Abstract：
Chemical stabilization is frequently used to stabilize lead (Pb) or arsenate (As), but faces challenges in Pb-As co-contaminated soils because of the antagonistic reactions between chemical stabilizers and contaminants. In this work, we innovated an effective and cost-efficient stepwise steam flash heating (SSFH) strategy to simultaneously immobilize Pb and As, and unraveled the underlying mechanisms. The combination of 1.5% Ca(H2PO4)2 and 2% Fe2(SO4)3 only decreased 1.99% Pb by toxicity characteristic leaching procedure (TCLP-Pb) but increased 17.8% of TCLP-As due to the antagonistic effects. SSFH with Ca(H2PO4)2 in the first step and Fe2(SO4)3 in the second step achieved the minimal TCLP-Pb and TCLP-As of 0.778 and 0.327 mg/L, respectively. It also reduced 69.8% of leachable As in 100-year acid rain simulation, indicating a favorable long-term stabilization performance. Additionally, SSFH approach reduced 43.2% stabilizer dosage and 14.9% cost. X-ray absorption near edge structure (XANES) documented that the stepwise SFH promoted the transformation of Pb(NO3)2 and NaAsO2/NaAsO3/As2O3/As2O5 into stable Pb3(PO4)2 and FeAsO4, preventing the formation of AsO43- and FePO4. Our findings proved the state-of-the-art SSFH approach and unraveled its mechanisms to stabilize Pb and As co-contamination in soils, offering a green and sustainable remediation alternative for the management of heavy metal contaminated sites. ENVIRONMENTAL IMPLICATION: A novel stepwise SFH approach can be applied to overcome the stabilizer antagonist effects by separately immobilizing Pb and As in two sequential steps. It also decreased 43.2% of stabilizer dosage and 14.9% of cost comparing to conventional chemical stabilization. This approach can be used for other metal co-contaminated soils facing similar antagonistic challenges, and our work raises a state-of-the-art solution for cost-effective, green and sustainable remediation practices.
摘要：
化学稳定化通常用于稳定铅（Pb）或砷酸盐（As），但是由于化学稳定剂和污染物之间的拮抗反应，在Pb-As共污染土壤中面临挑战。在这项工作中,我们创新了一种有效且具有成本效益的逐步蒸汽闪蒸加热（SSFH）策略，以同时固定Pb和As，并揭示了潜在的机制。通过毒性特征浸出程序（TCLP-Pb），1.5％Ca（H2PO4）2和2％Fe2（SO4）3的组合仅减少了1.99％Pb，但由于拮抗作用，TCLP-As增加了17.8％。在第一步中使用Ca（H2PO4）2和在第二步中使用Fe2（SO4）3的SSFH实现了0.778和0.327mg/L的最低TCLP-Pb和TCLP-As，分别。在100年酸雨模拟中，它还减少了69.8%的可浸出砷，表明良好的长期稳定性能。此外,SSFH方法降低了43.2%的稳定剂用量和14.9%的成本。X射线吸收近边缘结构（XANES）证明，逐步SFH促进了Pb（NO3）2和NaAsO2/NaAsO3/As2O3/As2O5向稳定的Pb3（PO4）2和FeAsO4的转化，阻止了AsO43-和FePO4的形成。我们的发现证明了最先进的SSFH方法，并揭示了其稳定土壤中Pb和As共污染的机制，为重金属污染场地的管理提供绿色和可持续的修复替代方案。环境意义：一种新颖的逐步SFH方法可以通过在两个连续步骤中分别固定Pb和As来克服稳定剂拮抗剂的作用。与常规化学稳定化相比，它还降低了43.2%的稳定剂用量和14.9%的成本。这种方法可用于面临类似拮抗挑战的其他金属共污染土壤，我们的工作提出了一个最先进的解决方案，绿色和可持续的补救做法。
