State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology (Beijing), Beijing, 100083, China; Key Laboratory of Agro-Environment in Downstream of Yangze Plain, Ministry of Agriculture and Rural Affairs, P. R., Jiangsu, 210014, China; School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China.
School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijing, 100083, China.
Environ Res. 2024 Jul 1;252(Pt 2):118938. doi: 10.1016/j.envres.2024.118938. Epub 2024 Apr 20.
Fly ash (FA) is mainly composed of silica, alumina, and other metal oxide components, and has a positive stabilizing effect on soil heavy metals. Biochar composites produced from FA and corn stover (CS) can improve its remediation performance. Therefore, a batch of biochar composites (alkali-fused FA-CS biochars, ABs), synthesized via co-pyrolysis of CS and alkali-fused FA (AFFA) at different temperatures of 300, 500, and 700 °C (AB300-1, AB500-1, and AB700-1) and CS to AFFA mass ratios of 10:1, 10:2, and 10:5 (AB500-1, AB500-2, and AB500-5), was used to remediate lead (Pb)-contaminated soil. Compared with pristine biochars (BCs), ABs were enriched with oxygen-containing functional groups (Si-O-Si and Si-O) and aromatic structures. The ABs prepared at lower pyrolytic temperature (≤500 °C) and lower ratio of CS to AFFA (10:1) showed higher yield and stability. The contents of Toxicity Characteristic Leaching Procedure (TCLP)-extractable Pb and DTPA-CaCl-triethanolamine (DTPA)-extractable Pb were generally lower in the soils amended with ABs than BCs. Compared with other ABs such as AB300-1, AB500-2, AB500-5, and AB700-1, the soil amended with AB500-1 had lower contents of TCLP and DTPA-extractable Pb (24% reduction), exhibiting superior performance in stabilizing Pb in the soil. The gradual decrease of DTPA-extractable Pb content in the soil with increasing dosage of AB500-1 amendments suggests that AB500-1 facilitated the conversion of bioavailable Pb to the stable and less toxic residual fractions. Specifically, the highest percentage of residual fraction of Pb in soil amended with AB500-1 was 14%. Correlation analyses showed that the soil DTPA-extractable Pb content decreased with the increase of soil pH and cation-exchange capacity (CEC) value. ABs stabilize Pb in the soils mainly via electrostatic attraction, precipitation, cation-π interaction, cation exchange, and complexation. These findings provide insights for producing functionalized biochar composites from industrial waste like FA and biomass waste for remediating the soils polluted by heavy metals.
粉煤灰（FA）主要由二氧化硅、氧化铝和其他金属氧化物组成，对土壤重金属具有积极的稳定作用。由 FA 和玉米秸秆（CS）制成的生物炭复合材料可以提高其修复性能。因此，通过在不同温度（300、500 和 700°C）下共热解 CS 和碱熔 FA（AFFA）以及 CS 与 AFFA 的质量比为 10:1、10:2 和 10:5（AB300-1、AB500-1 和 AB500-5）合成了一批生物炭复合材料（碱熔 FA-CS 生物炭，ABs），用于修复 Pb 污染土壤。与原始生物炭（BCs）相比，ABs 富含含氧官能团（Si-O-Si 和 Si-O）和芳香结构。在较低的热解温度（≤500°C）和较低的 CS 与 AFFA 比例（10:1）下制备的 ABs 产率和稳定性更高。用 ABs 改良的土壤中 TCLP 可提取 Pb 和 DTPA-CaCl-三乙醇胺（DTPA）可提取 Pb 的含量通常低于 BCs。与 AB300-1、AB500-2、AB500-5 和 AB700-1 等其他 ABs 相比，用 AB500-1 改良的土壤中 TCLP 和 DTPA 可提取 Pb 的含量较低（降低 24%），在稳定土壤中的 Pb 方面表现出优异的性能。随着 AB500-1 改良剂用量的增加，土壤中 DTPA 可提取 Pb 的含量逐渐降低，表明 AB500-1 促进了生物可利用 Pb 向稳定且毒性较低的残留态的转化。具体而言，用 AB500-1 改良的土壤中 Pb 的残留态比例最高为 14%。相关性分析表明，土壤 DTPA 可提取 Pb 含量随土壤 pH 值和阳离子交换容量（CEC）值的增加而降低。ABs 通过静电吸引、沉淀、阳离子-π 相互作用、阳离子交换和络合作用稳定土壤中的 Pb。这些发现为利用 FA 等工业废物和生物质废物生产功能化生物炭复合材料，修复重金属污染土壤提供了思路。
