Boric acid removal with polyol-functionalized polyether membranes

• Published in: Journal of membrane science 2021-11, Vol.638, p.119690, Article 119690
• Main Authors: Landsman, Matthew R., Rivers, Frederick, Pedretti, Benjamin J., Freeman, Benny D., Lawler, Desmond F., Lynd, Nathaniel A., Katz, Lynn E.
• Format: Article
• Language: English
• Subjects: Boron; MATERIALS SCIENCE; N-methyl-d-glucamine; Poly(allyl glycidyl ether); Selective capture; Water reuse
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2021.119690

Poor selectivity of conventional desalination membranes for boron often necessitates multi-stage treatment trains to achieve desired boron removal for end uses such as irrigation. One approach to membrane design for improved single-pass boric acid removal is via incorporation of chelating ligands that selectively sorb boron. In this study, membranes based on epoxy-amine cross-linked poly(glycidyl glycidyl ether) (PGGE) were synthesized and functionalized with N-methyl-d-glucamine (NMDG), a polyol known to interact selectively with boron. PGGE and PGGE-NMDG membranes exhibited boron sorption isotherms that were well-described by dual mode isotherms. PGGE-NMDG sorbed 2.5 mmol B/g dry polymer from a neutral aqueous solution containing 100 mmol B/L, which was almost three times the adsorption density of a commercial boron selective resin, Amberlite IRA743. The membranes were regenerated in acid without a significant loss of boron sorption capacity over four cycles. Interactions between boron and NMDG and PGGE sites (e.g., epoxides) impacted boron diffusion in both membranes. The use of ligand functionalized membranes to capture target solutes such as boron requires high loading of interacting sites to maximize uptake capacity. Establishing fundamental structure/property rules for boron selectivity could lead to new material designs with improved boron separation properties for water purification. [Display omitted] •PGGE membranes were synthesized and functionalized with NMDG for boron removal.•Boron sorption in the membranes was reversible and exhibited dual mode behavior.•Boron diffusion was influenced by specific interactions with PGGE and NMDG sites.•Boron capture by polyol membranes requires high capacities or frequent regeneration.