Magnetization facilitates the separation and reuse of adsorbents, but significantly reduces the adsorption capacity. In this study, a double layer magnetized/functionalized biochar composite was synthesized through a hybrid post-pyrolysis magnetization which sustained and even significantly increased the adsorption capacity of microporous carbonaceous biochar (BC). The developed process included i) structural modification of biochar under ultrasound waves, ii) magnetization with magnetite (Fe₃O₄) nanoparticles, and iii) functionalization with 3-aminopropyltriethoxysilane (TES). Ultrasound irradiation exfoliates and breaks apart the irregular graphite layers of biochar, and creates new, or opens blocked, micropores, thus enhancing the BC’s porosity. For its part, TES stabilizes the magnetic nanoparticles on the biochar surface, while it participates in water decontamination through the strong chelation ability of its amino groups toward metal ions. Scanning electron microscopy demonstrated the stable and uniform distribution of Fe₃O₄ nanoparticles on the surface of microporous biochar, and Fourier-transform infrared spectroscopy indicated effective surface functionalization. In addition, although magnetization usually reduces the porosity of carbonaceous adsorbents, the ultraviolet–visible spectroscopic analysis showed that double layer magnetic biochar composite exhibited a much greater ability to remove Ni(II) and Pb(II), with 139 % and 38 % higher adsorptions than raw biochar. Almost complete removal of Pb (91 %) was observed by magnetic-BC and the adsorbent could easily be separated using a neodymium magnet. This high performance can be attributed to the synergistic effect of ultrasound activation on increasing the porosity and surface area of biochar along with enhanced chelation imparted by amine functionalization. The developed technique can be used for synthesizing advanced adsorbents for removal of nuclear waste-related metal ions from aqueous environments.

磁化促进了吸附剂的分离和再利用，但是大大降低了吸附能力。在这项研究中，双层混合磁化/功能化生物炭复合材料是通过热解后的混合磁化作用合成的，这种复合化能持续甚至显着提高微孔碳质生物炭（BC）的吸附能力。开发的过程包括：i）超声波下生物炭的结构改性； ii）磁铁矿（Fe ₃ O ₄磁化））纳米颗粒，和iii）用3-氨丙基三乙氧基硅烷（TES）进行官能化。超声波辐照会剥落并分解生物炭的不规则石墨层，并形成新的或打开的封闭微孔，从而增强BC的孔隙率。就其本身而言，TES稳定了生物炭表面上的磁性纳米颗粒，同时它通过其氨基对金属离子的强螯合能力参与水净化。扫描电镜观察表明Fe ₃ O ₄分布稳定均匀微孔生物炭表面上的纳米颗粒和傅立叶变换红外光谱表明有效的表面功能化。此外，尽管磁化通常会降低碳质吸附剂的孔隙率，但是紫外可见光谱分析表明，双层磁性生物炭复合材料具有更高的去除Ni（II）和Pb（II）的能力，分别高出139％和38％吸附比原始生物炭。磁性BC观察到几乎完全去除了Pb（91％），并且使用钕磁铁可以轻松分离吸附剂。这种高性能可归因于超声活化对增加生物炭的孔隙率和表面积以及胺官能化赋予的增强螯合作用的协同作用。