Development of novel grafted hybrid PVA membranes using glycidyltrimethylammonium chloride for pervaporation separation of water–isopropanol mixtures

Fabrication of cellulose-collagen based biosorbent as eco-friendly scavengers for uranyl ions

The aim of the present research is to fabricate a biosorbent using agricultural waste for removal of uranium from contaminated water i.e. "waste to wealth" approach. Cellulose extracted from wheat straw was mercerized and a novel semi-interpenetrating polymer network (semi-IPN) was fabricated through graft copolymerization of polyvinyl alcohol onto hybrid mercerized cellulose + collagen backbone. Response surface methodology was used for optimization of different reaction parameters as a function of % grafting (195.1 %) was carried out. Semi-IPN was found to possess higher thermal stability. Adsorption results revealed that the optimum parameters for the elimination of uranium using semi-IPN were: adsorbent dose = 0.15 g, pH = 6.0, contact time = 120 min and initial U (VI) concentration = 100 μg/L. The pseudo-second-order kinetic model gave the best description of the adsorption equilibrium data as the calculated qe value is nearest to the experimental qe for the different initial U(VI) concentrations. Adsorption experiments followed Langmuir isotherm with R2 = 0.999. Furthermore, recyclability and reusability studies showed that the adsorption efficiency of semi-IPN was 82 % after 5 cycles indicating the superior recycling execution of fabricated biosorbent. Thus, the fabricated ecofriendly device can be used effectively for the removal of uranium from contaminated wastewater sources.

Development of Novel Membranes Based on Polyvinyl Alcohol Modified by Pluronic F127 for Pervaporation Dehydration of Isopropanol

Membrane methods are environmentally friendly and can significantly improve the design and development of new energy consumption processes that are very important nowadays. However, their effective use requires advanced membrane materials. This study aims to improve the performance of pervaporation polyvinyl alcohol (PVA)-based membrane for isopropanol dehydration. To achieve this goal, two methods were applied: (1) bulk modification of PVA by Pluronic F127 and (2) development of supported PVA-based membrane using polyphenylene isophthalamide (PA) as a substrate with a various porosity. Developed membranes were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), contact angle measurement, and swelling experiments. The concentration influence of PA casting solution (12–20 wt.%) on the performance of porous PA membranes (substrates) was investigated in ultrafiltration of pure water and bovine serum albumin (BSA) solution as well as by microscopic methods (SEM and atomic force microscopy). The developed dense and supported PVA-based membranes were tested in the pervaporation dehydration of isopropanol. Optimal transport characteristics were obtained for a supported membrane with a PVA-based selective layer containing 3 wt.% Pluronic F127 onto an ultrafiltration PA (17 wt.%) substrate: improved permeation flux 0.100–1.164 kg/(m2 h) and 98.8–84.6 wt.% water content in the permeate in pervaporation dehydration of isopropanol (12–80 wt.% water).

Surface Properties, Free Volume, and Performance for Thin-Film Composite Pervaporation Membranes Fabricated through Interfacial Polymerization Involving Different Organic Solvents

The type of organic solvents used in interfacial polymerization affects the surface property, free volume, and separation performance of the thin-film composite (TFC) polyamide membrane. In this study, TFC polyamide membrane was fabricated through interfacial polymerization between diethylenetriamine (DETA) and trimesoyl chloride (TMC). Four types of organic solvent were explored in the preparation of pervaporation membrane. These are tetralin, toluene, hexane, and isopentane. The solubility parameter distance between organic solvents and DETA follows in increasing order: tetralin (17.07 MPa1/2) < toluene (17.31 MPa1/2) < hexane (19.86 MPa1/2) < isopentane (20.43 MPa1/2). Same trend was also observed between the organic solvents and DETA. The larger the solubility parameter distance, the denser and thicker the polyamide. Consequently, field emission scanning electron microscope (FESEM) and positron annihilation spectroscopy (PAS) analysis revealed that TFCisopentane had the thickest polyamide layer. It also delivered the highest pervaporation efficiency (permeation flux = 860 ± 71 g m-2 h-1; water concentration in permeate = 99.2 ± 0.8 wt%; pervaporation separation index = 959,760) at dehydration of 90 wt% aqueous ethanol solution. Furthermore, TFCisopentane also exhibited a high separation efficiency in isopropanol and tert-butanol. Therefore, a suitable organic solvent in preparation of TFC membrane through interfacial polymerization enables high pervaporation efficiency.

Stability and pervaporation characteristics of PVA and its blend with PVAm membranes in a ternary feed mixture containing highly reactive epichlorohydrin

In order to find an alternative for classical distillation in the recovery of ECH/IPA from azeotropic ECH/IPA/water (50/30/20 w/w, %) mixtures, a pervaporation process has been applied. Membranes from the crosslinking of poly(vinyl alcohol)/poly(vinyl amine) (PVA/PVAm) were prepared, and then the membrane stability and pervaporation efficiency of the crosslinked PVA/PVAm membranes were studied for highly reactive ECH systems containing a ternary feed mixture. From the Fourier-transform infrared (FT-IR) spectroscopy analysis, it was observed that all of the membranes were chemically stable for 15 days of immersion in a 50 : 30 : 20 ECH/IPA/water (w/w, %) feed mixture at 60 °C. The degree of membrane swelling increased with increasing PVAm content in the membrane composition, water content in the feed composition, and feed temperature, which was attributed to the increase in the number of hydrophilic sites in the membrane. The field-emission scanning electron microscopy (FE-SEM) study revealed that higher PVAm content membranes (PVAm1.0 and PVAm1.5) show polymer phase extraction in ECH/IPA/water (50 : 30 : 20) (w/w, %) at 60 °C in long-term stability tests. The pervaporation dehydration characteristics for all of the membranes with the feed comprising an ECH/IPA/water (50 : 30 : 20 by weight) azeotropic mixture at 30 °C were examined and excellent pervaporation dehydration efficiency was found. Quantitatively, the flux increased from 0.025 to 0.32 kg (m2 h)-1 and the separation factor decreased from 1908 to 60 with increasing PVAm content in the blended membrane.

Novel green PVA-fullerenol mixed matrix supported membranes for separating water-THF mixtures by pervaporation

This study focuses first on the preparation of mixed matrix supported membranes of polyvinyl alcohol (PVA) and low-hydroxylated fullerenol C₆₀(OH)₁₂ used to create water selective membranes and then on their pervaporation properties for the separation of water-THF mixtures. These novel supported PVA membranes containing nano-carbon particles were prepared to reach high membrane performance for further integration in a dehydration process, such as distillation coupled to pervaporation. The separation of water-THF mixtures was performed with the supported membranes over a wide range of water concentrations in the feed mixture, i.e., from the azeotrope range up to 30 wt%, to evaluate the performance and stability of the thin active layer. SEM was used to visualize the internal morphology of the membrane. The influence of temperature on the transport properties was also investigated. All the membranes were highly water selective and stable up to 30 wt% water in the feed. The best compromise of transport properties was obtained for the C₆₀(OH)₁₂(5%)-PVA supported composite membrane: a permeate enrichment of 99.3 ± 0.3 wt% water and a flux of 0.25 ± 0.02 kg/(m² h) for the separation of a mixture containing 5.7 wt% water and 94.3 wt% tetrahydrofuran (THF) at 30 °C. Considering its water stability, this supported membrane with a dense layer thinner than 2 μm appears promising for use in hybrid industrial processes to upgrade solvents with a smaller environmental footprint than conventional methods.

Development of Synergistic Antimicrobial Coating of p-Aramid Fibers Using Ag Nanoparticles and Glycidyltrimethylammonium Chloride (GTAC) without the Aid of a Cross-Linking Agent

Functional p-aramid fibers that can express antimicrobial activity were produced by simple processing of silver nanoparticles (AgNPs), which are well known as antimicrobial agents, by using glycidyltrimethylammonium chloride (GTAC), a quaternary ammonium salt. P-aramid fibers were treated with GTAC by the pad-dry-cure process and put into an Ag colloid solution for reactions at 40 °C for 90 min to prepare GTAC/AgNPs-treated p-aramid fibers. Through these processes, GTAC was used as a substitute for existing cross-linking agents. The changes in the degree of attachment of AgNPs to the surface of p-aramid fibers were determined using a scanning electron microscope according to parameters such as GTAC concentration, Ag colloid concentration, and reaction temperature. Through this study, the following results were obtained: (i) The tensile strength of AgNPs/GTAC-treated p-aramid fibers was found to be about 80% of that of untreated p-aramid fibers; (ii) Thermogravimetric analysis showed that the thermal stability of p-aramid fibers did not change much after GTAC/AgNPs treatment and (iii) Antimicrobial activity analysis showed that AgNPs/GTAC-treated p-aramid fibers exhibited superior antibacterial properties compared to untreated p-aramid fibers, which may or may not be the effect of GTAC or AgNPs, or both.

Polyurethane membrane with a cyclodextrin-modified carbon nanotube for pervaporation of phenol/water mixture

Polyurethane (PU) membrane has great potential in pervaporation recovery of phenol from water. In order to improve the permeability of the membrane, cyclodextrin was attached onto carboxylic and hydroxylate carbon nanotubes (CNTs) by physical and chemical methods, with which modified CNTs/PU membranes were prepared. The results showed that the addition of modified CNTs greatly increases the permeability and comprehensive performance of PU membranes in the pervaporation separation of a phenol/water mixture. With 0.5% phenol content in feed at 80°C, the flux and pervaporation separation index of blank PU are 6.10 and 324 kg·μm·m−2·h−1, while those of chemically modified carboxylic CNTs/PU membranes are 156.1 and 655.8 kg·μm·m−2·h−1, respectively.

Development of composite anion-exchange membranes using poly(vinyl alcohol) and silica precursor for pervaporation separation of water–isopropanol mixtures

Composite anion-exchange membranes (AEMs) were prepared using sol–gel techniques with poly(vinyl alcohol) and anion-exchange silica precursor (AESP). Among the composite AEMs, the membrane containing 4 mass% of AESP (M-4) exhibited the excellent pervaporation performance.