This study enlightened a green and novel method to prepare magnetic bio-derived chars by physical co-mixing and the Pb²⁺ adsorption behavior of these chars was investigated. Three kinds of magnetic chars were fabricated by wheat stalk biochar, rice husk biochar, and commercial coconut husk activated carbon co-mixing with magnetic nano-iron tetroxide (Fe₃O₄), respectively. The microstructure, magnetism properties, adsorption performance, and mechanism of magnetic chars were systematically investigated with multiple approaches. The experimental results showed that optimized Fe₃O₄ magnetic chars with the mass ratio of 1:3 (chars to Fe₃O₄) exhibited excellent Pb²⁺ adsorption ability and magnetic separation characteristics. The adsorption kinetics was well described by the pseudo-second order model indicating that the Pb²⁺ adsorption rate and amount of magnetic chars were enhanced. The maximum Pb²⁺ adsorption capacities of magnetic wheat stalk biochar, wheat stalk biochar, magnetic rice husk biochar, rice husk biochar, magnetic coconut husk activated carbon, and coconut husk activated carbon were 179.85, 160.39, 95.44, 73.34, 43.38, and 39.15 mg/g, respectively. Furthermore, the mechanism analysis indicated that the Pb²⁺ adsorption on Fe₃O₄ magnetic bio-derived chars included the co-precipitation reaction, complexation reaction, conjugation adsorption, ion exchange, and Fe–O coordination. This study presents an attractive method for preparing magnetic bio-derived chars for enhancing heavy metal adsorption without chemical processes and mechanical energy.

这项研究启发了一种绿色和新颖的方法，通过物理共混制备生物磁性磁性炭，并研究了这些炭的Pb ²⁺吸附行为。分别通过小麦秸秆生物炭，稻壳生物炭和商业椰子壳活性炭与磁性四氧化_三铁（Fe ₃ O ₄）共混制备了三种磁性炭。用多种方法系统地研究了炭的微观结构，磁性，吸附性能和机理。实验结果表明，优化的Fe ₃ O ₄磁性炭的质量比为1：3（炭与Fe ₃ O ₄）具有极好的Pb ²⁺吸附能力和磁分离特性。拟二级模型很好地描述了吸附动力学，表明Pb ²⁺吸附速率和磁性炭量得到了提高。磁性小麦秸秆生物炭，小麦秸秆生物炭，磁性稻壳生物炭，稻壳生物炭，磁性椰子壳活性炭和椰子壳活性炭的最大Pb ²⁺吸附能力分别为179.85、160.39、95.44、73.34、43.38和39.15。分别为mg / g。此外，机理分析表明Pb ²⁺在Fe ₃ O ₄上的吸附磁性生物焦炭包括共沉淀反应，络合反应，共轭吸附，离子交换和Fe-O配位。这项研究提出了一种有吸引力的方法，用于制备磁性生物焦炭，以增强重金属的吸附，而无需化学过程和机械能。