title: Use of surfactant modified ultrafiltration for perchlorate (Cl(O)(4-)) removal.
abstract: Determinations of perchlorate anion (ClO(4)(-)) transport and rejection were performed using a surfactant modified ultrafiltration (UF) membrane. Perchlorate anion (at a concentration of 100 microg/L of ClO(4)(-), spiked with KClO(4)) was introduced to the membrane as a pure component, in binary mixtures with other salts, cationic and anionic surfactants, and at various ionic strength conditions (conductivity). Also, a natural source water was spiked with perchlorate in the presence of cationic and anionic surfactants and used to determine the effects of a complex mixture (including natural organic matter (NOM)) on the observed rejection. All filtration measurements were performed at approximately the same permeate flow rate in order to minimize artifacts from mass transfer at the membrane interface. The objective of this study was to modify a negatively charged UF membrane in terms of the fundamental mechanisms, steric/size exclusion and electrostatic exclusion and to enhance perchlorate rejection, with synthetic water and a blend of Colorado River water and State Project water (CRW/SPW). Previous work suggested that perchlorate was dominantly rejected by electrostatic exclusion for charged nanofiltration (NF) and UF membranes (Rejection of perchlorate by reverse osmosis, nanofiltration and ultrafiltration (UF) membranes: mechanism and modeling. Ph.D. dissertation, University of Colorado, Boulder, USA, 2001). In that research, perchlorate rejection capability was quickly lost in the presence of a sufficient amount of other ions. However, this study showed that ClO(4)(-) was excluded from a (negatively) charged UF membrane with pores large with respect to the size of the ion. Although perchlorate rejection capability due to apparent electrostatic force was reduced in the presence of a cationic surfactant, a desired amount of the ClO(4)(-) was excluded by steric exclusion. The steric exclusion was due to decreasing membrane pore size caused by the adsorption of the cationic surfactant.
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado, ECOT 441, Boulder 80309, USA.
authors.forename: Jaekyung
authors.initials: J
authors.lastname: Yoon
authors.forename: Yeomin
authors.initials: Y
authors.lastname: Yoon
authors.forename: Gary
authors.initials: G
authors.lastname: Amy
authors.forename: Jaeweon
authors.initials: J
authors.lastname: Cho
authors.forename: David
authors.initials: D
authors.lastname: Foss
authors.forename: Tae-Hyung
authors.initials: TH
authors.lastname: Kim
mesh_terms: D005374:Filtration; D010472:Perchlorates / Q000737:chemistry / Q000302:isolation & purification*; D017670:Sodium Compounds / Q000737:chemistry / Q000302:isolation & purification*; D055672:Static Electricity; D013501:Surface-Active Agents / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D010472:Perchlorates; D017670:Sodium Compounds; D013501:Surface-Active Agents; C031068:sodium perchlorate