以玉米秸秆为原料，采用磷酸(H₃PO₄)活化改性、氢氧化钾(KOH)负载K⁺改性并炭化的方式制备改性玉米秸秆生物炭(以下简称生物炭)。利用SEM、BET、XRD、ICP、XPS以及FT-IR等表征手段，对生物炭的结构进行表征。以制备的生物炭为吸附剂，测定其对模拟废水中亚甲基蓝(MB)的吸附性能。结果表明，K⁺改性后生物炭为柱状片层结构并生成更丰富孔隙，表面含有－OH、－COOH等含氧官能团，且K⁺改性后含氧官能团呈现专一化发展趋势。生物炭对MB具有良好的吸附作用，中性与碱性环境下吸附效果较好，最大吸附容量为222.93 mg/g，较未改性生物炭(68.38 mg/g)和磷酸(H₃PO₄)活化改性生物炭(180.49 mg/g)分别提升226.02%和23.51%。K⁺改性生物炭对MB吸附的动力学和等温线模型分别符合拟二级动力学模型和Langmuir模型，吸附过程为单分子层吸附，且受物理吸附与化学吸附共同作用，其中化学吸附在吸附过程中占主导地位。针对吸附中的扩散过程进行了液膜扩散模型模拟和颗粒内扩散模型模拟，液膜扩散模型曲线斜率为0.6，因此液膜扩散不是扩散过程的主控步骤，颗粒内扩散过程分为膜扩散阶段(0～25 min)和颗粒内扩散阶段(25～140 min)，颗粒内扩散阶段较膜扩散阶段吸附速率明显降低(k_id2=6.453 5<k_id1=32.266 9)，且此模型拟合曲线不通过原点，颗粒内扩散阶段是控速关键阶段。通过热力学分析，得到K⁺改性生物炭对MB的吸附热力学参数，其中分离系数R_L均在0～1，ΔH=7.611 2 kJ/mol>0，ΔG均为负值，表明MB在生物炭上的吸附是可逆且自发吸热的，升温有助于吸附进行；ΔS=30.041 5 J/(mol·K)>0，表明吸附过程中固液界面随机性增加。

Using corn stalks as raw materials, modified corn stalk biochar (hereafter referred to as biochar) was prepared by phosphoric acid (H₃PO₄) activation modification, potassium hydroxide (KOH) loading K⁺ modification and carbonization. The structure of the biochar was characterized using SEM, BET, XRD, ICP, XPS, and FT-IR. The prepared biochar was used as adsorbent to determine its adsorption performance on methylene blue (MB) in the simulated wastewater. The results showed that the K⁺-modified biochar had a columnar lamellar structure with richer pores and contained the oxygen-containing functional groups such as —OH and —COOH on the surface, and the oxygen-containing functional groups showed a trend of specialization after K⁺ modification. The maximum adsorption capacity was 222.93 mg/g, which was 226.02% and 23.51% higher than that of unmodified biochar (68.38 mg/g) and the phosphoric acid (H₃PO₄)-activated modified biochar (180.49 mg/g), respectively. The kinetic and isotherm models were consistent with the proposed secondary kinetic model and the Langmuir model, respectively, and the adsorption process was unimolecular layer adsorption and was subject to both physical and chemical adsorption, with chemical adsorption dominating in the adsorption process. The liquid film diffusion model simulation and the intraparticle diffusion model simulation were carried out for the diffusion process in adsorption. The slope of the liquid film diffusion model curve was 0.6, so the liquid film diffusion was not the main control step of the diffusion process, and the intraparticle diffusion process was divided into the membrane diffusion stage (0−25 min) and the intraparticle diffusion stage (25−140 min). The intraparticle diffusion stage is significantly lower than the membrane diffusion stage in terms of adsorption rate (k_id2=6.453 5<k_id1=32.266 9), and this model fitting curve does not pass through the origin, and the intraparticle diffusion stage is the key stage for rate control. The thermodynamic parameters of the adsorption of MB on the K⁺-modified biochar were obtained by thermodynamic analysis, in which the separation coefficients RL were all between 0 and 1, ΔH=7.611 2 kJ/mol>0, and ΔG were all negative, indicating that the adsorption of MB on the biochar is reversible and spontaneous heat absorption, and the warming helps the adsorption to proceed. ΔS=30.041 5 J/(mol·K)>0, indicating the increase of randomness at the solid-liquid interface during the adsorption process.