In this study, preparation of hierarchically porous biochar (PB) and simultaneous nutrient recovery from sewage sludge were realized through three steps of KHCO₃-activated pyrolysis, water leaching and acid leaching. The prepared PB samples were applied as adsorbents for the removal of 4-chlorophenol (4-CP) from aqueous solutions. Effect of pyrolysis temperature on the physicochemical properties of PB samples was investigated. The PB prepared at 900 °C (PB-900) had the highest surface area (1476.0 m²/g) and total pore volume (1.138 cm³/g). The formation mechanism of porous structure of PB-900 was revealed by investigating the phase transformation, element distribution and pore structure evolution during its whole preparation process. PB-900 showed a high 4-CP adsorption rate of 14.4 mg/(g∙min), and its maximum adsorption capacity for 4-CP was up to 192.4 mg/g. The mechanism of 4-CP removal by PB-900 was mainly physical adsorption, and its strong aromaticity strengthened its interaction with 4-CP through π-π bonding. The water leaching solution in the preparation process of PB-900 contained a lot of nutrient elements (K, Si, P), which was recovered for grass seeds germination. Compared with the samples cultured with ultrapure water only, the seed germination rate of samples cultured with ultrapure water added with 20% of pretreated water leaching solution increased from 63% to 80%, and the average shoot length of grass grown for 7 days increased by 51.4%. The findings of this study suggest that KHCO₃ is an alternative activator to prepare hierarchically porous biochar adsorbent from sewage sludge and realize simultaneous nutrient recovery.

本研究通过KHCO ₃活化热解、水浸和酸浸三个步骤实现了分级多孔生物炭（PB）的制备和污泥养分的同步回收。制备的 PB 样品用作吸附剂，用于从水溶液中去除 4-氯苯酚 (4-CP)。研究了热解温度对PB样品理化性质的影响。在 900 °C 制备的 PB (PB-900) 具有最高的表面积 (1476.0 m ² /g) 和总孔体积 (1.138 cm ³/G）。通过研究PB-900整个制备过程中的相变、元素分布和孔结构演变，揭示了PB-900多孔结构的形成机制。PB-900 表现出 14.4 mg/(g∙min) 的高 4-CP 吸附率，其对 4-CP 的最大吸附容量高达 192.4 mg/g。PB-900去除4-CP的机理主要是物理吸附，其强烈的芳香性通过π-π键加强了与4-CP的相互作用。PB-900制备过程中的浸出液中含有大量的营养元素（K、Si、P），可回收用于草种萌发。与仅用超纯水培养的样品相比，用超纯水加20%预处理水浸出液培养的样品种子发芽率从63%提高到80%，生长7天的草平均芽长提高了51.4%。本研究结果表明 KHCO₃是一种替代活化剂，用于从污水污泥中制备分级多孔生物炭吸附剂并实现同步养分回收。