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Sustainable textile wastewater treatment strongly demands an indispensable paradigm shift from removal of contaminants to effective recovery of resources. In this work, a hybrid tight ultrafiltration (TUF) and bipolar-membrane electrodialysis (BMED) process was explored to recover resources (i.e., dye extraction, acid/base conversion, and pure water regeneration) from highly saline textile wastewater. Using a TUF membrane with 5000 Da molecular weight cutoff (MWCO) can obtain a sufficient rejection (>99.6%) of both reactive and direct dyes, due to the dye aggregation. Additionally, the considerably large pore size of the TUF membrane endowed the process with free transport of NaCl and Na2SO4 (i.e., >99.42%), exhibiting promise as an alternative means of separation of dyes and Na2SO4. Additionally, an integrated TUF-based diafiltration was designed to separate the model dye (i.e., reactive blue 194) and Na2SO4. Particularly, reactive blue 194 was remarkably concentrated from 997.9 to 7952.8 mg·L–1 by the TUF membrane with 99.5% dye recovery and 99.95% desalination efficiency after 8.0 diavolumes. Furthermore, a trace amount (i.e., 2.7 mg·L–1) of reactive blue 194 was observed in Na2SO4-containing TUF permeate, enabling a subsequent BMED operation. With the implementation of BMED, the Na2SO4-containing TUF permeate was sufficiently desalinated for acid/base conversion and pure water regeneration with no obvious fouling on the ion exchange membranes. These results demonstrate a potential applicability of the hybrid TUF/BMED process for sustainable management of textile wastewater, providing a strategy for practical applications in treatment of other high-salinity wastewaters.

The potential of a membrane crystallizer equipped with a BW-30 reverse osmosis membrane has been investigated for recovering Na 2 CO 3 from aqueous streams, targeting its application in CO 2 mitigation. The effect of various crystallization conditions, such as the concentration of the osmotic solution, the concentration of the Na 2 CO 3 solution, as well as membrane orientations on the process performance has been systematically determined. This dense membrane crystallizer was thought to be better than the membrane contactor applied in previous work due to its higher water flux, marked as 0.210 L·m −2 ·h −1 in forward osmosis (FO) mode and 0.164 L·m −2 ·h −1 in pressure retard osmosis (PRO) mode compared with 0.08 L·m −2 ·h −1 for the membrane contactor. Compared with the PRO mode, the FO mode was found to be a better alternative with higher water permeability and draw solute rejection. The concentration of the osmotic solution was the key parameter to condition the applicability of this system. The long-term operation of the system can be realized without any membrane damage and fouling. In addition, Na 2 CO 3 ·10H 2 O crystals were obtained with a superhigh purity of 99.98%. Therefore, this osmotic crystallizer equipped with a dense membrane was proven to be an effective alternative for Na 2 CO 3 crystallization for the application in CO 2 capture process.

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