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A novel ion separation methodology using a cation-exchange membrane modified with iron oxide nanoparticles (Fe3O4 NPs) coated with polyhexamethylene guanidine (PHMG) is proposed. The separation is performed in an electrodialysis cell, where firstly phosphate is electro-adsorbed to the PHMG@Fe3O4 NP coating, followed by a desorption step by applying an electric current. [ABSTRACT FROM AUTHOR]

Abstract We have investigated in detail properties of hybrid polyelectrolyte-anion exchange membranes (AEMs) having different amounts of a guanidinium-modified poly(allylamine hydrochloride) (PAH-Gu) derivative (2, 5, and 8 wt%). The presence of guanidinium groups at the membrane surface was confirmed by XPS. For 2 and 5 wt% the blended membranes are homogeneous, while at 8 wt% segregation is observed by AFM. The membrane permselectivity and ionic electrical resistance for phosphate reduce upon incorporation of the PAH-Gu in the membrane, reflecting an increased co-ion (H+ and Na+) permeation. We conclude that PAH-Gu loaded in the AEM favors an interaction with phosphate. In electrodialysis, using sodium sulfate and sodium dihydrogen phosphate at equal concentrations in the source phase a slight preference for phosphate was observed. Our work shows that this facile membrane fabrication procedure shows great potential in terms of tuning the membrane properties. One way to boost selective ion transport could be by increasing the number of functional groups in the membrane. [ABSTRACT FROM AUTHOR]

Novel bio-based and biodegradable electrospun membranes, containing bactericidal ricinoleic acid (RA) units either by copolymerization with butylene succinate (BS) units or by blending PRA and PBS homopolymers, are characterized in their chemical, thermal, mechanical and surface properties. In the blends E. coli and S. aureus mortality rate increases with PRA amount, while the copolymer shows lower bactericidal activity compared to the blend with similar composition. XPS demonstrates that in the blends an enrichment of RA units at the fiber surface occurs during electrospinning due to phase separation, while in the copolymer RA units are homogeneously dispersed along fiber cross-section. [ABSTRACT FROM AUTHOR]

In this work, the effectiveness of atmospheric pressure non-equilibrium plasma, generated by a dielectric barrier discharge and operated in air, in successfully crosslinking water soluble pullulan electrospun fibers is demonstrated. After being exposed to plasma, the fibers show a remarkable capability to preserve structural stability and fiber morphology upon water exposure. The gel fraction and the water absorption are quantified to evaluate the crosslinking efficiency of different plasma operating conditions, and ATR-FTIR characterization provided some insights into plasma-induced modification of pullulan chemical structure. [ABSTRACT FROM AUTHOR]

We report an advanced treatment method for phosphoric acid recovery from leached sewage sludge ash. Layer-by-layer (LbL) polyelectrolyte deposition has been used as a tool to modify and convert a hollow ultrafiltration membrane into a nanofiltration (NF) LbL membrane for H 3 PO 4 recovery. To build the LbL membrane, poly(styrenesulfonate) PSS was chosen as polyanion, while three different polycations were used: a permanently charged polyelectrolyte, poly(diallyldimethylammonium chloride), PDADMAC; a pH-dependent charged polyelectrolyte poly(allylamine hydrochloride), PAH; and a PAH modified with guanidinium groups (PAH-Gu). Based on detailed surface characterizations (AFM, XPS and Zeta-potential) it was concluded that both charge density and pH-responsiveness of the polycations are key parameters to control the final membrane surface structure and transport properties. The surface properties of LbL-coated membranes were correlated with the membrane filtration performance, when exposed to the real leached sewage sludge ash solution. The highest permeability was recorded for (PDADMAC/PSS) 6 , a result that was rationalized on its loose, and possibly less interpenetrated, structure, followed by (PAH-Gu/PSS) 6 characterized by a more dense, compact layer. H 3 PO 4 recovery was the highest in the case of (PDADMAC/PSS) 6 , but the retention of multivalent metals (Fe3+ and Mg2+) was low, leading to a more contaminated permeate. The opposite trend was observed for (PAH-Gu/PSS) 6, resulting in a less metal-contaminated, but also a less H 3 PO 4 -concentrated permeate. Our LbL-modified membranes were found to improve the permeability and H 3 PO 4 recovery compared to a commercially available acid-resistant NF membrane. Image 1 • Layer-by-layer NF membranes recover H 3 PO 4 from leachate sewage sludge ash. • Permeability: LbL-coated membranes > commercial acid-resistant NF membranes. • Type of polycation in LbL coatings affects separation properties. • Largest H 3 PO 4 recovery for permanent polycation, but low Fe3+ and Mg2+ retention. • Weaker polycation with guanidinium moiety: less metal and less H 3 PO 4 in permeate. [ABSTRACT FROM AUTHOR]

The recovery of carboxylic acids from fermentation broth is one of the main bottlenecks for the industrial production of bio-based esters. This paper proposes an alternative for the recovery of carboxylates produced by fermentations at pH values above the pKa of the carboxylic acid. In this approach, the aqueous carboxylate anion is recovered using anion exchange, followed by desorption and esterification with CO2-expanded alcohols. Using CO2-expanded methanol, we achieved a high desorption yield at 10 bar of CO2 and 20 °C. An ester yield of 1.03 ± 0.07 mol methyl acetate/acetatein was obtained for the combined desorption–esterification at 5 bar of CO2 and 60 °C. The proposed process has low chemical consumption and low waste production. The proposed process works, with a lower yield, for other carboxylates (e.g. lactate and succinate) and alcohols (e.g. ethanol). [ABSTRACT FROM AUTHOR]

• Poly(l -lactic acid) electrospun fibers loaded with struvite crystals were prepared. • PLLA fibers loaded with struvite can recover nutrients (N and P) from solution. • Struvite dispersion and location along the fiber section affect nutrient recovery. • The biodegradable nanostructured mat can be employed as ready-to-use fertilizer. One of the greatest global challenges of the 21st century is facing the depletion of phosphorous reserves, widely used in fertilizers. One possibility is to recover the phosphorous discharged in the water by human activities, with the consequent additional benefit of improving water quality by limiting eutrophication. In this work, biodegradable poly(l -lactic acid) (PLLA) nonwovens produced by electrospinning are proposed as highly porous fibrous materials characterized by high surface-to-volume ratio for promoting the crystallization of struvite crystals as a means to recover both phosphorus and nitrogen from a nutrient rich solution. To this aim, PLLA fibers were intentionally loaded with a small amount of struvite crystals (3,7 wt%) by applying different preparation procedures, including sonication steps, single-nozzle and coaxial electrospinning. PLLA fibers containing struvite crystals were immersed in a synthetic solution of suitable ions to investigate the occurrence of struvite accumulation through the analysis of the soaked nonwovens with several techniques, i.e. Scanning and Transmission Electron Microscopy, Wide Angle X-Ray Diffraction, Thermogravimetric analysis and Atomic Emission Spectrometry. We demonstrated that struvite loaded in the PLLA fibers successfully acted as crystal seeds and enabled the precipitation of struvite crystals firmly attached to fiber surface. Results showed that the quality of crystal seeds dispersion in PLLA fibers as well as their location along the fiber section heavily affect struvite recovery. Prospectively, these materials can be directly used, after being in contact with wastewater and enriched with struvite, as ready-to-use fertilizers. [ABSTRACT FROM AUTHOR]