TY - JOUR
T1 - Divalent Cation Removal by Donnan Dialysis for Improved Reverse Electrodialysis
AU - Rijnaarts, Timon
AU - Shenkute, Nathnael T.
AU - Wood, Jeffery A.
AU - de Vos, Wiebe M.
AU - Nijmeijer, Kitty
N1 - ACS deal
PY - 2018/5/7
Y1 - 2018/5/7
N2 - Divalent cations in feedwater can cause significant decreases in efficiencies for membrane processes, such as reverse electrodialysis (RED). In RED, power is harvested from the mixing of river and seawater, and the obtainable voltage is reduced and the resistance is increased if divalent cations are present. The power density of the RED process can be improved by removing divalent cations from the fresh water. Here, we study divalent cation removal from fresh water using seawater as draw solution in a Donnan dialysis (DD) process. In this way, a membrane system with neither chemicals nor electrodes but only natural salinity gradients can be used to exchange divalent cations. For DD, the permselectivity of the cation exchange membrane is found to be crucial as it determines the ability to block salt leakage (also referred to as co-ion transport). Operating DD using a membrane stack achieved a 76% reduction in the divalent cation content in natural fresh water with residence times of just a few seconds. DD pretreated fresh water was then used in a RED process, which showed improved gross and net power densities of 9.0 and 6.3%, respectively. This improvement is caused by a lower fresh water resistance (at similar open circuit voltages), due to exchange of divalent for monovalent cations.
AB - Divalent cations in feedwater can cause significant decreases in efficiencies for membrane processes, such as reverse electrodialysis (RED). In RED, power is harvested from the mixing of river and seawater, and the obtainable voltage is reduced and the resistance is increased if divalent cations are present. The power density of the RED process can be improved by removing divalent cations from the fresh water. Here, we study divalent cation removal from fresh water using seawater as draw solution in a Donnan dialysis (DD) process. In this way, a membrane system with neither chemicals nor electrodes but only natural salinity gradients can be used to exchange divalent cations. For DD, the permselectivity of the cation exchange membrane is found to be crucial as it determines the ability to block salt leakage (also referred to as co-ion transport). Operating DD using a membrane stack achieved a 76% reduction in the divalent cation content in natural fresh water with residence times of just a few seconds. DD pretreated fresh water was then used in a RED process, which showed improved gross and net power densities of 9.0 and 6.3%, respectively. This improvement is caused by a lower fresh water resistance (at similar open circuit voltages), due to exchange of divalent for monovalent cations.
KW - UT-Hybrid-D
KW - Calcium
KW - Magnesium
KW - Cation exchange membrane
KW - Donnan dialysis
KW - Reverse electrodialysis
KW - Hardness removal
UR - http://www.scopus.com/inward/record.url?scp=85046703709&partnerID=8YFLogxK
U2 - 10.1021/acssuschemeng.8b00879
DO - 10.1021/acssuschemeng.8b00879
M3 - Article
SN - 2168-0485
VL - 6
SP - 7035
EP - 7041
JO - ACS sustainable chemistry & engineering
JF - ACS sustainable chemistry & engineering
IS - 5
ER -