Here, a novel nitrogen-doped carbon nano-material (N-CGNM) with hierarchically porous structure was prepared from spent coffee ground for efficient adsorption of organic dyes by a simple one-step carbonization process (the uniform mixture consists of spent coffee ground, urea, and CaCl₂ with the ratio of 1:1:1, which was heated to 1000 °C with a rate of 10 °C min⁻¹ and held at 1000 °C for 90 min in N₂ atmosphere to carry out carbonization, activation, and N-doping concurrently). The morphology and structure analysis show that the prepared N-CGNM exhibits hierarchical pore structure, high specific surface area (544 m²/g), and large numbers of positively charged nitrogen-containing groups. This unique structure and chemical composition endow N-CGNM with an excellent adsorption capacity toward anion Congo red (623.12 ± 21.69 mg/g), which is obviously superior to that (216.47 ± 18.43 mg/g) of untreated spent coffee ground-based carbon nano-materials (CGM). Oppositely, the adsorption capacity of N-CGNM towards cation methylene blue is inferior to that of CGM due to the existence of electrostatic repulsion. These findings show a great guidance for the development of low-cost but efficient selective adsorbent.

在这里，由废咖啡渣制备了一种具有分层多孔结构的新型氮掺杂碳纳米材料（N-CGNM），可通过一个简单的一步碳化过程就有效地吸附有机染料（均匀的混合物由废咖啡渣组成，尿素和CaCl ₂以1：1：1的比例，以10°C min ^-1的速率加热到1000°C，并在N ₂气氛中于1000°C保持90分钟以进行碳化，激活和同时进行N掺杂）。形态和结构分析表明，所制备的N-CGNM具有分层的孔结构，比表面积高（544 m ^2）。/ g），以及大量带正电的含氮基团。这种独特的结构和化学组成使N-CGNM对刚果红具有极好的吸附能力（623.12±21.69 mg / g），明显优于未经处理的磨碎咖啡渣基碳（216.47±18.43 mg / g）。纳米材料（CGM）。相反，由于存在静电排斥，因此N-CGNM对阳离子亚甲基蓝的吸附能力不如CGM。这些发现为开发低成本但有效的选择性吸附剂提供了很好的指导。