Qiao Hong-Tao, Qiao Yong-Sheng, Luo Xiao-Hang, Zhao Bao-Wei, Cai Qiu-Ying
Institute of Applied Chemistry, Department of Chemistry, Xinzhou Teachers University Xinzhou 034000 China
School of Environmental and Municipal Engineering, Lanzhou Jiaotong University Lanzhou 730070 China
RSC Adv. 2021 Nov 29;11(60):38273-38282. doi: 10.1039/d1ra05636k. eCollection 2021 Nov 23.
The objective of this study is to investigate the qualitative mechanisms of Zn adsorption on carp biochars (CMB) produced from dead carp at different temperatures (450-650 °C) and their quantitative contribution. The pseudo second order kinetic model and the Langmuir model could fit the kinetic and isothermal adsorption data well, respectively. The intra-particle diffusion was the main rate-limiting step but not the only rate-limiting step. The maximum adsorption capacity obtained from the Langmuir model for CMB650 was 87.7 mg g which was greater than those of other biochars. Precipitation with minerals, ion exchange, and complexation with functional groups (OFGs) were the main adsorption mechanisms. Quantum chemistry calculations confirmed that the functional groups (, hydroxyl, carboxyl and C[double bond, length as m-dash]C) tended to bind with Zn more strongly than with Ca and Mg, because the structure of the complex formed by the former was more stable. The contribution of different adsorption mechanisms varied with the pyrolysis temperature to prepare biochar. With increasing pyrolysis temperature, the contribution of the interaction between Zn and the minerals increased from 46.4% to 84.7%, while that of complexation with OFGs decreased from 41.7% to 4.7%. Overall, the mechanism of Zn adsorption on CMB450 was dominated by complexation with OFGs and exchange with cations (accounting for 73.2%), while the mechanisms on CMB650 were dominated by the interaction with minerals. In view of the total adsorption capacity, 650 °C was the optimized pyrolysis temperature for CMB preparation and adsorption treatment of Zn-contaminated water. These results are useful for screening effective biochars as engineered sorbents to treat Zn-containing wastewater.
本研究的目的是探究在不同温度（450 - 650°C）下由死鲤鱼制备的鲤鱼生物炭（CMB）对锌的吸附定性机制及其定量贡献。伪二级动力学模型和朗缪尔模型分别能很好地拟合动力学和等温吸附数据。颗粒内扩散是主要的限速步骤，但不是唯一的限速步骤。由朗缪尔模型得出的CMB650的最大吸附容量为87.7 mg/g，大于其他生物炭。与矿物质沉淀、离子交换以及与官能团（OFGs）络合是主要的吸附机制。量子化学计算证实，官能团（羰基、羟基、羧基和C = C）与锌的结合倾向比与钙和镁更强，因为前者形成的络合物结构更稳定。不同吸附机制的贡献随制备生物炭的热解温度而变化。随着热解温度升高，锌与矿物质之间相互作用的贡献从46.4%增加到84.7%，而与OFGs络合的贡献从41.7%降至4.7%。总体而言，CMB450对锌的吸附机制以与OFGs络合和与阳离子交换为主（占73.2%），而CMB650的吸附机制以与矿物质相互作用为主。鉴于总吸附容量，650°C是制备CMB并用于吸附处理含锌废水的最佳热解温度。这些结果有助于筛选有效的生物炭作为工程吸附剂来处理含锌废水。
