The ability of biochars, derived from the pyrolysis at 400 °C; 500 °C and 600 °C of pretreated cypress sawdust with 20 wt% magnesium chloride (MgCl₂) solutions, in recovering phosphorus from aqueous solutions was investigated under various experimental conditions in batch mode. The experimental results indicated that cypress sawdust pretreatment with MgCl₂ induced important modifications of the physical and chemical biochars' properties favoring phosphorus recovery from the used synthetic solutions. Moreover, phosphorus recovery efficiency increased with the increase of the used pyrolysis temperature. Indeed, for an aqueous pH of 5.2 and a phosphorus concentration of 75 mg L⁻¹, the recovered amounts increased from 19.2 mg g⁻¹ to 33.8 mg g⁻¹ when the used pyrolysis temperature was raised from 400 °C to 600 °C. For all the tested biochars, the phosphorus recovery kinetics data were well fitted by the pseudo-second-order model, and the equilibrium state was obtained after 180 min of contact time. Furthermore, the phosphorus recovery data at equilibrium were well described by the Langmuir model with a maximal recovery capacity of 66.7 mg g⁻¹ for the magnesium pretreated biochar at 600 °C. Phosphorus recovery by the used biochars occurred probably through adsorption onto biochars' active sites as well as precipitation with magnesium ions as magnesium phosphates components. All these results suggested that biochars derived from MgCl₂ pretreated cypress sawdust could be considered as promising materials for phosphorus recovery from wastewaters for a possible further subsequent use in agriculture as amendments.

生物炭的能力，源自400°C的热解；在各种实验条件下，以分批方式研究了用20 wt％氯化镁（MgCl ₂）溶液对500℃和600℃的柏木屑进行预处理的方法。实验结果表明，用MgCl ₂预处理柏木锯末会引起物理和化学生物炭性质的重要变化，有利于从使用过的合成溶液中回收磷。此外，磷的回收效率随着使用的热解温度的升高而提高。实际上，对于pH为5.2的水溶液和75 mg L ^-1的磷浓度，回收量从19.2 mg g ^-1增加当所使用的热解温度从400°C升高至600°C时，达到33.8 mg g ^-1。对于所有测试的生物炭，磷的回收动力学数据均通过拟二级模型拟合，并且在接触时间180分钟后获得了平衡状态。此外，Langmuir模型很好地描述了平衡状态下的磷回收数据，在600°C下对镁预处理的生物炭的最大回收能力为66.7 mg g ^-1。用过的生物炭回收磷的过程可能是通过吸附到生物炭的活性位点上以及以镁离子作为磷酸镁成分进行的沉淀来实现的。所有这些结果表明，生物炭源于MgCl ₂ 经预处理的柏木锯末可被视为从废水中回收磷的有前途的材料，有可能在以后的农业中进一步用作修正品。