In-Situ Modification of Nanofiltration Membranes Using Carbon Nanotubes for Water Treatment.

Modification of thin-film composite (TFC) nanofiltration (NF) membranes to increase permeability and improve separation performance remains a significant challenge for water scarcity. This study aimed to enhance the permeability and selectivity of two commercial polyamide (PA) NF membranes, NF90 and NF270, by modifying them with carbon nanotubes (CNTs) using microwave (MW)-assisted in-situ growth. The conducting polymer, polypyrrole (Ppy), and a ferrocene catalyst were used to facilitate the growth process. Chemical and morphological analyses confirmed that the surface of both membranes was modified. The NF270-Ppy-CNT membrane was selected for ion rejection testing due to its superior permeability compared to the NF90-Ppy-CNT. The modified NF270 membrane showed a 14% increase in ion rejection while maintaining constant water permeability. The results demonstrated that it is feasible to attach CNTs to a polymeric surface without compromising its functional properties. The Spliegler-Kedem model was employed to model the rejection and permeate flux of NF270-Ppy-CNT and NF270 membranes, which indicated that diffusive transport contributes to the modification to increase NaCl rejection. The present study provides a promising approach for modifying membranes by in-situ CNT growth to improve their performance in water treatment applications, such as desalination.

Optimization of detergents in solubilization and reconstitution of Aquaporin Z: A structural approach.

BACKGROUND: The exceptional capacities of aquaporins in terms of water permeation and selectivity have made them an interesting system for membrane applications. Despite the multiple attempts for immobilizing the aquaporins over a porous substrate, there is a lack of studies related to the purification and reconstitution steps, principally associated with the use of detergents in solubilization and destabilization steps. This study analyzed the effect of detergents in Aquaporin Z solubilization, considering the purity and structural homogeneity of the protein. METHODS: The extraction process was optimized by the addition of detergent at the sonication step, which enabled the omission of the ultracentrifugation and resuspension steps. Two detergents, Triton X-100, and octyl-glucoside were also evaluated. Destabilization mediated by detergents was used as reconstitution method. Saturation and solubilization points were defined by detergent concentration and both, liposomes and proteoliposomes, were analyzed by size distribution and permeability assays. Detergent removal with Bio-beads was also analyzed. RESULTS: Octyl glucoside ensures structural stability and homogeneity of Aquaporin Z. However, high concentrations of detergents induce the presence of defects in proteoliposomes. While saturated liposomes create homogeneous and functional structures, solubilized liposomes get affected by a reassembly process, creating vesicle defects with anomalous permeability profiles. CONCLUSIONS: Detergent concentration affects the structural conformation of proteoliposomes in the reconstitution process. GENERAL SIGNIFICANCE: Since the destabilization process is dependent on vesicle, detergent, and buffer composition, optimization of this process should be mandatory for further studies. All these considerations will allow achieving the potential of Aquaporins and any other integral membrane protein in their applications for industrial purposes.

Fourier-transform infrared imaging and multivariate analysis for direct identification of principal polysaccharides in brown seaweeds.

The current hydrocolloid industry requires new techniques for biomass characterization, which can quickly and ecologically characterize contained sugars. This work proposes the use of Fourier Transform Infrared microspectroscopy in combination with multivariate methods, to localize and identify the main carbohydrates and other components present in fresh brown seaweeds, avoiding time-consuming samples pre-treatments. Infrared images of Macrocystis pyrifera samples were analyzed by Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) and Principal Component Analysis (PCA) as chemometrics techniques to identify the compounds. MCR-ALS was the best strategy, delivering pure spectra of chemical compound that PCA did not. The carbohydrates identified by this method were 1-3-ß-glucans divided into endofibers and laminarin; two types of fucoidans (rich in fucose or mannuronic acid), alginate and mannitol, besides other compounds such as proteins. This technique represents an opportunity for the hydrocolloid industry for a modern, rapid and environmentally-friendly characterization of macroalgal biomass to enhance its use.