A Novel Multi-Charged Draw Solute That Removes Organic Arsenicals from Water in a Hybrid Membrane Process

The potential of forward osmosis for water treatment can only be maximized with suitable draw solutes. Here a three-dimensional, multicharge draw solute of decasodium phytate (Na₁₀-phytate) is designed and synthesized for removing organic arsenicals from water using a hybrid forward osmosis (FO) – membrane distillation (MD) process. Efficient water recovery is achieved using Na₁₀-phytate as a draw solute with a water flux of 20.0 LMH and negligible reverse solute diffusion when 1000 ppm organic arsenicals as the feed and operated under ambient conditions with FO mode. At 50 °C, the novel draw solute increases water flux by more than 30% with water fluxes higher than 26.0 LMH on the FO side, drastically enhancing water recovery efficiency. By combining the FO and MD processes into a single hybrid process, a 100% recovery of Na₁₀-phytate draw solute was achieved. Crucially, organic arsenicals or Na₁₀-phytate draw solutes are both rejected 100% and not detected in the permeate of the hybrid process. The complete rejection of both organic arsenicals and draw solutes using hybrid membrane processes is unprecedented; creating a new application for membrane separations

Comparing the environmental impacts of using bio-renewable and fossil-derived solvent in polymer membrane fabrications

Sustainable production methods for polymer membrane fabrication are gaining attention due to concerns about the toxicity of conventional fossil-derived solvents in the production process. In addition, the promotion of using chemicals from renewable source for synthesis processes among industries and researches has increased to decelerate resource depletion. As such, more benign and bio-renewable solvents, dihydrolevoglucosenone (Cyrene™) and 2-methyltetrahydrofuran (2-MeTHF), have been proposed as replacements for traditional fossil-derived solvents, n-hexane and dimethylformamide (DMF). In this work, a life cycle assessment (LCA) was employed to quantitatively evaluate the environmental impacts of using the aforementioned bio-renewable solvents versus fossil-derived solvents for fabricating 1 g of polymer membrane. The analysis adopted a cradle-to-gate perspective and assessed three endpoint impact categories: Human health, Ecosystems and Resources. Despite lower environmental impacts for producing bio-renewable solvents, using such solvents to fabricate membranes displayed a higher environmental impact score in all endpoint categories. This discrepancy was attributed to the lower yield of the membrane fabrication process when using bio-based solvents. This indicated that further work is needed to optimise membrane fabrication so that the benefits of using bio-based solvents can be maximised

Molecular design of nanohybrid gas separation membranes for optimal CO2 separation

10.1016/j.polymer.2011.12.011Polymer532454-465POLM

Spray-assisted assembly of thin-film composite membranes in one process

Spray coating has been exploited to fabricate and tailor the morphologies of various components in thin film composite membranes separately. For the first time, here we exploit this technology to construct and assemble both the selective layer and porous support of a thin-film composite membrane in a single process. In our approach, spray-assisted non-solvent induced phase inversion and interfacial polymerization reduced the time required to fabricate thin-film composite membranes from 3 – 4 days to 1 day and 40 mins. Our approach did not sacrifice membrane separation performances during desalination of a mixture comprising 2000 ppm of NaCl in water at 4 bar and room temperature. At these conditions, compared to traditional thin film composite membranes, the water permeance of our spray coated membranes was higher by 35.7 %, reaching 2.32 L m-2 h-1 bar-1, while achieving a NaCl rejection rate of 94.7 %. This demonstrated the feasibility of fabricating thin film composites via spray coating in a single process, potentially reducing fabrication time during scale-up production