High performance ligands for the removal of aqueous boron species by continuous polymer enhanced ultrafiltration

• 3 new polymers were studied as boron complexing agents in ultrafiltration setup.
• Effects of parameters like loading and pH on boron retention have been studied.
• N-methyl-D-glucamine functional group showed the best results in literature.
• Not only the number of functional groups but also the structure is important.

Boron is an essential element for plant growth, but it may also result in toxicity when present in excessive amounts. In this study, continuous polymer enhanced ultrafiltration (PEUF) was developed to selectively recover aqueous boron species (collectively termed “boron” hereafter) from solution. The PEUF process consisted of complexing boron to a water-soluble polymer, removing all non-complexed solutes by UF, restoring the unloaded polymer, and isolating the newly freed boron by UF. Three different polymers were synthesized to complex boron. One was derived from N-meth-yl-D-glucamine (P1). Two others were derived from iminodipropyleneglycol (P2 and P2G). Operating parameters such as the boron/polymer ratio (0.01–1), pH value (7–10), and polymer type (P1, P2, and P2G) were assessed. An increase of the pH value led to increased boron retention. As well, a decreased loading value enhanced retention. A maximum retention of 90.1% exceeded the highest values reported in the literature under similar conditions. The permeate flux remained constant at ≈ 20 L/m2 h, and operation was unaffected by classic problems such as fouling. The results showed that continuous PEUF utilizing the above polymers could serve as an alternative method for the removal of environmental boron.