Vegetation has successfully been used for remediation of heavy-metal-contaminated soils (phytoremediation). The heavy-metal-rich biomass after phytoremediation can be processed by pyrolysis, achieving bioenergy production and pollutant control. The pretreatment of the heavy-metal-rich biomass prior to pyrolysis, as an emerging factor, needs to be investigated. For this purpose, heavy-metal-rich biomass obtained from phytoremediation was engineered by impregnating with four phosphates (KH₂PO₄, K₂HPO₄, NaH₂PO₄, and Na₂HPO₄) prior to pyrolysis in the temperature range of 300–700 °C. The untreated (control) and water-wash-treated biomass were employed as references. Results showed that impregnated K₂HPO₄ and Na₂HPO₄ catalyzed the pyrolysis process, reducing the temperature for the highest mass loss rate from 343 °C in the control to ∼306 °C. The heavy metals enriched in the control also catalyzed the pyrolysis process. The bio-oils produced from the phosphate pretreatments contained a higher proportion of phenolic compounds while lower ketones compared to the control. Notably, upon the phosphate pretreatment, the heavy metal recoveries in the biochars at 500 °C were significantly increased, with more than 80% of As and more than 90% of Pb and Zn sequestrated in the solid products. This study showed that the application of phosphates as the pretreatment method catalyzed the pyrolysis of the heavy-metal-rich biomass, enhanced the heavy metal recovery in biochars, and thus provided a safe and value-added way to the phytoremediation–pyrolysis scheme.

中文翻译：

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磷酸盐预处理对重金属污染生物质热解产物性质的影响

植被已成功用于修复重金属污染的土壤（植物修复）。植物修复后富含重金属的生物质可以通过热解进行处理，从而实现生物能的产生和污染物的控制。作为新兴因素，需要研究热解之前富含重金属的生物质的预处理。为此，通过用四种磷酸盐（KH ₂ PO ₄，K ₂ HPO ₄，NaH ₂ PO ₄和Na ₂ HPO ₄浸渍）对从植物修复获得的富含重金属的生物质进行工程处理。），然后在300–700°C的温度范围内进行热解。将未处理的（对照）和水洗处理的生物质用作参考。结果表明，浸渍的K ₂ HPO ₄和Na ₂ HPO ₄催化热解过程，将最高质量损失速率的温度从对照组的343°C降低到306°C。对照中富集的重金属也催化了热解过程。与对照相比，由磷酸盐预处理产生的生物油含有较高比例的酚类化合物，而酮含量较低。值得注意的是，在进行磷酸盐预处理后，生物炭中500℃下的重金属回收率显着提高，固体产品中的砷含量超过80％，铅和锌的铅含量超过90％。这项研究表明，磷酸盐作为预处理方法可催化富含重金属的生物质的热解，提高了生物炭中重金属的回收率，从而为植物修复-热解方案提供了安全和增值的途径。