Development and Industrial-Scale Fabrication of Next-Generation Low-Energy Membranes for Desalination

Spiral-wound modules have been the most common configuration of packing flat-sheet membranes since the early development of polyamide (PA) membranes for water treatment applications. Conventional spiral-wound modules (SWMs) for desalination applications typically consist of several leaf sets, with each leaf set comprising feed spacers, membranes, and a permeate carrier (PC) wrapped around a permeate-collecting tube. The membrane area that can be packed into a given module diameter is limited by the overall leaf set thickness, restricting module productivity for a given membrane permeability. We describe here a novel industrial-scale method for successfully coating the polysulfone (PSf) ultrafiltration (UF) support layer directly onto a permeate carrier, instead of conventional non-woven fabric, as a precursor to the polyamide TFC coating, resulting in twofold benefits: (a) drastically simplifying the membrane fabrication process by eliminating the use of non-woven fabric and (b) increasing the throughput of each membrane module by facilitating the packing of a larger membrane area in a standard module housing. By combining the permeate carrier and membrane into a single sheet, the need for the non-woven support layer was eliminated, leading to a significantly reduced leaf set thickness, enabling a much larger membrane area to be packed in a given volume, leading to lower energy consumption per cubic meter of produced water. Molecular-weight cutoff (MWCO) values in the range of 36–96 kDa were found to be dependent on PC thickness and material. Nevertheless, the reinforced membranes were successfully fabricated with a ~9% reduction in membrane leaf thickness compared to a conventional membrane. Preliminary trials of coating a thin-film composite PA layer resulted in defect-free reverse osmosis (RO) membranes with a salt rejection of 94% and a flux of 40 L m⁻² h⁻¹ when tested against a 2000 mg/L NaCl feed solution at an operating pressure of 15 bar. Results from the testing of the 1812 and 2514 elements validated the novel concept and paved the way for further improvements towards full-scale RO membranes with the potential to be the next low-energy workhorse of the water industry.

Novel Sandwich-Structured Hollow Fiber Membrane for High-Efficiency Membrane Distillation and Scale-Up for Pilot Validation

Hollow fiber membranes were produced from a commercial polyvinylidene fluoride (PVDF) polymer, Kynar HSV 900, with a unique sandwich structure consisting of two sponge-like layers connected to the outer and inner skin layers while the middle layer comprises macrovoids. The sponge-like layer allows the membrane to have good mechanical strength even at low skin thickness and favors water vapor transportation during vacuum membrane distillation (VMD). The middle layer with macrovoids helps to significantly reduce the trans-membrane resistance during water vapor transportation from the feed side to the permeate side. Together, these novel structural characteristics are expected to render the PVDF hollow fiber membranes more efficient in terms of vapor flux as well as mechanical integrity. Using the chemistry and process conditions adopted from previous work, we were able to scale up the membrane fabrication from a laboratory scale of 1.5 kg to a manufacturing scale of 50 kg with consistent membrane performance. The produced PVDF membrane, with a liquid entry pressure (LEPw) of >3 bar and a pure water flux of >30 L/m2·hr (LMH) under VMD conditions at 70−80 °C, is perfectly suitable for next-generation high-efficiency membranes for desalination and industrial wastewater applications. The technology translation efforts, including membrane and module scale-up as well as the preliminary pilot-scale validation study, are discussed in detail in this paper.

Effect of ranolazine on glycaemic control in patients with type 2 diabetes treated with either glimepiride or metformin

AIM

To report the results of two phase III trials assessing the efficacy of ranolazine for glycaemic control in patients with type 2 diabetes on metformin or glimepiride background therapy.

METHODS

In two double-blind trials we randomized 431 and 442 patients with type 2 diabetes to ranolazine 1000 mg twice daily versus placebo added to either glimepiride (glimepiride add-on study) or metformin background therapy (metformin add-on study). Patients receiving ranolazine added to metformin had their metformin dose halved (with the addition of a metformin-matched placebo) relative to the placebo group to correct for a metformin-ranolazine pharmacokinetic interaction. The primary endpoint of the trials was the change from baseline in glycated haemoglobin (HbA1c) at week 24.

RESULTS

When added to glimepiride, ranolazine caused a 0.51% least squares mean [95% confidence interval (CI) 0.71, 0.32] decrease from baseline in HbA1c at 24 weeks relative to placebo and roughly doubled the proportion of patients achieving an HbA1c of <7% (27.1 vs 14.1%; p = 0.001). When added to metformin background therapy, there was no significant difference in the 24-week HbA1c change from baseline [placebo-corrected LS mean difference -0.11% (95% CI -0.31, 0.1)].

CONCLUSIONS

Compared with placebo, addition of ranolazine in patients with type 2 diabetes treated with glimepiride, but not metformin, significantly reduced HbA1c over 24 weeks. The decreased dose of metformin used in the metformin add-on study complicates the interpretation of this trial. Whether an effective regimen of ranolazine added to metformin for glycaemic control can be identified remains unclear.