Cheol-Ju Kim

Recovery of anionic surfactant by RO process.: Part I. Preparation of polyelectrolyte-complex anionic membrane

Abstract Crosslinked sodium alginate (SA) membranes which have a protective polyelectrolyte complex layer at a membrane surface were prepared by a simple technique for the reverse osmosis separation of an anionic surfactant that has been used as an emulsifier in PTFE emulsion polymerization. With this technique, when a nascent SA film cast onto a glass plate was dipped in the reaction solution that contained both CaCl 2 , a crosslinking agent, and chitosan, a cationic polymer, the stable SA membrane with double layer structure was fabricated by crosslinking with the divalent ion Ca 2+ inside the membrane and the simultaneous polyelectrolyte complexation of anionic SA with cationic chitosan at the membrane surface. The effects of the fabrication parameters on the characteristics of the resulting membrane were investigated. The complex membrane gave excellent membrane performance with rejections higher than 99% due to electrostatic repulsion between anionic solute molecules and the anionic membrane. Also, a comparison of membrane performance between crosslinked SA membranes with and without the protective complex layer was made at different operating conditions in the reverse osmosis separation of the anionic surfactant from waste fluids. The role of the protective polyelectrolyte complexes formed at the membrane surface is discussed in terms of membrane stability.

Recovery of anionic surfactant by RO process. Part II. Fabrication of thin film composite membranes by interfacial reaction

Abstract A new technique has been established to fabricate thin film composite membranes, by which a hydrophilic polymer could be coated in thin film on a hydrophobic support membrane. The new technique was composed of two steps: dispersion of a reactant to the hydrophilic polymer in the hydrophobic support membrane and interfacial reaction between the reactant and the hydrophilic polymer to produce thin film of the hydrophilic polymer on the support membrane. Composite membranes in which a thin film of sodium alginate is coated on a polysulfone support membrane were prepared by the new technique for the reverse osmosis separation of anionic surfactant–water mixture. Two methods were employed to fabricate a thin film of sodium alginate on the support membrane: (1) dispersion of the crosslinking agent, CaCl 2 alone in the support membrane and (2) dispersion of CaCl 2 in the support membrane with help of PVA which adheres fast to the support membrane. The formation mechanism of the thin layer was suggested schematically on each method. Both the methods could produce successively a thin layer of SA on the support membrane. Especially, method (2) gave a strong bonding of the thin layer on the support because of the large contact area with the support through the PVA layer which sticks fast to the SA layer. From the SEM pictures and permeation experiments, the method (2) was confirmed to be better to produce a defect-free thin film of SA on the support membrane.

Theoretical study of the structures and nonlinear optical properties of hydrogen-bonded nitroaniline systems

Abstract The structures, first-, second-, and third-order polarizabilities for the linear hydrogen-bonded p-nitroaniline systems 1a – 5a and related systems 2b – 5b are calculated by the use of ab initio and PM3 semiempirical methods. The difference of ab intio and PM3 calculated OH hydrogen bond distances between NO 2 and NH 2 groups for 2a , 3a , 2b , and 3b are 0.31, 0.31, 0.18, and 0.27, respectively. The PM3-predicted frequency dependent asymptotic values of γ for the frequencies of 0.0eV, 0.25eV, and 0.5eV are 5.3e5, 5.7e5, and 7.4e5 10 −36 esu in the linear types, respectively. The linear hydrogen bonded p-nitroaniline systems exhibit power law dependences with the exponents 1.5852, 1.5946, and 1.6272, repectively.