Boron removal with modified polyamide RO modules by cross‐linked glutaric dialdehyde grafting

Abstract

BACKGROUNDReverse osmosis (RO) plays an increasingly important role in boron removal. In this study, novel polyamide RO membranes and modules with high boron rejection were fabricated by cross‐linked glutaric dialdehyde (GA) grafting. To evaluate the influence of GA grafting on membrane materials, the surface properties before and after modification were analyzed.RESULTSThe results showed that the membrane morphology changed distinctly after GA modification. All modified membranes became more hydrophilic as the water contact angle decreased from 60° to 35°. The zeta potential of RO membrane surface increased from −6.23 mV to 17.27 mV, which indicated that the surface charge altered from negative to positive. The rejection of boron increased from 76.65% to 90.14% and the boron permeability coefficient decreased from 3.71 to 0.79. Furthermore, the rejection of boron for modified module was >90% over a 5–22 ppm range of boron concentration. The rejection of boron also stabilized at ≈90% beyond 3000 min.CONCLUSIONThe modified RO membrane modules with high boron rejection and acceptable flux could be used in boron removal. The approach in this study can improve the separation properties of boron for commercially available modules without disassembling. © 2020 Society of Chemical Industry (SCI)

A review of zeolite materials used in membranes for water purification: history, applications, challenges and future trends

“…In addition, uncharged boric acid has a vacant p-orbital that by accepting free electrons is able to make hydrogen bonds between the hydroxyl groups in boric acid and charged active layer of membrane surfaces resulting in non-ionic diffusion of boron through RO membranes and a low boron removal rate. 26,27 Moreover, the correlation between the free volume (size and distribution) of the polyamide layer and boron rejection was confirmed and the results indicated that a lower boron rejection can be observed for the larger free volume in the top layer of the membranes. 28 To mitigate the challenges in using conventional polyamide TFC membranes, various strategies such as modification of the polyamide layer, incorporation of nanoparticles (NPs) or the manipulation of the IP procedure have been explored.…”

“…15,23 Another challenge of current polyamide TFC membranes is their fairly low boron removal rate by single-pass RO systems to comply with the World Health Organization standard for drinking water to ensure a lack of toxicity for aquatic life and human health. [24][25][26] Boron in seawater (moderate pH level) forms boric acid with an estimated radius of 0.155 nm and unique physicochemical properties similar to those of water molecules. In addition, uncharged boric acid has a vacant p-orbital that by accepting free electrons is able to make hydrogen bonds between the hydroxyl groups in boric acid and charged active layer of membrane surfaces resulting in non-ionic diffusion of boron through RO membranes and a low boron removal rate.…”

Effect of feed water composition and pretreatment on the irrigation water for boron-sensitive crops

“…Similar to the situation at natural pH, coarse-filtered feed delivered higher boron rejections compared to fine-filtration. This situation may be attributed to denser membrane surface due to particulate matter deposition that has potential for scaling, and boron-containing ionic compounds [45]. At pH 9.5, the RO membrane performed stable rejections throughout the study lasting for 8 h. Although salt and silica rejections were fairly in the same range, their concentrations in permeates obtained from both fine and coarse filtrated feeds were higher than the ones obtained at natural pH (Figure 10).…”

Development of seawater reverse osmosis membranes for efficient desalination and boron removal

“….... 49 diagram for the preparation of hexafluoroalcohol-containing aromatic PA bilayer membrane (La et al 2013). (d) Surface modification of RO membrane by cross-linked glutaric dialdehyde (GA) grafting (Chen et al 2020). (e) Proposed reaction mechanism by chlorinated treatment (Zhai et al 2011) Fig.…”

“…This enhancement can be attributed to the increased inherent thickness of the PA active layer and the controlled hydrophobic plugging impact. innovative TFC-RO membrane and modules with exceptional boron rejection were successfully developed through the grafting of cross-linked glutaric dialdehyde (GA) (Chen et al 2020). The boron rejection soared from 76.65% to an impressive 90.14%, while the boron permeability coefficient experienced a noticeable decline from 3.71 to a mere 0.79.…”