Improving Ion Rejection of Conductive Nanofiltration Membrane through Electrically Enhanced Surface Charge Density.
Environ Sci Technol
; 53(2): 868-877, 2019 01 15.
Article
em En
| MEDLINE
| ID: mdl-30540165
ABSTRACT
Nanofiltration (NF) is considered a promising candidate for brackish and seawater desalination. NF exhibits high multivalent ion rejection, but the rejection rate for monovalent ions is relatively low. Besides, great challenges remain for conventional NF membranes to achieve high ion rejection without sacrificing water flux. This work presents an effective strategy for improving the ion rejection of conductive NF membrane without decreasing the permeability through electrically assisted enhancement of surface charge density. When external voltage is increased from 0 to 2.5 V, the surface charge density of the membrane increases from 11.9 to 73.0 mC m-2, which is 6.1× higher than that without external voltage. Correspondingly, the rejection rate for Na2SO4 increases from 81.6 to 93.0% and that for NaCl improves from 53.9 to 82.4%; meanwhile, the membrane retains high permeabilities of 14.0 L m-2 h-1 bar-1 for Na2SO4 filtration and 14.5 L m-2 h-1 bar-1 for NaCl filtration. The Donnan steric pore model analysis suggests that the Donnan potential difference between the membrane and bulk solution is increased under electrical assistance, leading to increased ion transfer resistance for improved ion rejection. This work provides new insight into the development of advanced NF technologies for desalination and water treatment.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Purificação da Água
/
Membranas Artificiais
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article