Low-pressure reverse osmosis membrane made of cellulose nanofiber and carbon nanotube polyamide nano-nanocomposite for high purity water production

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-11, Vol.448, p.137359, Article 137359
• Main Authors: Fajardo-Diaz, J.L., Morelos-Gomez, A., Cruz-Silva, R., Ishii, K., Yasuike, T., Kawakatsu, T., Yamanaka, A., Tejima, S., Izu, K., Saito, S., Maeda, J., Takeuchi, K., Endo, M.
• Format: Article
• Language: English
• Subjects: Boron rejection; Carbon nanotube; Cellulose nanofiber; High purity water; Nanocomposite film; Si rejection
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2022.137359

The good integration between the carbon nanotubes and cellulose nanofibers to a thin film polymeric matrix (PA-CNT/CNF) increased the anti-scaling performance for ions like Si, Ca, Na in a low-pressure reverse osmosis process. Changes in the chemical surface state, an increase on the hydrophobic surface, and modifications on the amount of oxygen and nitrogen functionalities at the surface promotes salt rejections ∼99.47 % and water flux ∼1.6 m3/m2day, very competitive performance for brackish water filtration and high purity water production compared with commercial membranes and modules. [Display omitted] •Cellulose carbon fibers -carbon nanotube polyamide nano composite membrane.•Membrane maintains high salt rejection and high-water flux at low-pressure RO.•Increase of hydrophobics, surface oxygen, and reduction of surface roughness.•Cellulose nanofibers promoted higher permeation in combination with PA-CNT structure.•Boosted performance for Si, Na, Ca rejection compared with commercial modules. Cellulose nanofiber (CNF) and multiwall carbon nanotube (CNT) nanocomposite polyamide membranes were synthesized and used in a low-pressure reverse osmosis (RO) system. Incorporating CNT and CNF into the polyamide structure (PA-CNT/CNF) allows the homogenous dispersion within the polymeric matrix, increasing its hydrophobic character and surface oxygen functionalities while reducing its surface roughness when compared to plain polyamide (PA), PA-CNT, and PA-CNF membranes. The resultant nanocomposite was tested at 0.75 MPa and sodium chloride salt concentration of 500 ppm resulting in a rejection of 99.47 % and water permeability of 1.65 m3/m2day. The rejection and permeation performance is highly competitive compared with commercial RO membranes. A 2in spiral module built with the PA-CNT/CNF membrane and tested for SiO2, NaCl, and CaCl2 rejection showed a reduction in its permeability of 24.9 % after 100 h of operations, while the commercials showed a decrease of 49.42 %. The present RO membrane module achieved a calcium rejection of 97.5 % and a boron rejection of 50.4 %. The 2in PA-CNT/CNF spiral module was tested in a two-step RO filtration system for high pure water (HPW) production and compared with a TW30 module with NSF certification. The PA-CNT/CNF module revealed a permeability reduction of 9.07% after 30 h operation, while TW30 had a reduction of 20.3%, which is about twice the durability. Molecular dynamics simulation showed that the CNF increased wate