Enhancement of Cd(II) adsorption by rice straw biochar through oxidant and acid modifications

• Published in: Environmental science and pollution research international Vol. 28; no. 31; pp. 42787 - 42797
• Main Authors: He, Xian, Hong, Zhi-neng, Jiang, Jun, Dong, Ge, Liu, Hui, Xu, Ren-kou
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2021; Springer Nature B.V
• Subjects: Acids; Adsorption; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Cadmium; Charcoal; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Fourier transforms; Functional groups; Hydrogen peroxide; Infrared spectra; Muffle furnaces; Oxidants; Oxidizing agents; Pyrolysis; Research Article; Rice; Rice straw; Straw; Sulfuric acid; Titration; Waste Water Technology; Water Management; Water Pollution Control; H; HNO; Carboxyl functional groups; Modified biochar; SO; mixed acid; O; Cd(II) adsorption; HNO3/H2SO4 mixed acid; H2O2
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-021-13742-8

To develop high-efficient biochar adsorbents, the effects and mechanisms of oxidant modification and acid modification on Cd(II) adsorption by rice straw biochar were investigated. Three rice straws from Langxi in Anhui Province, Yingtan in Jiangxi Province, and Lianyungang in Jiangsu Province were collected to prepare biochars by anaerobic pyrolysis in a muffle furnace. Rice straw biochars were modified by 15% H 2 O 2 and 1:1 HNO 3 /H 2 SO 4 mixed acid, respectively, to obtain modified biochars. The untreated rice straw biochar and HCl-treated rice straw biochar with carbonate removed were used as controls. The functional groups on the surfaces of the biochars were qualitatively and quantitatively determined by Fourier transform infrared spectra and Boehm titration, respectively. The adsorption and desorption of Cd(II) onto and from the biochars and modified biochars were measured under various pH conditions. The results showed that oxidant modification with 15% H 2 O 2 and acid modification with 1:1 HNO 3 /H 2 SO 4 significantly increased the number of carboxyl functional groups on the surfaces of the biochars, and acid modification was more effective than oxidant modification in amplifying carboxyl functional groups on the surfaces of the biochars. The increase of surface functional groups effectively enhanced the specific adsorption of Cd(II) on the modified biochars. Therefore, both oxidant modification and acid modification enhanced the adsorption of Cd(II) on the biochars through increasing functional groups on the surfaces of the biochars.