Boron Rejection Research Articles

Thin-film nanocomposite reverse osmosis membranes incorporated with citrate-modified layered double hydroxides (LDHs) for brackish water desalination and boron removal

By intercalating citrate anions into the inter-layer of layered double hydroxides (LDHs), the inter-layer spacing of the resultant CA-Mg-LDH is enlarged from 7.5 to 11.8 Å. With the aid of this newly developed CA-Mg-LDH, novel thin-film nanocomposite (TFN) membranes have been prepared, systematically investigated, and demonstrated for brackish water reverse osmosis (BWRO) desalination. By manipulating the nanofiller concentration, a water permeance of 3.21 LMH bar−1 and a salt rejection of 98.9% are obtained for the TFN membrane at the optimal loading of 0.15 wt%. It achieves a 68% higher water permeance than the pristine TFC membrane but without notably sacrificing the selectivity, owing to the moderate enlargement of the inter-layer spacing of CA-Mg-LDH. In addition, this novel TFN membrane has a boron rejection of 75% when using a 2000 ppm NaCl solution containing 10 ppm boron as the feed at 20 bar. This work is the first attempt to use CA-Mg-LDH as nanofillers in TFN membranes for demonstration of BWRO and boron removal, offering new insights and strategies for the design of next-generation TFN membranes for water treatment.

Pressure-driven membrane processes for boron and arsenic removal: pH and synergistic effects

This study analyzed novel synergistic effects on rejection of arsenic and boron during membrane-based treatment. The effect of pH on rejection was characterized for pure and mixed arsenate, arsenite and borate (As(V), As(III), and B respectively) solutions. The favorable effect of high pH was strongest for B and As(III) due to the similar charge evolution in the pH 7–11 range. While only significant for arsenate, both arsenic species exhibited higher rejections when boron was present. Analysis of watersheds in southern Peru revealed a correlation between arsenic and boron; synthetic river water containing 10 mg/L B (0.97 mmol/L) and 1 mg/L As (0.013 mmol/L) was subsequently tested. Both reverse osmosis (BW30) and nanofiltration membranes (NF90) produced a system permeate that complied with the WHO standards (1 mg/L B and 0.01 mg/L As) above pH 9 in these representative, contaminated waters. The combination of increasing the pH from 7 to 9.5 and the synergistic effect doubled the allowable concentration of As(V) in the feed for BW30 from 0.5 mg/L to 1.0 mg/L. In addition to informing treatment of surface and ground waters, findings could be applied to the reuse of high pH gold cyanidation wastewaters and enhancing boron rejection during seawater desalination.

Flux-enhanced reduced graphene oxide (rGO)/PVDF nanofibrous membrane distillation membranes for the removal of boron from geothermal water

• When the rGO concentration was increased, permeate flux was enhanced in AGMD system. • The optimum rGO concentration was described as 0.039 wt% according to membrane characterization such as contact angle, liquid entry pressure (LEP). • Compared to bare PVDF membrane, boron rejection was enhance using modified membrane with 0.039 wt% rGO. • It was obtained that less than 0.5 mg/L boron concentration in permeate water. In this work, fabrication of PVDF nanofiber membrane with reduced graphene oxide (rGO) using electrospinning technique has been carried out to improve AGMD performance. Membrane morphology and different membrane characteristics such as contact angle, thickness, liquid entry pressure (LEP), young module, scanning electron microscopy (SEM) and surface roughness of membrane were analyzed for the characterization of hydrophobic nanofiber membranes. Firstly, rGO/PVDF membranes with different rGO concentrations were produced using the electrospinning method. All fabricated rGO/PVDF membranes were characterized and used in the AGMD system for the treatment of saline water. Secondly, the selected optimum membrane according to characterization and filtration results was used in the AGMD system for the treatment of synthetic and real geothermal water. Results showed that all rGO membranes exhibit higher permeate water flux and salt rejection, lower permeate boron or salt concentration than pure PVDF membrane. In real geothermal water experiments, rGO/PVDF membrane (0.039 wt%) were improved permeate water flux from 19.20 to 30 L/m 2 .h, boron rejection from 96.89% to 98.16%. Also, permeate boron concentration was decreased using rGO/PVDF membrane (0.039 wt%) from 0.305 mg/L to 0.226 mg/L. As a result, fabricated rGO/PVDF membranes were achieved to the enhanced performance of the AGMD system.

Boron and salt ion transport in electrically assisted reverse osmosis

Herein, we report a novel electrically assisted reverse osmosis (EARO) process which integrates an electrochemical process with the conventional RO process. We systematically investigated the behaviors of boron and salt ion (i.e., Na+ and Cl−) transporting through a commercial seawater RO (SWRO) membrane in the EARO process under a range of applied voltages by employing an external porous carbon cloth as cathode on the SWRO membrane surface. The SWRO membrane in the EARO process exhibited a significantly enhanced boron rejection of 93.8% under the applied voltage of 4 V compared with the conventional RO process (~75.0%). The enhancement in boron removal efficiency in EARO is mainly attributed to the locally elevated pH near the RO membrane surface caused by water electrolysis. At elevated pH, boron transforms from the uncharged boric acid to negatively charged and sized-increased borate ion and is more favorably rejected by the SWRO membrane. On the other hand, the variation of salt ion rejection was marginal with increasing the applied voltages in EARO. This study demonstrates that the EARO has a great potential to achieve low-chemical and low-cost boron removal in one-pass RO seawater desalination. To make this process more practically feasible, the future efforts need to optimize the development of the electrically conductive feed spacer and the membrane module.

Performance evaluation and boron rejection in a SWRO system under variable operating conditions

It is well known that reverse osmosis (RO) is the leading desalination technology. As an energy intensive technology, the exploitation of renewable energy sources (RES) to power RO systems is a attractive option. A strategy to take advantage of all the available energy of an off-grid renewable system is to work with the RO system under variable operating conditions. This implies additional challenges in terms of water production and permeate quality, among others. Boron rejection is one of the main concerns in seawater RO (SWRO) systems. The aim of this work was to evaluate the performance and boron rejection of a single-stage SWRO system with 7 membrane elements per pressure vessel under variable operating conditions. The initial permeability coefficients of two SWRO membranes (TM820L-440 and TM820S-400) were calculated from experimental data of a full-scale SWRO desalination plant. These coefficients and the characteristics of the membranes were introduced in a simulation algorithm to estimate the behavior of the SWRO system. The results show that, compared with the TM820S-400 membrane, the TM820L-440 performed better in terms of boron rejection in the form of boric acid, but worse in terms of water production. When RES-powered SWRO systems are designed to work under variable operating conditions, consideration needs to be given to the safe operation window in terms of boron concentration in the permeate and to variation of the permeability coefficient of the membranes.

Towards a High Rejection Desalination Membrane: The Confined Growth of Polyamide Nanofilm Induced by Alkyl-Capped Graphene Oxide.

In this paper, we used an octadecylamine functionalized graphene oxide (ODA@GO) to induce the confined growth of a polyamide nanofilm in the organic and aqueous phase during interfacial polymerization (IP). The ODA@GO, fully dispersed in the organic phase, was applied as a physical barrier to confine the amine diffusion and therefore limiting the IP reaction close to the interface. The morphology and crosslinking degree of the PA nanofilm could be controlled by doping different amounts of ODA@GO (therefore adjusting the diffusion resistance). At standard seawater desalination conditions (32,000 ppm NaCl, ~55 bar), the flux of the resultant thin film nanocomposite (TFN) membrane reached 59.6 L m−2 h−1, which was approximately 17% more than the virgin TFC membrane. Meanwhile, the optimal salt rejection at seawater conditions (i.e., 32,000 ppm NaCl) achieved 99.6%. Concurrently, the boron rejection rate was also elevated by 13.3% compared with the TFC membrane without confined growth.

Produced water desalination using high temperature membranes

Produced water is the largest source of wastewater in the oil and gas industry. One of the approaches to manage excess produced water is to increase its reuse opportunities using desalination technologies such as reverse osmosis. This article presents an experimental study using high temperature reverse osmosis membranes to treat produced water in a relatively high temperature range. Synthetic water was prepared using the produced water formula containing 10,600 mg/L of Total Dissolved Solids (TDS) and 83 mg/L of boron. Different pH and temperature conditions were evaluated to simulate the field operation conditions. The selected membrane module demonstrated high boron rejection at the test condition of pH 11 in the temperature range of 25 °C–60 °C. More than 98% of boron rejection was achieved at the maximum testing temperature of 60 °C. The membrane software was calibrated with the lab test data. Further lab studies using field produced water at 55 °C showed consistent results for boron and TDS rejections. Calibrated membrane software was used to perform system-level design at various recovery rates; the projected water quality and pressures had good alignment with the lab test results. The consistent membrane performance in this study provides an opportunity to undertake future field study using the RO membranes to treat high temperature produced water.

Thin-film nanocomposite membrane comprised of a novel phosphonic acid derivative of titanium dioxide for efficient boron removal

The separation of toxic boron from seawater is the main concern for the desalination industries. The membrane-based boron separation is challenging due to the existence of boron in the neutral boric acid form. According to World Health Organization, a Boron above 0.5 ppm is not recommended for human health and agricultural use. The design of NF membranes for the Boron separation is tricky due to its neutral charge. In this study, a novel modification of titanium dioxide (TiO2) nanoparticles is performed by reacting with the cyclic propyl phosphonic anhydride (T3P) reagent in the presence of triethylamine as a base to obtain the phosphonic acid derivative of TiO2 (PTiO2). The PTiO2 was used as inorganic filler during the coating of the polyamide layer on the ultrafiltration support. Better dispersion of the nanoparticles was achieved due to the effective interactions between the –POOH (of PTiO2) and –NH2 (of meta-phenylene diamine groups) as evidenced by the ATR-IR spectrum. The resultant nanocomposite membranes showed a high potential to reject scalant divalent ions (>98%) and sodium chloride (>60%) with improved permeation characteristics. The boron adsorption study revealed a strong adsorption of boric acid ~12 mg/g by the PTiO2 nanoparticles causing the pore narrowing effect. Due to the same reason, the boron diffusion coefficient of the membranes reduced at neutral pH. The boron rejection offered by the membrane with 0.1 wt% PTiO2 was ~2.5 times higher than the commercial NF90 membrane.

Reproductive toxicity and metabolic perturbations in male rats exposed to boron

The poor rejection of boron (B) by reverse osmosis, a dominant seawater desalination and household-scale water treatment technology, is a critical issue given its potential adverse effects on human health and the extensive and increasing application of seawater desalination facilities worldwide. Although previous in vivo studies have revealed the reproductive toxicity of B, the mechanistic underpinnings and changes in the global metabolome remains undefined. To systematically investigate the effects of B on male reproduction and endogenous metabolic fingerprints, adult male rats were exposed to different doses of borax (25, 50 and 100 mg B/kg/day) for 28 days via oral gavage. After mating the treated rats with untreated female rats, we found a significant reduction in the proportion of live foetuses only in the highest dose group (100 mg B/kg/day) compared with the control group (treated with deionised water). Furthermore, compared with the control group, the concentration of plasma follicle-stimulating hormone increased and the activities of testicular enzymes (malate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase) were significantly upregulated in the 100 mg B/kg/day group, whereas the activity of testicular sorbitol dehydrogenase and the concentrations of plasma interleukin-5 were inversely proportional to the doses and were the lowest at the highest dose of 100 mg B/kg/day. The concentrations of testicular hormones (e.g., oestrone, oestradiol, oestriol, testosterone, cortisol and androstenedione) were significantly upregulated in the rats exposed to 100 mg B/kg/day. Non-targeted metabolomics and lipidomics revealed a significant disruption of lipid and amino acids metabolism at the highest dose, particularly that of linoleic acid, α-linolenic acid, sphingolipid, glycerolipid, glycerophospholipid, branched-chain amino acid and nicotinate metabolism, and unsaturated fatty acids synthesis, which are predominantly associated with inflammation, antioxidation defence, energy utilisation, steroid hormone synthesis and lipid abnormalities. Our results offer insights into the mechanisms underlying the adverse effects of B on reproduction and into the health risks posed by drinking desalinated seawater that containing elevated B concentrations.

Boron rejection from aqueous solution and wastewater by direct contact membrane distillation

Boron is widely used in various areas of modern technology. Due to the environmental problems arising during the production and use, the studies on the removal and recovery of boron from wastewater have been increased recently. Membrane distillation (MD) system is smaller in size with respect to other common distillation systems and needs lower operating temperatures. In addition, the equipment costs are reduced and the safety of the process increases since it operates at lower pressures. Moreover, the membrane distillation process can remove pollutants from water without using chemicals. In this study, boron rejection from aqueous solutions and wastewater was investigated by using direct contact membrane distillation (DCMD) system where both surfaces of a porous hydrophobic membrane were in contact with liquid streams. The effects of various parameters (pH, feed concentration, feed temperature, etc.) on boron rejection were investigated and the highest boron rejection was found to be 50 % when pH=10 at 50 °C and with feeding by a pump of 54 rpm. According to the test results of wastewater from Kırka Borax treatment plants, the mean distillate fluxes were found as 13, 16 and 14 L m-2 h-1 at the feed temperatures of 30, 40 and 50 °C, respectively. The boron removal percentages were found to be 47, 64 and 48 % at 30, 40 and 50 °C, respectively. It was observed in the XRD spectra that the crystals in wastewater mainly consist of Na2B(OH)4Cl and Mg2B2O5 structures.

Practical Considerations of Wastewater-Seawater Integrated Reverse Osmosis: Design Constraint by Boron Removal.

The wastewater–seawater (WW-SW) integrated reverse osmosis (RO) process has gained much attention in and out of academia due to its energy saving capability, economic benefits, and sustainability. The other advantage of this process is to reduce boron concentration in the RO permeate that can exclude the post-treatment process. However, there are multiple design constraints regarding boron removal that restrict process design in the WW-SW integrated system. In this study, uncertainties in design factors of the WW-SW integrated system in consideration of boron removal have been explored. In comprehensive consideration of the blending ratio of between WW and SW, regulatory water quality standard, specific energy consumption (SEC), specific water cost, and RO recovery rate, a range of 15,000~20,000 mg/L feed turned out to be the most appropriate. Furthermore, boron rejection tests with SWRO (seawater reverse osmosis) and BWRO (brackish water reverse osmosis) membranes under actual WW-SW integration found a critical reduction in boron rejection at less than 20 bar of operating pressure. These findings emphasize the importance of caution in the use of BWRO membranes in the WW-SW integrated RO system.

The influence of RO membrane surface properties on surfactant fouling in radioactive wastewater treatment

Reverse osmosis (RO) has been shown to be an efficient treatment method for radioactive wastewater, which has been employed in nuclear power plants. However, the fouling on RO membrane surface should be solved to fabricate modified RO membranes with selective and fouling-resistant surface, which is essential for the further widespread application of RO. To provide fundamental insights into fouling control methods, the influence of surface properties on surfactant fouling was investigated with modified RO membranes. The results showed that surfactant fouling reduced the flux of RO membranes by 35 %–75 %. The interfacial free energies associated with the surfactants and RO membranes surface were calculated by XDLVO theory to explain surfactant fouling mechanisms. The interfacial free energies associated with CTAB and RO membrane surface increased from 3.18 to 41.22 and 69.62 mJ m−2 and SDBS increased from 20.21 to 34.07 and 43.97 mJ m−2, Tween 80 increased from -2.63 to 3.98 and 9.61 mJ m−2 with PEI and EPTAC grafting. The results indicated that the changes of interfacial free energies were mainly caused by the changes of membrane hydrophilicity and surface charge. Fabricating RO membrane with hydrophilic and neutrally charged surface was potential for improving all kinds of surfactants resistant capability. Besides, surfactant fouling had great influence on membrane permeability. The changes of radioactive nuclide rejections were mainly caused by the changes of membrane surface charge while the increase of boron rejection was attributed to the rise of membrane surface steric-hindrance. Therefore, the membrane hydrophilicity and surface charge should be carefully considered in radioactive wastewater containing surfactants treatment.

Study of the Influence of Temperature on Boron Concentration Estimation in Desalinated Seawater for Agricultural Irrigation

After several decades, the incorporation of desalinated seawater into agricultural areas with scarce water resources has become one of the main water supply strategies. Compared to the several currently available desalination techniques, reverse osmosis (RO) is now the reference technology because it lowers energy uses and production costs. Nevertheless, its main limiting factor lies in the membranes used for this system not efficiently retaining boron, which is a problem because the concentration of this element in seawater is high. For 3 years, the present work analysed the impact of seawater temperature on the kinetic parameters of boron rejection in an RO system to establish their annual behaviour and the existing correlation between both parameters. A comparison was made using the values simulated in the projection software provided by the manufacturer of the membranes. The obtained results indicated a high correlation, and the R2 correlation coefficients came very close to the unity. Nonetheless, this correlation lowered with time due to typical membrane ageing and compaction because of the system’s continuous operation. Under the tested working conditions and by applying analysed temperature intervals, it was impossible to reach the 0.3 mg·L−1 boron concentration value that ensures lack of crop toxicity. Thus, incorporating other boron reduction techniques is necessary.

Influence of pH and NaCl concentration on boron rejection during nanofiltration

Nanofiltration (NF) is promising for replacing reverse osmosis for boron removal more effectively and at a higher energy efficiency. However, the interplay of steric and charge effects underlying rejection behaviors of solutes smaller than the membrane pore size remained incompletely understood, which impedes implementation. This study investigated the influence of pH and NaCl concentration on boric acid/borate rejection by the Desal 5DK NF membrane, with acetic acid/acetate (comparable size and charge nature) and glucose (larger and neutral) serving as benchmarks. Filtration experiments demonstrate that varying pH in the range of 3–11 and NaCl concentration up to 100 mM had little effect on glucose rejection (consistently greater than 95%), but affected the two smaller solutes significantly. Increasing pH from 7 to 11 led to 15% higher rejection of charged acetate because of the increased charges of both the membrane and solute, while increasing pH from 3 to 7 gave 30% higher rejection of neutral boric acid due to steric effects stemming from pore-size reduction. The rejections of the neutral boric acid and acetic acid were negligibly affected by NaCl concentration, but rejection decreased by 15% and 50% for the charged borate and acetate, respectively, due to salt-induced pore-swelling.

The separation of radionuclides and silicon from boron-containing radioactive wastewater with modified reverse osmosis membranes

The ability to reuse boron and minimize the volume of radioactive waste could be accomplished with modified reverse osmosis (RO) membranes. RO membranes were fabricated via polyethylenimine (PEI) grafting to separate silicon and radionuclides from boron-containing radioactive wastewater. The positively charged RO membrane promoted more efficient removal of nuclides and silicon while the rejection of boron declined from 55.88 % to 41.71 % after modification. Compared with virgin RO membrane, the SFB-Si, SFB-Cs, and SFB-Co of the modified RO membranes increased from 6.02, 5.16, and 12.62–29.52, 61.91, and 547.15, respectively. SFB-Si, SFB-Cs, and SFB-Co of the simulated RO system with modified RO membranes further increased to 156.96, 1068.12, and 83617.88, respectively. As a result, permeate water with 433.92mgL−1 boron, 0.04mgL−1 silicon, 1.62μg·L−1 Cs(I), and 0.02μg·L−1 Co(II) was obtained, which could satisfy radionuclide treatment requirements and allow for the reuse of boron. Overall, modified RO membranes would be able to reuse boron and minimize the volume of discharge of radioactive wastewater.

Biomimetic artificial water channel membranes for enhanced desalination.

Inspired by biological proteins, artificial water channels (AWCs) can be used to overcome the performances of traditional desalination membranes. Their rational incorporation in composite polyamide provides an example of biomimetic membranes applied under representative reverse osmosis desalination conditions with an intrinsically high water-to-salt permeability ratio. The hybrid polyamide presents larger voids and seamlessly incorporates I-quartet AWCs for highly selective transport of water. These biomimetic membranes can be easily scaled for industrial standards (>m2), provide 99.5% rejection of NaCl or 91.4% rejection of boron, with a water flux of 75 l m-2 h-1 at 65 bar and 35,000 ppm NaCl feed solution, representative of seawater desalination. This flux is more than 75% higher than that observed with current state-of-the-art membranes with equivalent solute rejection, translating into an equivalent reduction of the membrane area for the same water output and a roughly 12% reduction of the required energy for desalination.

P.672 Serum nerve growth factor levels in children with specific learning disorder

To comprehensively investigate the correlation between free volume properties (size and distribution) in the interior of polyamide (PA) active layer and mass transport mechanism, six polyamide thin film composite (TFC) membranes were characterized using positron annihilation lifetime spectroscopy (PALS). In case of pressurized filtration conditions, the rejection rate of boron across all PA membranes was found to be inversely proportional to the free volume size. The more boron transport occurred at the membrane containing larger free volume. In addition, the transition of the neutral boron transport mechanism from convection to diffusion was found to occur at a membrane free volume radius around 0.275 nm within the applied pressure range (2 and 10 bar), as verified by PALS and the dimensionless Peclet number. We believe that mass transport mechanism transition from convection to diffusion is caused by the compression of polyamide active layer due to applied hydraulic pressure (10 bar), resulting in lowering the convective mass transport pathway inside polyamide active layer. These membrane free volume size criteria and experimental filtration results may subsequently be used as new design guidelines for the development of high boron rejection polyamide TFC membranes having a low energy consumption.

Utilization of Nano-TiO2 as an Influential Additive for Complementing Separation Performance of a Hybrid PVDF-PVP Hollow Fiber: Boron Removal from Leachate.

The continuous increase in anthropogenic activities resulting in an increase in boron concentration in the environment is becoming a serious threat to public health and the ecosystem. In this regard, a hybrid polyvinylidene fluoride (PVDF)-polyvinyl pyrrolidone (PVP) hollow fiber was synthesized with hydrophilic nano-titanium oxide (TiO2) at varied loadings of 0, 0.5, 1.0, 1.5, and 2.0 wt% using the phase inversion technique. The resultant membranes were characterized in terms of Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), contact angle, porosity, and zeta potential. The permeability flux was assessed using both pure water and leachate; also, rejection performance was evaluated based on boron removal from the leachate. The results revealed that the membrane with 1.0 wt% loading had the highest flux alongside an upturn in boron rejection percentage of 223 L/m2·h and 94.39%, respectively. In addition, the lowest contact angle of 50.01° was recorded with 1.0 wt% TiO2 loading, and this implies that it is the most hydrophilic. Throughout the experiment cycles, the fiber with 1.0 wt% TiO2 loading demonstrated a high flux recovery varying between 92.82% and 76.26% after 9 h filtration time. The physicochemical analysis of the permeate revealed that the boron concentration was significantly reduced to 0.43 mg/L, which is far lower than the discharge limit of 1.0 mg/L.

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

AbstractBACKGROUNDReverse 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)

Experimental investigation of forward osmosis process for boron removal from water

Forward osmosis technology is one of the most rapidly developing processes of desalination and water treatment. The transport of boron in forward osmosis (FO) using various FO membranes was investigated in this study. Three specific membranes — an FTS H2O™ membrane, a PSU membrane and an Aquaporin Inside™ membrane — were applied to study the impact of the feed solution (FS) pH, boron concentration, and draw solution (DS) concentration on boron solute flux, boron rejection and water flux. The results indicated an increment in boron solute flux with increasing DS and boron concentration but a reduction with increasing FS pH. Moreover, increasing the FS pH from 4 to 10 enhanced the rejection rate of boron from 12% to 90% for the FTS H2O™ membrane, from 8% to 84% for the PSU membrane and from 8% to 76% for the Aquaporin Inside™ membrane. With increment in the DS concentration from 0.5 to 3 M, the rejection rate of boron increased from 20% to 54% for the FTS H2O™ membrane, from 14% to 50% for the PSU membrane and from 8% to 40% for the Aquaporin Inside™ membrane. Apparently, increasing the boron concentration in the FS did not have a significant effect on boron rejection. The boron rejection rate was approximately 20–30% for the Aquaporin Inside™ membrane, 32–40% for the FTS H2O™ membrane and 25–35% for the PSU membrane.