Agricultural waste biochar after potassium hydroxide activation: Its adsorbent evaluation and potential mechanism

Jian Guan; Mingxin Zhu; Jun Zhou; Liwen Luo; Luiz Fernando Romanholo Ferreira; Xueying Zhang; Jiayang Liu

doi:10.1016/j.biortech.2023.129793

Agricultural waste biochar after potassium hydroxide activation: Its adsorbent evaluation and potential mechanism

Bioresour Technol. 2023 Dec:389:129793. doi: 10.1016/j.biortech.2023.129793. Epub 2023 Sep 27.

Authors

Jian Guan¹, Mingxin Zhu¹, Jun Zhou², Liwen Luo³, Luiz Fernando Romanholo Ferreira⁴, Xueying Zhang¹, Jiayang Liu⁵

Affiliations

¹ College of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, China.
² College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, China.
³ Institute of Bioresource and Agriculture, Department of Biology, Hong Kong Baptist University, Hong Kong.
⁴ Graduate Program in Process Engineering (PEP), Tiradentes University, 49032-490 Aracaju-SE, Brazil.
⁵ College of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, China; Gongda Kaiyuan Environmental Protection Technology Co., Ltd, Chuzhou 239001, China. Electronic address: jyliu@njtech.edu.cn.

PMID: 37769976
DOI: 10.1016/j.biortech.2023.129793

Abstract

The agricultural waste (Goji branch) was pyrolyzed into biochars with one-step potassium hydroxide (KOH) activation under different processing conditions. The biochars were first characterized in structural features and functional groups and then evaluated for adsorptive performance with methylene blue as a model pollutant. Different adsorption models were applied to fit the adsorption process and reveal the possible mechanisms. The adsorption capacity was found to strongly correlate (R² = 0.9642) with the surface area of the biochars, among which biochar K_50%W_29%C-700 (pyrolysis at 700 °C in the presence of 50 % KOH and 29 % water) possessed the largest surface area (1378 m²/g) and exhibited the highest adsorption capacity (769 mg/g) compared to its homologous products. Biochar K_50%W_29%C-700 also showed excellent recyclability and potent adsorption capacity toward other common organic pollutants. The results suggest that traces of water in agricultural wastes could significantly intensify the KOH-involved activation efficiency of producing porous biochar.

Keywords: Adsorption; Goji branch; Hydroxide; Methylene blue; Pyrolysis.