zeta potential analyses. Increases in the specific surface area, C/O ratio, C=O, surface charge, basic groups, and the number of stacked graphene layers along with a decrease in structural defects were observed for PAC800 compared to PAC. The TC adsorption was significantly improved for PAC800 compared to that of PAC, which is attributable to the enhanced electrostatic attraction and π-π EDA interactions induced by the changes in the properties. The Freundlich isotherm was the best fit indicating the heterogeneous nature, and the Freundlich constant of PAC and PAC800 increased from 85.8 to 119.5 and 132.1 to 178.6 (mg/g)‧(L/mg)^1/n, respectively, when the temperature was increased from 296.15 to 318.15 K. The kinetics were well described by the pseudo-second-order adsorption model and the rate constant of PAC and PAC800 increased from 0.80 to 1.59 and from 0.72 to 1.29 × 10^-3 g/mg‧min, respectively, as the temperature was increased. The activation energy of PAC and PAC800 was 23.7 and 19.6 J/mol, respectively, while the adsorption enthalpy was 196.7 and 98.5 kJ/mol, respectively, indicating endothermic nature. However, it was suggested that TC adsorption onto PAC800 was more favorable and was more contributed to by physisorption than that onto PAC. These results strongly suggest that the properties, adsorption capacity, and adsorption mechanisms of carbonaceous adsorbents can be significantly changed by simple thermal treatment. More, the results provide valuable information about the design of carbonaceous adsorbents with better performance where the structures and functional groups, which positively affect the adsorption, must be improved.

Keywords: activated carbon; adsorption; antibiotic; thermal modification; thermodynamics.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adsorption
Anti-Bacterial Agents / chemistry
Charcoal / chemistry
Cocos
Ecosystem
Hydrogen-Ion Concentration
Kinetics
Tetracycline
Thermodynamics
Water Pollutants, Chemical* / chemistry
Water Purification* / methods

Substances

Charcoal
Water Pollutants, Chemical
Tetracycline
Anti-Bacterial Agents

Grants and funding

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT) (No.2021R1F1A1064004). This work was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2022R1A2B5B02001584).