Key Laboratory of Environmental Nanotechnology and Health Effects, Department of Environmental Nano-materials, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Center of Integrated Water-Energy-Food studies (iWEF), School of Animal, Rural, and Environmental Sciences, Nottingham Trent University, Brackenhurst Campus, NG25 0QF, UK.
J Environ Sci (China). 2019 Jun;80:93-98. doi: 10.1016/j.jes.2018.10.007. Epub 2018 Oct 30.
The traditional degradation of organic pollutants is based on the sacrifice of chemical or biological reagents. In this study, a purely physical technique was developed to break the chemical bonds and consequently decompose macromolecules in aqueous solution. Assisted with a high-speed mechanical blade, refined quartz sand grains with particularly sharp nano-scale edges can act as 'nano-knives', which are able to cut the long chain of carboxymethyl cellulose (CMC, as a model molecule). High performance size exclusion chromatography measurements evidenced that the original CMC molecules (41,000 Da) were decomposed into a series of smaller molecules (460, 1000, 2200, 21,000, 27,000 and 31,000 Da). Consequently, the initial viscosity of the CMC solution (2 g/L) rapidly decreased by approximately 50% after 3 min treatment by the nano-knife materials along with the mechanical blade. Fourier transform infrared (FTIR) spectra indicated that the original functional groups were still present and new functional groups were not produced after shearing. The intensity of the main functional group β-1-4-glycosidic bond (wavenumber 1062 cm) was observed to markedly decrease after shearing. These results indicated that the long-chain CMC was cleaved into short-chain CMC. A degradation mechanism was proposed whereby the cutting force generated by the rapid motion of the nano-knives may be responsible for the breakage of β-1-4-glycosidic bonds in the macromolecular cellulose backbone. These results provide support for a potentially more affordable and environment-friendly strategy for physical-based decomposition of recalcitrant organic pollutants from aqueous solution without the need of chemical or biological reagents.
传统的有机污染物降解方法依赖于化学或生物试剂的消耗。在这项研究中，我们开发了一种纯物理技术，用于打破化学键并使水溶液中的大分子分解。在高速机械刀片的辅助下，具有特别锋利纳米级边缘的精制石英砂粒可以充当“纳米刀”，能够切割羧甲基纤维素（CMC，作为模型分子）的长链。高性能尺寸排阻色谱测量证明，原始的 CMC 分子（41,000 Da）被分解成一系列较小的分子（460、1000、2200、21,000、27,000 和 31,000 Da）。因此，在纳米刀材料和机械刀片的共同作用下，经过 3 分钟处理后，初始 CMC 溶液（2 g/L）的初始粘度迅速降低了约 50%。傅里叶变换红外（FTIR）光谱表明，在剪切后，原始的功能基团仍然存在，并且没有产生新的功能基团。剪切后，主要功能基团β-1-4-糖苷键（波数 1062 cm）的强度明显降低。这些结果表明长链 CMC 被切割成短链 CMC。提出了一种降解机制，即纳米刀快速运动产生的切割力可能负责断裂大分子纤维素骨架中的β-1-4-糖苷键。这些结果为物理降解水溶液中难降解有机污染物提供了支持，不需要化学或生物试剂，是一种更经济、更环保的策略。
