Applications of supercritical fluid( SCF) have received widespread attention over the past years. One of these applications is to regenerate adsorbents, such as activated carbons and polymeric adsorbents. Many studies show that the supercritical regeneration technology is economical even though the regenerating temperature and pressure are above 387K and15MPa(150atm) respectively, and presents many advantages over traditional regeneration methods.There is little loss of surface area in a process of supercritical regeneration, compared to thermal regeneration where harsh temperature and attrition result in a capacity reduction of adsorbents. Supercritical fluids have enhanced mass-transfer properties over common solvent, and can be conveniently removed from the adsorbate that is a major concern in solvent regeneration.The fragmentation of the adsorbents that usually occurs in ultrasonic regeneration is not a problem in supercritical regeneration[1]. The first study of supercritical regeneration appears to be the research of DeFilippi et al. and Modell et al. who studied the regeneration of activated carbon loaded with pesticides and presented the information on process development. Tan and Liou provided published information in detail for evaluating rate models. Kikic et al. measured the adsorption isotherms of a system of "SCF CO2-salicylicacid-activated carbon" by monitoring the salicylic acid concentration with an on-line UV detector. The supercritical chromatography technology was propose by Cross et al. to estimate the adsorption isotherms under supercritical condition. Phenol is a kind of toxic organic pollutant commonly emitted from industrial effluents. Activated carbons and polymeric adsorbents are customarily employed as solid matrix to remove phenol from the environmental concern because they have large specific surface area, high and stable adsorption capacity, high adsorption efficiency, etc. However, because of the high affinity of adsorbents for phenol and the irreversible adsorption of phenol on adsorbents, the regeneration of activated carbons and polymeric adsorbents is still a problem. Phenol is soluble in SCF CO2, so it seems to be a promising method to regenerate activated carbons and polymeric adsorbents loaded with phenol by SCF CO2 according to the above studies. The main objective of this paper is to measure the adsorption isotherms of phenol on activated carbons and polymeric adsorbents under supercritical condition and to investigate the influence of the third component on the adsorption isotherms. Moreover, a new method named as "volume-expanding and pressure-reducing adsorption" is proposed to measure the isotherms under the supercritical condition without the high-pressure UV detector.
超临界流体(SCF)的应用在过去几年中受到了广泛关注,形如活性炭和聚合物吸附剂之类吸附剂的再生就是这些应用中的一种。许多研究表明,超临界再生技术即使在再生温度和压力分别高于387K和15MPa(150atm)时依然具有可行性,并表现出很多相对于传统再生方法的优势。与热量再生过高的温度以及摩擦导致吸附容量减少相比较,超临界再生的过程中表面损失非常微小。超临界流体增强了普通溶剂的传质特性,同时又很容易与作为溶剂再生要素的被吸附物分离。超声波再生中时常发生的吸附剂破碎的问题在超临界再生中也不存在。 超临界再生的初期研究据称出自DeFilippi 等和Modell 等,当时研究了吸附有杀虫剂的活性炭的再生,并披露了工艺过程研发的内容。Tan和Liou为评估速率模型提供了详细的正式出版信息。Kikic等通过使用在线紫外检测仪监测水杨酸含量,测定了“SCF CO2-水杨酸-活性炭”系统的吸附等温线。Cross等为测定超临界情况下的吸附等温线,提出了超临界色谱法技术。 苯酚是一种毒性有机污染物,通常源自工业废水。习惯上使用活性炭和聚合物吸附剂作为固相基质,用于环境污染处理中酚类的去除,因为它们特有较大的表面积、较高而稳定的吸附容量、较高的吸附率等等。但是, 由于吸附剂对苯酚的高度亲合力,加之苯酚在吸附剂上属于不可逆吸附, 活性炭和聚合物吸附剂的再生仍然是一个问题。苯酚在二氧化碳超临界流体(SCF)里可溶解,按照上述理论,使用二氧化碳SCF来再生已加载苯酚的活性炭和聚合物吸附<
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