Search

The present study highlights the influence of support and monomer properties on the performance of thin-film composite (TFC) membranes. For this purpose, a series of polyamide-cellulose acetate thin-film composite nanofiltration (TFC-NF) membranes were prepared by interfacial polymerization technique using cellulose acetate (CA) membrane as support and the monomer of cyclohexane-1,3,5 tricarbonylchloride (HTC) as an organic phase. The effect of the cellulose acetate concentration on the pore size of the membrane support was investigated using 15%, 16.5%, 18%, 19.5%, and 21.5% of cellulose acetate. m-phenylenediamine (MPD), piperazidine (PIP), and 1,3- cyclohexanebis (methylamine) (CHMA) were studied as monomers. Results displayed that PIP/HTC membrane is more hydrophilic and has more intense granular and convex structure with rougher surface compared to the other prepared membranes. The water flow and the porosity depended on the cellulose acetate concentration. The decrease in porosity complied well with permeability, contact angle, and SEM analysis. The membrane performances were evaluated for the retention of NaCl, CaCl, and NaSO retention. Comparing the NaSO rejection with CaCl and NaCl, the former is higher than the latter.

The aim of this work has been treat Cr- rich groundwaters through membranes processes as alternative to conventional methods. Chromium (Cr) is a dangerous element for environment and human health. Commonly, the highest concentrations Cr are detected in ophiolitic areas where ultramafic and serpentinite rocks crop up and the weathering processes of these rocks are the main cause of Cr-rich groundwaters in worldwide. The sample water taken into account comes from Bonassola serpentinitic aquifer (La Spezia, Liguria, Italy) and the Cr concentration detected are 84 μg/l. This value is above to the WHO threshold for drinking water set to 50 μg/L and moreover starting from 1 January 2019 the potability threshold value for Cr (VI) was lowered to 10 μg (D.M. 06/07/2017) by Italian government. In this regards, NF/RO laboratory-scale system with membrane modules named DK (proprietary thin-film), AD (polyamide) and CD (cellulose acetate) were used to treating polluted groundwater and experiments were conducted at different operating pressure The treatment have shown a lowering of Cr concentration within the threshold values with rejection around 95%. These preliminary results are quite promising for future developments on Cr removal from contaminated groundwater in the world.

Fluoropolymer membranes are applied in membrane operations such as membrane distillation and membrane crystallization where hydrophobic porous membranes act as a physical barrier separating two phases. Due to their hydrophobic nature, only gaseous molecules are allowed to pass through the membrane and are collected on the permeate side, while the aqueous solution cannot penetrate. However, these two processes suffer problems such as membrane wetting, fouling or scaling. Membrane wetting is a common and undesired phenomenon, which is caused by the loss of hydrophobicity of the porous membrane employed. This greatly affects the mass transfer efficiency and separation efficiency. Simultaneously, membrane fouling occurs, along with membrane wetting and scaling, which greatly reduces the lifespan of the membranes. Therefore, strategies to improve the hydrophobicity of membranes have been widely investigated by researchers. In this direction, hydrophobic fluoropolymer membrane materials are employed more and more for membrane distillation and membrane crystallization thanks to their high chemical and thermal resistance. This paper summarizes different preparation methods of these fluoropolymer membrane, such as non-solvent-induced phase separation (NIPS), thermally-induced phase separation (TIPS), vapor-induced phase separation (VIPS), etc. Hydrophobic modification methods, including surface coating, surface grafting and blending, etc., are also introduced. Moreover, the research advances on the application of less toxic solvents for preparing these membranes are herein reviewed. This review aims to provide guidance to researchers for their future membrane development in membrane distillation and membrane crystallization, using fluoropolymer materials.

The shortage of clean water sources and increase of demand for fresh water have become as major global challenges not only in industries but also inhuman life. Meanwhile, membrane technology has been extensively noticed due to high separation efficiency, energy-saving and environmentally-friendly characteristic. So, development of new membrane is a vital step in advancing of membrane application in water-treatment. This paper presents a comprehensive review on development of high-performance nanofiltration membrane based on nanotechnology for wastewater treatment. Application of new nanomaterials has enabled fabrication of NF-membranes with improved separation properties for pollutants removal from water. Recognizing that conventional membranes are not necessarily suitable for industrial applications and/or process intensifications many attempts were made recently to use of nanomaterials into NF-membranes, aiming to overcome trade-off relationship between flux/selectivity and to improve their stability. So, development of new structured nanomaterial with desirable properties is one of most crucial research topics for membrane researchers. Accordingly, an overview on different methods to design of advanced nanomaterial presented that allow us to overcome their inherent problems in membranes fabrication such as agglomeration, defects formation, insufficient pores’ tuning, poor active sites and anti-fouling properties; however, selection of appropriate nanomaterials is a challenge of utmost difficulty. Various types of nanomaterials such as zeolites, carbon based, framework (MOF/ZIF/COF), nano-biopolymers and special nanoparticles such as SFNPs, SFNCs, POSS, ZCPs, and nickel hydroxide nanosheet are presented and their roles in NF-transport are discussed as well as strategies for surface modification of nanoparticles to promoting their surface charges density. Moreover, fabrication methods of nano enhanced NF-membranes including layer by layer assembly, hollow fiber spinning, electrospinning of nanofibers, construction of thin-film nanocomposite besides blending, co-polymerization; cross-linking and grafting techniques are discussed. A proper view for selection of appropriate nanoparticles in membrane fabrication is offered while considering types of pollutants to be removed.

Membrane separation has been widely used for various applications including microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) processes in the fields of biomedicine, food, and water purification. In this work, a facile synthesis of new polyamide thin-film composite nanofiltration membranes (NF-TFC) for water purification was described. The polyamide thin film was deposed over a synthetic cellulose acetate (CA) support by interfacial polymerization method. 1,3 cyclohexane bis (methylamine) (CHMA) and trimesoyl chloride (TMC) were used as monomers. The membranes were characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy (FT-IR), water uptake, porosity, contact angle, water permeability and rejection towards specific salt and dye molecules. The effect of the variation of the CHMA concentration (0.2–2 wt.%) on the morphology, porosity, water permeation and rejection properties of the prepared membranes was studied. SEM results displayed the growth of the membrane thickness when the CHMA concentration increased from 0.2 to 2 wt.%. The strong adhesion between the cellulose acetate substrate and the polyamide layer explained by the formation of the polyamide film in the substrate surface and inside the pores. The water permeability varied from 36.02 to 17.09 L h−1 m−2 bar−1. The salt rejection of Na2SO4 and NaCl increased from 9 to 68% and from 38.41% to 89.4%, respectively, when the CHMA concentration was changed from 0.2 to 2 wt.%. The prepared membranes were further applied successfully for the removal of malachite green and congo red. The results indicated that the maximum rejection reached 89% and 85% for malachite green and congo red, respectively.

Biodegradation is among the most common issues affecting Cultural Heritage stone materials in outdoor environments. In recent years, the application of chemical agents with biocidal activity has been the most usual practice when dealing with biofilm removal. In outdoor environments, the use of these biocides is not effective enough, since the materials are constantly exposed to environmental agents and atmospheric pollutants. Thus, it becomes necessary to protect the surface of Cultural Heritage works with antimicrobial coatings to either prevent or at least limit future colonization. In this study, innovative biocides—both natural and synthetic—were applied on a Roman mosaic located in the Archaeological Park of Ostia Antica to compare their effectiveness in removing the biological degradation affecting it. In addition, an antimicrobial coating called “SI-QUAT” was applied and analyzed in situ. SI-QUAT has recently entered the market for its prevention activity against biocolonization. The biocidal activity of these products was tested and monitored using different analytical portable instruments, such as the multispectral system, the spectrocolorimeter, and the bioluminometer. The analyses showed that promising results can be obtained using the combination of the biocide and the protective effect of Preventol® RI50 and SI-QUAT.

Polymer membranes have attracted interest in many areas, such as desalination, water treatment, gas separation, and energy storage and generation. Membrane fabrication requires large amounts of solvents for polymer dissolution. These solvents often show toxicity and need to be replaced by greener solvents to avoid adverse effects on human health and increase sustainability of the production processes. The need to use non-toxic compounds is increasing with the strong growth of the global membrane market. This review focuses on green solvents and green materials to prepare polymer-based membranes for the steadily increasing range of applications. Membrane fabrication techniques, choice of emerging green solvents, economic evaluation, and application areas will be comprehensively and critically reviewed. This review provides important selection guidelines for greener solvents for chemists, chemical engineers, and material scientists, focusing on organic chemicals and polymer processing. Furthermore, a simple cost analysis for a typical green solvent is provided, and its impact on the membrane fabrication cost is discussed. This journal is