LI Xinyi^{1, 3}, LU Lifang¹, MA Chunya^1,2, LEI Mingjing¹, ZHU Jian¹

(1. College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China;2. Ecological Environmental Protection Agency of Longyou Branch, Quzhou 324400, China;3. Water Affairs Department of Changling Branch, China Petrochemical Corporation, Yueyang 414000, China)

Abstract: The biochar was prepared by thermal decomposition method at 300, 500, and 700 ℃ using wetland plants as raw materials including Canna indica L (MBC), Thalia dealbata Fraser (ZBC) and Cyperus involucratus Rottboll (HBC). The physicochemical properties of the biochar were characterized by automatic elemental analyzer, scanning electron microscope and infrared spectroscopy, and the adsorption characteristics of cadmium on the biochar were systematically studied by static adsorption method. The results show that the pyrolysis temperature has a great influence on the physicochemical properties, surface morphology and mineral composition of biochar. The biochar that prepared at medium temperature (500 ℃) and high temperature (700 ℃) pyrolysis temperature has better cadmium adsorption capacity than the low temperature (300 ℃). The pyrolyzed biochar on 500 ℃ has the highest adsorption capacity, its average adsorption capacity for Cd²⁺ reaches 96.00 mg·g^-1, the extreme value reaches 108.28 mg·g^-1, and the adsorption capacity from large to small is ZBC, MBC, HBC. The adsorption equilibrium time of pyrolyzed plant-based biochar on 500 ℃ to Cd²⁺ is about 30 mins. The appropriate dosage and larger solution pH, initial ion concentration and reaction temperature have positive effects on the Cd²⁺ adsorption. The adsorption process of Cd²⁺ by biochar is in line with the Freundlich isothermal adsorption model and quasi-two-stage kinetic model, and it belongs to preferential adsorption. The higher pyrolysis temperature can promote the aromatization of biochar, improve the pore structure and increase the specific surface area, which in turn enhances the activity of biochar. The biochar pyrolyzed at medium and high temperature has better adsorption capacity for cadmium.

Keywords: wetland plants; biochar; pyrolysis temperature; cadmium; adsorption

Received： 2022-04-16，Revised:2022-05-12，Online：2022-11-19 17:53。

Funding Project：湖南省重点研发计划项目，编号：2017SK2273、2019SK2191；湖南省高校创新平台开放基金项目，编号：19K107；湖南省教育厅科学研究项目，编号：19C1900。

First Author：李心怡(1998—)，女，硕士研究生，研究方向为土壤污染修复。E-mail： 891253424@qq.com。

Corresponding Author：雷明婧(1987—)，女，实验师，硕士，研究方向为环境功能材料的制备与应用。E-mail： casper10262003@yahoo.com.cn。