SBIR Phase I: Removal of Toxic Microcystins in Water Using Graphite Nanofibers

这个小型企业创新研究（SBIR）一期项目涉及使用石墨纳米纤维（GNF）作为去除水中生物毒素的新型吸附介质。具体来说，研究将侧重于去除微囊藻毒素lr，这是一种可能被恐怖分子用来攻击人类的潜在生物武器。人们提出了多种方法来去除水中的微囊藻毒素，包括活性炭吸附、氯化、臭氧氧化、高锰酸盐、过氧化氢、光解和半导体光催化。在这些方法中，活性炭处理似乎是最有效的程序之一。各种微囊藻毒素可以吸附在活性炭的多孔表面，去除效率取决于孔隙大小和表面功能。在吸附过程中起主导作用的是中孔（2 ~ 50nm）的体积，而不是微孔（2 nm）或大孔（50nm）的体积。此外，随着时间的推移，由于生物膜在活性炭表面的积累，去除效率逐渐降低。废活性炭的再生不是一项简单的任务，因此被污染的材料经常被丢弃。使用过的活性炭处理不当可能会引起严重的问题，因为众所周知，微囊藻毒素在室温干燥条件下储存可持续多年，并能在水中煮沸数小时。由于GNF含有丰富的边缘位点，表面功能可以很容易地转换为疏水性或亲水性。此外，最近发现，经过适当的热处理，可以产生具有大部分平均尺寸为12纳米的介孔的GNF结构。这种不寻常的混合性质使GNF从水中吸附微囊藻毒素的理想候选者。此外，GNF表现出的高度结晶完美性使人们能够在氧化气体存在的情况下将材料加热到超过500℃的温度，从而允许去除被捕获的微囊藻毒素和吸附质的再生。

This Small Business Innovation Research (SBIR) Phase I project deals with the use of graphite nanofibers (GNF) as novel adsorption media for the removal of bio-toxins from water. Specifically, the research will focus on the removal of microcystin-LR, a potential biological weapon that could be used by terrorists to attack human beings. Various methods have been proposed for the removal of microcystins from aqueous media, including adsorption by activated carbon, chlorination, ozonation, permanganate, hydrogen peroxide, photolysis, and semiconductor photo-catalysis. Of these approaches, the activated carbon treatment appears to be one of the most effective procedures. Various microcystins can be adsorbed on the porous surface of activated carbon and the efficiency of removal depends upon the pore size and surface functionality. It is claimed that the dominant factor in the adsorption process is the volume of mesopores (2-50 nm diameter) rather than the volume of micropores (diameter 2 nm) or megapores (diameter 50nm). In addition, the removal efficiency gradually decreases over a period of time due to the accumulation of a bio-film on the activated carbon surface. The regeneration of the spent activated carbon is not a simple task and as consequently the contaminated material is frequently discarded. Improper disposal procedures of used activated carbons could give rise to serious problems because microcystins are known to persist for many years when stored in dry conditions at room temperature and to withstand many hours of boiling in water. Since GNF contain an abundance of edge sites, the surface functionality can easily be transformed to give either hydrophobic to hydrophilic properties. In addition, it has recently been discovered that following suitable thermal treatments it is possible to generate GNF structures that possess a large fraction of mesopores having average dimensions of 12 nm. This unusual blend of properties makes GNF ideal candidates for the adsorption of microcystins from water. Furthermore, the high degree of crystalline perfection exhibited by GNF enables one to heat the materials in the presence of oxidizing gases to temperatures in excess of 500 C, thereby allowing for the removal of trapped microcystins and the regeneration of the adsorbate.