ABSTRACT
Alumina nanofibers were prepared by a technique that combined the sol-gel and electrospinning methods. The solution to be electrospun was prepared by mixing aluminum isopropoxide (AIP) in ethanol, which was then refluxed in the presence of an acid catalyst and polyvinylpyrolidone (PVP) in ethanol. The characterization results showed that alumina nanofibers with diameters in the range of 102 to 378 nm were successfully prepared. On the basis of the results of the XRD and FT-IR, the alumina nanofibers calcined at 1,100°C were identified as comprising the α-alumina phase, and a series of phase transitions such as boehmite â γ-alumina â α-alumina were observed from 500°C to 1,200°C. The pore size of the obtained γ-alumina nanofibers is approximately 8 nm, and it means that they are mesoporous materials. The kinetic study demonstrated that MO adsorption on alumina nanofibers can be seen that the pseudo-second-order kinetic model fits better than the pseudo-first-order kinetic model.
ABSTRACT
Dichloromethane is one of the chlorinated volatile organic compounds (CVOCs) that contaminate the waters. Especially, the dichloromethane used as a solvent in polycarbonate synthesis, is dissolved in wastewater with the saturated solubility of 17,220 mg L(-1), which is several times that of other CVOCs. Thus, it is reasonable to recover the dichloromethane dissolved in water instead of destruction based on the economic point of view. To study on the recovery of the dichloromethane, adsorption equilibrium and column dynamics were investigated using a hydrophobic polymer resin (XAD-1600) without the ion-exchange functional groups. In addition, a hydrophilic polymer resin (XAD-7) and an activated carbon (DY-GAC) were chosen for comparison. Conventional two- or three-parameter models such as the Langmuir, Freundlich, or Sis equations could not fit the adsorption equilibrium data of two polymer resins obtained over the entire range of concentration (1-200 mol m(-3)). They were well fitted by a hybrid model consisting of Langmuir and BET (Brunauer-Emmett-Teller) equations. The adsorption amount at high concentration was in the order of XAD-1600>XAD-7>DY-GAC on a mass basis. To confirm the possibility of using resin as a sorbent for the removal of dichloromethane, adsorption breakthrough curves were measured under key operating conditions such as the concentration, the flow rate, and the column length. Moreover, desorption from polymer resins adsorbed with dichloromethane was conducted by using pure water only as a desorbate. A simple dynamic model was also formulated to describe the adsorption breakthrough curves of dichloromethane from XAD-1600, XAD-7 and DY-GAC columns.
