Enhancing Cd(II) adsorption on rice straw biochar by modification of iron and manganese oxides

• Published in: Environmental pollution (1987) 2022-05, Vol.300, p.118899-118899, Article 118899
• Main Authors: Tan, Wen-Tao, Zhou, Hang, Tang, Shang-Feng, Zeng, Peng, Gu, Jiao-Feng, Liao, Bo-Han
• Format: Article
• Language: English
• Subjects: Adsorption; Cadmium; Cadmium - analysis; Characterization analysis; Charcoal - chemistry; Fe–Mn oxide-modified biochar; Iron; Kinetics; Manganese; Oryza - chemistry; Oxides - chemistry; Wastewater; Water Pollutants, Chemical - analysis
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.118899

Metal oxide-modified biochar showed excellent adsorption performance in wastewater treatment. Iron nitrate and potassium permanganate were oxidative modifiers through which oxygen-containing groups and iron–manganese oxides could be introduced into biochar. In this study, iron–manganese (Fe–Mn) oxide-modified biochar (BC-FM) was synthesized using rice straw biochar, and the adsorption process, removal effect, and the mechanism of cadmium (Cd) adsorption on BC-FM in wastewater treatment were explored through batch adsorption experiments and characterization (SEM, BET, FTIR, XRD, and XPS). Adsorption kinetics showed that the maximum adsorption capacity of BC-FM for Cd(II) was 120.77 mg/g at 298 K, which was approximately 1.5–10 times the amount of adsorption capacity for Cd(II) by potassium-modified or manganese-modified biochar as mentioned in the literature. The Cd(II) adsorption of BC-FM was well fit by the pseudo-second-order adsorption and Langmuir models, and it was a spontaneous and endothermic process. Adsorption was mainly controlled via a chemical adsorption mechanism. Moreover, BC-FM could maintain a Cd removal rate of approximately 50% even when reused three times. Cd(II) capture by BC-FM was facilitated by coprecipitation, surface complexation, electrostatic attraction, and cation-π interaction. Additionally, the loaded Fe–Mn oxides also played an important role in the removal of Cd(II) by redox reaction and ion exchange in BC-FM. The results suggested that BC-FM could be used as an efficient adsorbent for treating Cd-contaminated wastewater. [Display omitted] •A highly adsorptive Fe–Mn oxide-modified biochar was prepared using Fe(NO)3 and KMnO4.•The form and valence of Fe2O3 and Mn2O3 in BC-FM changed during Cd(II) adsorption.•BC-FM showed high removal capacity even reused three times (45.4%–66.2%).•Cu and Zn inhibited Cd(II) adsorption by competing for adsorption sites.