Separation of aqueous salt solution by pervaporation through hybrid organic-inorganic membrane: effect of operating conditions

Hybrid polymer-inorganic membranes were prepared by crosslinking poly(vinyl alcohol) (PVA), maleic acid (MA) and silica via an aqueous sol–gel route. Membrane characterisation results revealed silica nanoparticles (b10 nm) were well dispersed in the polymer matrix and significantly reduced swelling of the membrane. The membranes were tested for pervaporation separation of aqueous salt solution with NaCl concentrations of 0.2–5.0 wt% at temperatures 20–65 °C, feed flowrates 30–150 mL/min and permeate pressures 2–40 Torr. The salt rejection remained high (up to 99.9%) under all operating conditions. A high water flux of 11.7 kg/m2 h could be achieved at a feed temperature of 65 °C and a vacuum of 6 Torr. The effect of operating conditions on water flux is discussed in relation to diffusion coefficients of water and fundamental transport mechanism through the membrane. The activation energy for water permeation was found to vary from 23.8 to 20.1 kJ/kmol when the salt concentration in the feed was increased from 0.2 to 5.0 wt%

Janus hollow fibre membranes with intrusion anchored structure for robust desalination and leachate treatment in direct contact membrane distillation

High-performance Janus membranes have been intriguing for membrane distillation due to its distinctive features for improving fouling and wetting resistance. However, long-term structural stability remains challenging owing to delamination caused by the opposite affinity between the two different kinds of materials. Herein, a physically-anchored hydrophilic layer containing graphene oxide (GO)/poly(vinyl alcohol) (PVA)/sulfosuccinic acid (SSA) i.e., GOSP layer was formed on the surface of a microporous polypropylene (PP) hollow fibre membrane. Meanwhile, the nanostructure of the GOSP layer could be tuned from 2-dimensional lamellar to 3-dimensional mixed matrix, exhibiting various water transport properties. As a result, the fabricated Janus membrane with the partially intruded pore channels exhibited superior antiwetting and antifouling performance for desalination and wastewater treatment in the direct contact membrane distillation process. For surfactant containing saline water, the GOSP/PP Janus membrane with optimised PVA/GO ratio possessed noticeably enhanced anti-wetting property compared to pristine PP membrane. In particular for leachate treatment, the GOSP/PP membrane produced high quality permeate with <1 mg/L ions and 10 mg/L total organics and maintained stable water flux while the leachate was concentrated by 5 times (80 % water recovery), providing great potential for using membrane distillation towards zero liquid discharge

Synthesis and characterization of hybrid organic-inorganic materials based on sulphonated polyamideimide and silica

The preparation of hybrid organic–inorganic membrane materials based on a sulphonated polyamideimide resin and silica filler has been studied. The method allows the sol–gel process to proceed in the presence of a high molecular weight polyamideimide, resulting in well dispersed silica nanoparticles (<50 nm) within the polymer matrix with chemical bonding between the organic and inorganic phases. Tetraethoxysilane (TEOS) was used as the silica precursor and the organosilicate networks were bonded to the polymer matrix via a coupling agent aminopropyltriethoxysilane (APTrEOS). The structure and properties of these hybrid materials were characterized via a range of techniques including FTIR, TGA, DSC, SEM and contact angle analysis. It was found that the compatibility between organic and inorganic phases has been greatly enhanced by the incorporation of APTrEOS. The thermal stability and hydrophilic properties of hybrid materials have also been significantly improved

A mini review on antiwetting studies in membrane distillation for textile wastewater treatment

The textile industry is an important contributor to the growth of the global economy. However, a huge quantity of wastewater is generated as a by-product during textile manufacturing, which hinders the ongoing development of textile industry in terms of environmental sustainability. Membrane distillation (MD), which is driven by thermal-induced vapor pressure difference, is being considered as an emerging economically viable technology to treat the textile wastewater for water reuse. So far, massive efforts have been put into new membrane material developments and modifications of the membrane surface. However, membrane wetting, direct feed solution transport through membrane pores leading to the failure of separation, remains as one of the main challenges for the success and potential commercialization of this separation process as textile wastewater contains membrane wetting inducing surfactants. Herein, this review presents current progress on the MD process for textile wastewater treatment with particular focuses on the fundamentals of membrane wetting, types of membranes applied as well as the fabrication or modification of membranes for anti-wetting properties. This article aims at providing insights in membrane design to enhance the MD separation performance towards commercial application of textile wastewater treatment

Fabrication of high performance TFN membrane containing NH2-SWCNTs via interfacial regulation

A high-flux thin film nanocomposite (TFN) nanofiltration (NF) membrane for low pressure operation (3.5 bar) was fabricated by blending purified amino-functionalized single-walled carbon nanotubes (NH(2)-SWCNTs) with piperazine (PIP) as aqueous phase monomers through interfacial polymerization (IP). The surface properties and structures of the polyamide (PA) active layer were suitably tailored by introducing different amounts of NH(2)-SWCNTs into the PA layer. It was found that the homogeneous incorporation of NH(2)-SWCNTs facilitated a more integral PA layer along with improved roughness, hydrophilicity, and surface charge of the modified membranes, which could be validated by membrane characterisation including SEM, AFM, ATR-FTIR, XPS, zeta potential and water contact angle measurements. Based on cross-flow NF tests, the optimized ultra-thin NH(2)-SWCNT-TFN membranes with 0.002 wt% of NH(2)-SWCNTs exhibited outstanding water permeability of up to 17.8 L m(−2) h(−1) bar(−1), 71.1% higher than that of the pristine membrane, along with high MgSO(4) rejection of 91.0% and Na(2)SO(4) rejection of 96.34%. Meanwhile, NH(2)-SWCNT-TFN membranes also showed excellent long-term stability and antifouling ability. This work demonstrates a facile strategy to fabricate a scalable, low-pressure and ultra-thin TFN membrane with excellent performance