Remediation of contaminated agricultural soils focused on fixing heavy metals in soils to reduce their bioavailability. However, with the influence of pH, redox potential, and microorganism in the soils, heavy metals were likely to be released from a fixed state. The study aims to investigate magnetic porous biochar spheres and their roles in in situ sorption and removal of heavy metal from the contaminated agricultural soil. The magnetic biochar spheres were prepared using alginate and FeCl₃ through a one-step gelation to obtain alginate-Fe³⁺ gel and subsequently pyrolyzed. Results of Ultraviolet–visible spectrophotometer, X-ray diffraction and Fourier transform infrared spectrometer showed the decomposition of alginate and the formation of Fe₃O₄ and FeCl₂ hydrates nanoparticles on the spheres when the spheres were pyrolyzed at 300 °C. Scanning electron microscope image showed that the CFe₃₀₀ sphere has a macro-porous structure. The CFe₃₀₀ sphere exhibited good adsorption capacity of hexavalent chromium from aqueous solution. The CFe₃₀₀ sphere decreased the bioavailable and total cadmium (II) concentrations from 1.55 ± 0.08 to 0.32 ± 0.04 mg/kg and from 2.81 ± 0.02 to 1.39 ± 0.06 mg/kg, respectively. Moreover, the CFe₃₀₀ sphere decreased bioavailable and total arsenate (V) concentrations from 1.26 ± 0.003 to 0.85 ± 0.01 mg/kg and from 60.23 ± 0.39 to 27.34 ± 0.94 mg/kg, respectively. Subsequently, addition of water into the soil induced the spheres to leave the soil and float on the surface of soil/water mixture. Thus, the magnetic biochar spheres can be much easier to separate from the soil using magnets.

受污染的农业土壤的修复工作着眼于固定土壤中的重金属以降低其生物利用度。但是，在土壤中pH值，氧化还原电势和微生物的影响下，重金属很可能从固定状态释放出来。该研究旨在研究磁性多孔生物炭球及其在原位吸附和从污染的农业土壤中去除重金属的作用。使用藻酸盐和FeCl ₃通过一步凝胶化制备磁性生物炭球，以获得藻酸盐-Fe ³⁺凝胶，然后进行热解。紫外可见分光光度计，X射线衍射和傅立叶变换红外分光光度计的结果显示藻酸盐的分解和Fe ₃的形成当球在300°C下热解时，O ₄和FeCl ₂将球上的纳米颗粒水合。扫描电子显微镜图像显示，CFe ₃₀₀球具有大孔结构。CFe ₃₀₀球对水溶液中的六价铬具有良好的吸附能力。CFe ₃₀₀球体将生物利用度和总镉（II）浓度分别从1.55±0.08降低至0.32±0.04 mg / kg和从2.81±0.02降低至1.39±0.06 mg / kg。此外，CFe ₃₀₀球体的生物利用度和总砷酸盐（V）浓度分别从1.26±0.003降至0.85±0.01 mg / kg和从60.23±0.39降至27.34±0.94 mg / kg。随后，向土壤中添加水促使球体离开土壤并漂浮在土壤/水混合物的表面上。因此，磁性生物炭球可以更容易地使用磁体与土壤分离。