TY - JOUR
T1 - Transport of target anions, chromate (Cr (VI)), arsenate (As (V)), and perchlorate (CIO4-), through RO, NF, and UF membranes
AU - Yoon, J.
AU - Amy, G.
AU - Yoon, Y.
PY - 2005
Y1 - 2005
N2 - Rejection and transport of chromate (Cr (VI)), arsenate (As (V)), and perchlorate (CIO4-) by and through reverse osmosis, nanofiltration, and ultrafiltration were found to be affected by solution pH and ionic strength. In this study, the rejection of these target ionic contaminants increased with increasing pH at the same conductivity (ionic strength) for the tested membranes, regardless of salt type. General trends showed that the rejection followed the order: CaCl2 < KCI ≤ K2SO4, at the same pH and conductivity condition. The rejection also significantly decreased as conductivity was increased regardless of the salt type. These results support the notion that a more negative surface charge due to increasing pH and/or decreasing ionic strength (conductivity) enhances rejection; lower molecular weight cut-off also enhances rejection. Measured values of hindered diffusion coefficient through the membrane pores (Dp) for the target contaminants significantly decreased as pH was increased, regardless of salt type at the same conductivity. At the same pH and conductivity, the Dp of the target contaminants follows the order: CaCl2 > KCI > K2SO4, in the presence of different types of salts. The Dp of the target contaminants significantly increased as conductivity was increased regardless of the salt type. The rejection data were modeled by application of a non-equilibrium thermodynamic model. The rejection model has five transport parameters: the molecular transport coefficient (ω), osmotic pressure gradient (Δ∏), molecular reflection coefficient (σ), the average bulk fluid interfacial concentration between the feed and permeate side (Cavg), and the solvent flux (Jv). The transport parameters were determined by independent measurements (and calculation with minimum assumptions.) Measurements and predictions of the target contaminant transport were in good agreement.
AB - Rejection and transport of chromate (Cr (VI)), arsenate (As (V)), and perchlorate (CIO4-) by and through reverse osmosis, nanofiltration, and ultrafiltration were found to be affected by solution pH and ionic strength. In this study, the rejection of these target ionic contaminants increased with increasing pH at the same conductivity (ionic strength) for the tested membranes, regardless of salt type. General trends showed that the rejection followed the order: CaCl2 < KCI ≤ K2SO4, at the same pH and conductivity condition. The rejection also significantly decreased as conductivity was increased regardless of the salt type. These results support the notion that a more negative surface charge due to increasing pH and/or decreasing ionic strength (conductivity) enhances rejection; lower molecular weight cut-off also enhances rejection. Measured values of hindered diffusion coefficient through the membrane pores (Dp) for the target contaminants significantly decreased as pH was increased, regardless of salt type at the same conductivity. At the same pH and conductivity, the Dp of the target contaminants follows the order: CaCl2 > KCI > K2SO4, in the presence of different types of salts. The Dp of the target contaminants significantly increased as conductivity was increased regardless of the salt type. The rejection data were modeled by application of a non-equilibrium thermodynamic model. The rejection model has five transport parameters: the molecular transport coefficient (ω), osmotic pressure gradient (Δ∏), molecular reflection coefficient (σ), the average bulk fluid interfacial concentration between the feed and permeate side (Cavg), and the solvent flux (Jv). The transport parameters were determined by independent measurements (and calculation with minimum assumptions.) Measurements and predictions of the target contaminant transport were in good agreement.
KW - Arsenate
KW - Chromate
KW - Hindered diffusion
KW - Negatively charged membrane
KW - Perchlorate
UR - http://www.scopus.com/inward/record.url?scp=21244501359&partnerID=8YFLogxK
U2 - 10.2166/wst.2005.0653
DO - 10.2166/wst.2005.0653
M3 - Article
C2 - 16003993
AN - SCOPUS:21244501359
SN - 0273-1223
VL - 51
SP - 327
EP - 334
JO - Water Science and Technology
JF - Water Science and Technology
IS - 6-7
ER -