Competitive adsorption behaviour and mechanisms of cadmium, nickel and ammonium from aqueous solution by fresh and ageing rice straw biochars

• Published in: Bioresource technology 2020-05, Vol.303, p.122853-122853, Article 122853
• Main Authors: Deng, Yiyi, Huang, Shuang, Dong, Caiqin, Meng, Zhuowen, Wang, Xiugui
• Format: Article
• Language: English
• Subjects: Adsorption; Ammonium; Ammonium Compounds; Biochar; Cadmium; Charcoal; Mechanism; Nickel; Oryza
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2020.122853

[Display omitted] •The adsorption sites for Cd2+, Ni2+ and NH4+ on the biochars were competitive.•Cation exchange and mineral co-precipitation dominated Cd2+ and Ni2+ adsorption.•The other potential mechanisms dominated NH4+ adsorption.•Competition between Cd2+ and Ni2+ decreased cation exchange mechanism.•Biochar aging increased the contributions of surface complexation mechanism. In this study, competitive adsorption behaviour and mechanisms of Cd2+, Ni2+ and NH4+ by fresh and artificially ageing biochars produced from rice straw at 400 and 700 °C (RB400, RB700, HRB400 and HRB700) were investigated. Cd2+ competed with Ni2+ and NH4+ for the overlapped adsorption sites on the biochars. For Cd2+ and Ni2+ adsorption, cation exchange (Qci) and mineral co-precipitation (Qcp) were the primary mechanisms for the low-temperature and high-temperature biochars, respectively. However, the other potential mechanisms (Qco) made the greatest contributions to NH4+ adsorption (>60%). Cd2+ and Ni2+ competition increased the proportions of mineral co-precipitation (Qcp) and other potential mechanisms (Qco) but decreased that of cation exchange (Qci) mechanism. Biochar ageing increased the contribution of surface complexation (Qcf) mechanism, especially for the low-temperature biochars. This study indicated that biochar aging and types and states of adsorbates should be considered when biochars were applied to remove contaminants.