Key Laboratory of Watershed Non-point Source Pollution Control and Water Eco-security of Ministry of Water Resources, College of Environmental and Resources Sciences, Zhejiang University, Hangzhou 310058, China.
College of Water Resources and Architectural Engineering, Tarim University, Xinjiang 843300, China.
Sci Total Environ. 2022 Jul 10;829:154599. doi: 10.1016/j.scitotenv.2022.154599. Epub 2022 Mar 17.
Developing effective modification methods and obtaining a comprehensive understanding of adsorption mechanisms are essential for the practical application of biochars for the removal of heavy metals from solutions. In this study, rice straw was impregnated with sodium phytate and pyrolyzed at 350 °C, 450 °C, and 550 °C to synthesize modified biochars (i.e., MBC350, MBC450, and MBC550). The Cd(II) adsorption capacities and contributions of different mechanisms, including the effects of biochar-derived dissolved organic matter (BDOM), were investigated using batch sorption experiments and characterization analyses. The modification of sodium phytate promoted the pyrolysis of biomass, thereby increasing the BDOM content and aromatic structures at low and high pyrolysis temperatures, respectively. Moreover, the modification also increased the exchangeable Na and carbonate contents in the modified biochars. Compared with the raw biochars, the Cd(II) adsorption capacities of modified biochars increased by 3.3-4.3 times, and MBC550 had the highest Cd(II) adsorption capacity (126.5 mg/g), of which precipitation with minerals and interaction with π-electrons contributed 41.7% and 45.8%, respectively. However, at a lower pyrolysis temperature, the Cd(II) adsorption attributed to ion exchange and co-deposition with BDOM significantly increased, especially on MBC350 (33.9 and 12.6 mg/g, respectively). These results indicate that modification by sodium phytate effectively enhanced various adsorption mechanisms, thereby increasing the Cd(II) adsorption capacity. In addition, the contribution of co-deposition with BDOM to adsorption was unneglectable for the biochars pyrolyzed at low temperatures.
开发有效的改性方法并全面了解吸附机制对于生物炭在溶液中去除重金属的实际应用至关重要。在这项研究中，将稻草用植酸钠浸渍，然后在 350°C、450°C 和 550°C 下热解，合成改性生物炭（即 MBC350、MBC450 和 MBC550）。通过批量吸附实验和特征分析，研究了 Cd(II)吸附容量和不同机制的贡献，包括生物炭衍生的溶解有机质（BDOM）的影响。植酸钠的改性促进了生物质的热解，从而分别在较低和较高的热解温度下增加了 BDOM 的含量和芳香结构。此外，改性还增加了改性生物炭中可交换的 Na 和碳酸盐含量。与原生物炭相比，改性生物炭的 Cd(II)吸附容量增加了 3.3-4.3 倍，MBC550 具有最高的 Cd(II)吸附容量（126.5mg/g），其中沉淀矿物和与π电子相互作用分别贡献了 41.7%和 45.8%。然而，在较低的热解温度下，与 BDOM 离子交换和共沉淀引起的 Cd(II)吸附显著增加，尤其是在 MBC350 上（分别为 33.9 和 12.6mg/g）。这些结果表明，植酸钠的改性有效增强了各种吸附机制，从而提高了 Cd(II)的吸附容量。此外，对于在低温下热解的生物炭，BDOM 共沉淀对吸附的贡献不可忽视。
