Adsorption Characteristics of Iron-Cyanide complex on r-Al2O3

• Main Authors: Cheng, Wen-Po, 鄭文伯
• Other Authors: Huang Chihpin
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/13875129115654861655

博士 === 國立交通大學 === 土木工程學系 === 85 === ABSTRACT Cyanide compound is commonly found as a waste water contaminant on s everal industrial processes such as electroplate, mining, photographic, metall urgical, synthetic fiber and industrial gas purification and so on. Although c yanide compound exists in small amount in the nature system, it is tightly con trolled and highly toxic chemical material. "Industrial cyanide salt" includes simple free cyanide and metal complex cyanide, the former exists in the form of CN- and HCN. Free cyanide is highly toxic, the le This proposed research p roject aims at the study of adsorption behavior of ferricyanide and ferrocyani de on the aluminum oxide (g-Al2O3) surface as a functions of pH and concentrat ion with batch experiments. Attempts to describe and predict the adsorption of ferrocyanide/ferricyanide by aluminum oxide particle will be treated surface sites as homogeneous groups with intrinsic constant using a triple-layer mode l or with a single adsorption constant incorporating proton competition effect using a modified The experiment results indicated, the adsorption percentag es of ferricyanide and ferrocyanide on g-aluminum oxide decreased with increas ing pH and initial concentration of ferricyanide and ferrocyanide. The triple- layer model was used for simulating ferricyanide and ferrocyanide adsorption o n g-aluminum oxide surface. Then, AlOH2+--Fe(CN)63- and AlOH2+--HFe(CN)63- hav e been shown with outer-sphere reaction products to be more agreeable with exp erimental adsorption observation than complexation with other The modified L angmuir isotherm model developed herein can accurately predict the apparent eq uilibrium constant at different pH values and temperature for ferrocyanide and ferricyanide adsorption onto aluminum oxide surface. In the experimental pH r ange of 5~7.5, adsorption capacity and apparent constants decrease as the temp erature increases. According to the Gibbs-Helmholtz equation, these apparent c onstants at various temperature and pH conditions can be applied to determine enthalpy changes (DHo) for t By batch experiments, under the condition of pH 6.0, 25℃, electrolyte concentration 0.01M, the maximum adsorption capacity of kaolinite, aluminum oxide and hydrous iron oxide are 3.1*10-8、4.2*10-7、5.0* 10-7 mol/m2 for ferricyanide and 5.8*10-8、6.3*10-7、1.1*10-6 mol/m2 for ferro cyanide adsorption。This results shown a strong relationship between the value s of adsorption capacity and the site density of oxide surface. From there highly valence, the ferrocyanide and ferricyanide ion have strong coagulation ability in natural water system. In our study, a series of batch test with al uminum oxide turbid water were performed to evaluate the coagulation effective ness of anion with different valence. There are dramatic difference in the coa gulation abilities of simple ions (Cl-、SO42-、Fe(CN)63-、Fe(CN)64-), and othe r species that interact chemically with the oxide surface (H2PO4-). The eviden ces infer that the mechanism of