Nitrogen recovery from bio-based digestate has attracted considerable interests recently, but has been limited by the indirect capture of organic or insoluble nitrogen and the lower sorption ability of hydrochar. To mitigate these challenges, we used a hydrothermal pretreatment to promote the conversion of insoluble or organic nitrogen. Activated hydrochar was synthesized by using potassium hydroxide to enhance its sorption capacity, and the hydrochar was characterized by Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface-area analysis, and scanning electron microscopy. An optimal efficiency was achieved at 210 °C, with 93.45% total nitrogen solubilization into ammonium. The sorption data of ammonium on the activated hydrochar fitted the pseudo second order kinetics and Langmuir model well. This reaction was dominated by chemisorption, which referring to the formation of bonds between (oxygen-containing) functional groups and ammonium. The maximum ammonium adsorption on the activated hydrochar at 260 °C (260AH) was 108.57 mg g⁻¹. The ammonium sorption was endothermic, spontaneous and associated with a disorder increase on the solid-liquid interface. Once saturated, the ammonium was released continually from activated hydrochar and is anticipated to show an optimal performance in an alkaline environment. The amount of ammonium that was released from the saturated activated hydrochar at 260 °C after five extractions was 13.09 mg g⁻¹. The nitrogen mass-balance calculations show that 10.14% total nitrogen was recovered after nitrogen solubilization, capture, and release. Therefore, potassium-hydroxide-activated hydrochar performed as a promising composite sorbent for ammonium.

从生物基消化物中回收氮的兴趣近来备受关注，但受到有机或不溶氮的间接捕获以及水焦炭吸附能力降低的限制。为了缓解这些挑战，我们使用了水热预处理来促进不溶性或有机氮的转化。利用氢氧化钾增强吸附剂的吸附能力，合成了活性炭，并通过傅里叶变换红外光谱，Brunauer-Emmett-Teller表面积分析和扫描电子显微镜对活性炭进行了表征。在210°C时达到了最佳效率，总氮溶解在铵中的比例为93.45％。铵盐在活性炭上的吸附数据很好地拟合了拟二级动力学和Langmuir模型。该反应以化学吸附为主，化学吸附指的是在（含氧的）官能团和铵之间形成键。在260°C（260AH）下，活化水炭的最大铵吸附量为108.57 mg g^-1。铵的吸收是吸热的，自发的并且与固-液界面上的无序增加有关。铵一旦饱和，就会从活化的碳氢化合物中连续释放出来，并有望在碱性环境中表现出最佳性能。五次萃取后，在260°C下从饱和活性炭中释放出的铵量为13.09 mg g ^-1。氮的质量平衡计算表明，氮溶解，捕获和释放后，总氮的回收率为10.14％。因此，氢氧化钾活化的碳氢化合物作为铵的有前途的复合吸附剂发挥了作用。