Adsorption of Environmental Hormones Using Magnetic Adsorbent: A Case Study of Dimethyl Phthalate
Date Issued
2007
Date
2007
Author(s)
Lu, De-Sheng
DOI
zh-TW
Abstract
Dimethyl phthalate (DMP) is a member of environmental hormones. It exists with low concentration and is harmful to biological and cell`s mechanism even with a very low exposed concentration. Adsorption is chosen to remove and concentrate DMP for further oxidizing, degrading or other treating processes.
Fe3O4 (M) is prepared by precipitation method and then synthesized to magnetic polyvinyl acetate (M-PVAC) by suspension polymerization. Its surface is modified by alcoholization to produce a polymer adsorbent of magnetic polyvinyl alcohol (M-PVAL). The saturated magnetizations of particles M, M-PVAC and M-PVAL are 57.2, 26.0 and 43.2 emu g-1 with super-para-magnetism, respectively. The average particle size of M-PVAL by number is 0.75 μm in micro size.
Global kinetic expressions are simulated by pseudo-first-order equation, pseudo-second-order equation and Elovich rate equation in completely stirred tank reactor (CSTR) system. Traditional kinetic models of pore and surface diffusions are also employed. As a result, time to reach equilibrium is faster when the initial concentration of DMP is higher because of the high gradient of concentrations between solid and liquid.
The isotherm experiments include three cases: (1) with no adjustment of initial pH (pH0) of solution, (2) pH0 = 5 and (3) pH0 = 7. The results are simulated by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The saturated amounts of adsorption of unimolecular layer (qL) of Langmuir isotherm are 5.21, 4.21 and 4.22 mg g-1 in these three cases and the values of heterogeneity factor nF of Freundlich isotherm are 2.19, 2.59 and 2.59 which are greater than 1. It reveals the DMP/M-PVAL system is belong to favorable adsorption. The values of adsorption activation energy per mole (EF) of D-R isotherm in these cases are 6.48, 7.04 and 7.19 kJ mol-1which are less than 8 kJ mol-1, indicating that the adsorption process is belong to the form of physical nature.
The values of qL for the adsorption of DMP in three solutions containing 0, 10 and 50 vol.% alcohol are 5.21, 4.03 and 1,18 mg g-1, respectively. It shows the more content of methnol the less the concentration in solid M-PVAL (qL). The values of EF in these three experimental sets are 6.48, 5.89 and 4.68 kJ mol-1 , indicating that stable bond forms between the methanol and DMP so that the affinity between them is better than that between the adsorbent and DMP. Using the characteristics between methanol and DMP to desorption process, the desorption efficiency is as high as 95 % by twice desorption units applying 50 vol.% methnol.
Subjects
環境荷爾蒙
鄰苯二甲酸二甲酯
吸附
磁鐵礦
懸浮聚合
聚乙烯醇
吸附動力
environmental hormones
dimethyl phthalate
magnetite
polyvinyl alcohol
suspended polymerization
adsorption isotherm
adsorption kinetic
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-R94541119-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):e3d1ae78b8b2a8772937b0e0e74edf13