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活性碳纤维不仅对有机物有高的吸附容量,对贵金属离子也具有强的还原吸附能力,可将Pd(II), Ag(I), Au(III)等离子还原为金属单质。因而可用于提取矿液或回收废液中的贵金属。由此,提高或改善贵金属在活性碳纤维上的还原吸附容量或分布形态,显得非常重要。本文研究了活性碳纤维制备条件、表面氧化改性、以及负载有机物等对活性碳纤维还原能力的影响。结果表明,(1)制备条件对剑麻基活性碳纤维的还原能力有很大的影响。用H3PO4或ZnCl2活化的活性碳纤维对银离子具有更高的还原吸附容量,分别可达250和700mg/g,约为水蒸汽活化剑麻基活性碳纤维对银离子还原吸附容量的2倍和5倍。(2)过氧化氢、高锰酸钾、或硝酸等无机氧化剂对活性碳纤维进行表面改性,也能提高活性碳纤维的还原能力。结果表明,虽然改性活性碳纤维的比表面积和孔体积下降10～20%左右,但其表面含氧量及含氧基团的种类发生了改变。这些改性活性碳纤维对Ag(NH3)2+的还原吸附量大幅度提高,可达550mg/g 以上。推断表面改性在活性碳纤维表面创造了更多有利于碱性条件下发生氧化还原的活性点。(3)在活性碳纤维表面负载适当的有机物如亚甲基蓝、苯胺或对硝基苯酚,也能显著提高活性碳纤维对Ag(NH3)2+的还原吸附能力。
Activated carbon fiber not only has high adsorption capacity for organic matter, but also has strong reduction and adsorption capacity for noble metal ions. Pd (II), Ag (I) and Au (III) ions can be reduced to metal elements. It can be used to extract mineral liquid or to recover the precious metal in waste liquid. Therefore, it is very important to improve or improve the reducing adsorption capacity or distribution of precious metals on activated carbon fibers. In this paper, the preparation conditions of activated carbon fiber, surface oxidation modification, as well as the load of organic matter on the reduction of activated carbon fiber. The results showed that (1) the preparation conditions had a great influence on the reducing ability of sisal based activated carbon fibers. Activated carbon fibers activated with H3PO4 or ZnCl2 have higher reductive adsorption capacities for silver ions of up to 250 and 700 mg / g, respectively, which are about two and five times that of water vapor-activated sisal-based activated carbon fibers for silver ion reduction and adsorption capacity . (2) Hydrogen peroxide, potassium permanganate, or nitric acid and other inorganic oxidants on the surface of activated carbon fiber modified, but also can improve the reduction ability of activated carbon fiber. The results showed that although the specific surface area and pore volume of the modified activated carbon fibers decreased by 10 ~ 20%, the surface oxygen content and the types of oxygen-containing groups changed. The reduction of Ag (NH3) 2+ by these modified activated carbon fibers is greatly enhanced, reaching up to 550mg / g. It is inferred that surface modification creates more active sites on activated carbon fibers that favor redox reactions under alkaline conditions. (3) Adsorption of activated carbon fibers on Ag (NH3) 2+ can also be significantly improved by loading appropriate organic compounds such as methylene blue, aniline or p-nitrophenol on the surface of activated carbon fibers.