Biochar has exceeded expectations for immobilizing heavy metals (HMs), but the potential ecological risks of its long-term burial in soil limit its practical application on a large scale. To address this challenge, a novel separable water-hardened magnetic composite biochar sphere (WMBCS) was prepared and applied to remediate agricultural soils contaminated with Cd, Pb, and As. The first application of WMBCS is simultaneously effective in removing Cd (3.2–12.7%), Pb (3.3–13.1%), and As (5.0–25.6%) from soil, and the removal rates are enhanced with increasing soil moisture, application dose and incubation time. WMBCS is more efficient for removing Cd and Pb in mildly contaminated alkaline soils than in heavily contaminated acidic soils. Compared with other regeneration methods, shaking and ultrasound-assisted EDTA-2Na efficiently elutes HMs with a dissolution efficiency of over 75% within 4 h, accompanied by the lowest rate of mass loss (7.6%) and Fe leaching (475.1 mg kg). After 5 rounds of successive cyclic remediation, WMBCS exhibits high adsorption efficiency (26.5–30.6% for Cd, 25.4–30.2% for Pb, and 30.2–41.0% for As), magnetic separation efficiency (98.8–99.8%) and regeneration efficiency (92.3–95.4%). The main mechanisms involved in the adsorption and regeneration of WMBCS include ion exchange and chelation. WMBCS is an economical and eco-friendly material with vast unexplored potential for use in agriculture.

中文翻译：

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水硬化磁性复合生物炭球的回收与再生用于去除污染土壤中的多种重金属

生物炭在固定重金属（HMs）方面超出了预期，但其长期埋藏在土壤中的潜在生态风险限制了其大规模的实际应用。为了应对这一挑战，制备了一种新型可分离水硬化磁性复合生物炭球（WMBCS），并将其应用于修复受镉、铅和砷污染的农业土壤。首次施用 WMBCS 可同时有效去除土壤中的 Cd (3.2–12.7%)、Pb (3.3–13.1%) 和 As (5.0–25.6%)，且去除率随着土壤湿度、施用剂量的增加而增强和孵化时间。 WMBCS 在轻度污染的碱性土壤中比在重度污染的酸性土壤中更有效地去除 Cd 和 Pb。与其他再生方法相比，振荡和超声辅助的 EDTA-2Na 可有效洗脱 HMs，4 小时内溶解效率超过 75%，质量损失率最低（7.6%），Fe 浸出率最低（475.1 mg·kg）。经过5轮连续循环修复后，WMBCS表现出较高的吸附效率（Cd吸附率为26.5-30.6%，Pb吸附率为25.4-30.2%，As吸附率为30.2-41.0%）、磁分离效率（98.8-99.8%）和再生效率（ 92.3–95.4%）。 WMBCS 吸附和再生的主要机制包括离子交换和螯合。 WMBCS 是一种经济且环保的材料，在农业方面具有巨大的未开发潜力。