Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763, Republic of Korea.
Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-Ro, Seoul 04763, Republic of Korea; Analysis and Evaluation Department, Egyptian Petroleum Research Institute (EPRI), Nasr City, Cairo 11727, Egypt.
Sci Total Environ. 2020 Nov 15;743:140761. doi: 10.1016/j.scitotenv.2020.140761. Epub 2020 Jul 6.
In an effort to develop a cost-effective mitigation tool for volatile organic compounds, particularly formaldehyde (FA), microporous activated carbon (AC) was modified into three different forms of AC-1, AC-2, and AC-3 using a raw commercial AC product (AC-0). First, AC-1 and AC-2 were produced by the modification of AC-0 with N/S heteroatoms using identical mixture of dicyandiamide and thiourea precursors through either solvothermal (AC-1) or microwave-assisted calcination (AC-2) synthesis. Second, aminosilane-functionalized AC (AC-3) was prepared solvothermally using N-[3-(Trimethoxysilyl)propyl]ethylenediamine reagent. The relative adsorption performances for gaseous FA (1 ppm) in terms of 10% breakthrough volume (BTV10: L atm g) at near-ambient conditions (25 °C and 1 atm) were AC-3 (132) > AC-2 (66.5) > AC-1 (14.2) > AC-0 (10.4). In a comparison based on partition coefficients (mole kg Pa) at BTV10, AC-3 outperformed AC-0 by a factor of 214, while the adsorption performance of AC-2 was 36-times higher than AC-1. The enhanced performance of AC-2 over AC-1 reflected the effect of the microwave synthesis protocol on the improvement of surface chemistry (e.g., N/S doping) and texture (e.g., surface area and pore volume) of AC-based adsorbents as compared to conventional solvothermal method. Further, the prominent role of surface chemistry (e.g., relative to textural properties), as observed with the increases in the amount of doped functional elements (including N:C and silicon:C ratios), is supported by the apparent dependence of performance on the selected modification procedures. Based on kinetic and X-ray photoelectron spectroscopy analyses, the superiority of aminosilylated AC-3 can be attributed to a synergistic effect between physisorption (e.g., pore diffusion) and chemical interactions of the FA carbonyl (C=O) group with amine and silica functionalities (via Mannich coupling [Schiff base] and cycloaddition reaction mechanisms, respectively). This confirms the significance of surface chemistry, relative to pore diffusion, in achieving maximum adsorption of gaseous FA molecules.
为了开发一种针对挥发性有机化合物（尤其是甲醛（FA））的具有成本效益的缓解工具，使用一种原始商业 AC 产品（AC-0）将微孔活性炭（AC）改性为三种不同形式的 AC-1、AC-2 和 AC-3。首先，通过使用相同的双氰胺和硫脲前体混合物，通过溶剂热（AC-1）或微波辅助煅烧（AC-2）合成，用 N/S 杂原子对 AC-0 进行改性，制得 AC-1 和 AC-2。其次，通过 N-[3-(三甲氧基硅基)丙基]乙二胺试剂在溶剂热条件下制备氨基硅烷功能化的 AC（AC-3）。在环境条件（25°C 和 1 atm）下，对于气态 FA（1 ppm）的 10%穿透体积（BTV10：L atm g）的相对吸附性能，AC-3（132）>AC-2（66.5）>AC-1（14.2）>AC-0（10.4）。在基于 BTV10 时的分配系数（摩尔 kg Pa）的比较中，AC-3 的表现优于 AC-0，倍数为 214，而 AC-2 的吸附性能比 AC-1 高 36 倍。AC-2 相对于 AC-1 的增强性能反映了微波合成方案对基于 AC 的吸附剂表面化学（例如，N/S 掺杂）和结构（例如，表面积和孔体积）的改进效果，与传统溶剂热方法相比。此外，观察到掺杂官能团（包括 N:C 和硅:C 比）的数量增加会导致性能提高，这表明表面化学（相对于结构特性）的突出作用得到了支持，这与所选改性程序的性能明显依赖有关。基于动力学和 X 射线光电子能谱分析，氨基硅烷化的 AC-3 的优势可归因于 FA 羰基（C=O）基团与胺和硅官能团之间的物理吸附（例如，孔扩散）和化学相互作用的协同效应（分别通过曼尼希缩合[席夫碱]和环加成反应机制）。这证实了表面化学相对于孔扩散在实现气态 FA 分子最大吸附中的重要性。
