Chemical Activation of Diatomaceous Earth by Hydrofluoric Acid

• Main Authors: Chih-Wei Lai, 賴智濰
• Other Authors: Wen-Tien Tsai
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/48527296015492466536

碩士 === 嘉南藥理科技大學 === 環境工程與科學系暨研究所 === 92 === The objective of this study was to use hydrofluoric acid (HF) as etching agent for chemically activating fresh and spent diatomaceous earths under different activation parameters including impregnation concentration, holding time, temperature etc. The experimental results showed that the optimal activation conditions for fresh diatomaceous earth seemed to be at the concentration of HF 2.5 N, holding time of 0.5 hr, temperature of 60 ℃ and sample/solution weight ratio of 5/100. Under these conditions, the main physical properties of resulting product were BET surface area of 7.04 m2/g and total pore volume of 0.0560 cm3/g as compared to 3.81 m2/g and 0.0161 cm3/g of its precursor, respectively. Compared to the foregoing, the optimal activation conditions for spent diatomaceous earth seemed to be similar to those of fresh diatomaceous earth except temperature at 25 ℃. Under these conditions, the main physical properties of resulting product were BET surface area of 4.85 m2/g and total pore volume of 0.0430 cm3/g as compared to 0.43 m2/g and 0.0036 cm3/g of its precursor, respectively. The physical and chemical properties characterizations of some resulting products obtained in the chemical activation were further examined using the analyses of surface area/pore volume, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR) and main elements. The analytical results showed that these samples are basically characteristic of types II and IV base on the nitrogen isotherm, indicating mesoporous-macroporous structure. Finally, the optimal porous product was used as a mineral adsorbent for environmental hormone bisphenol-A, showing that it has a poor adsorption capacity for the removal of this hydrophobic organic compound from the aqueous solution based on the fittings of Langmuir and Freundlich isotherms, mainly due to the electrostatic repulsion interaction between the adsorbent with negatively-charged surface and adsorbate with neutrally-polar structure.