A. Nagendran

Separation of macromolecular proteins and rejection of toxic heavy metal ions by PEI/cSMM blend UF membranes

The charged surface modifying macromolecule (cSMM) was blended into the casting solution of poly(ether imide) (PEI) to prepare surface modified ultrafiltration membranes by phase inversion technique. The separation of proteins including bovine serum albumin, egg albumin, pepsin and trypsin was investigated by the fabricated membranes. On increasing cSMM content, solute rejection decreases whereas membrane flux increases. The pore size and surface porosity of the 5 wt% cSMM blend PEI membranes increases to 41.4 Å and 14.8%, respectively. Similarly, the molecular weight cut-off of the membranes ranged from 20 to 45 kDa, depending on the various compositions of the prepared membranes. The toxic heavy metal ions Cu(II), Cr(III), Zn(II) and Pb(II) from aqueous solutions were subjected to rejection by the prepared blended membrane with various concentration of polyethyleneimine (PETIM) as water soluble polymeric ligand. It was found that the rejection behavior of metal ion depends on the PETIM concentration and the stability complexation of metal ion with ligand.

Separation of macromolecular proteins and removal of humic acid by cellulose acetate modified UF membranes.

Surface modifying macromolecules (SMMs) were synthesized with various polyurethane pre polymers end-capped with different groups and blended into the casting solution of cellulose acetate (CA) to prepare surface modified ultra-filtration (UF) membranes for water filtration applications. The surface modification of the CA membranes was confirmed by the FTIR and static contact angle (SCA) measurements. The membranes so prepared had the typical characteristics of UF membranes as confirmed by scanning electron microscopy (SEM). Membrane properties were studied in terms of membrane compaction, percentage water content (%WC), pure water flux (PWF), membrane hydraulic resistance (Rm), molecular weight cut-off (MWCO), average pore size and porosity. The result showed that PWF, %WC, MWCO and pore size increased whereas the Rm decreased by the addition of SMMs. The significant effect of SMMs on the fouling by humic acid (HA) was also observed. It was found that the cSMM-3 membrane, in which SMM was synthesized with diethylene glycol (DEG) and hydroxyl benzene sulfonate (HBS) was blended, had the highest flux recovery ratio FRR (84.6%), as well as the lowest irreversible fouling (15.4%), confirming their improved antifouling properties. Thus, the SMM modified CA membranes had proven, to play an important role in the water treatment by UF.

Preparation, characterization and performance of cellulose acetate ultrafiltration membranes modified by charged surface modifying macromolecule

A charged surface modifying macromolecule (cSMM) was synthesized, characterized by FT-IR spectroscopy and blended into the casting solution of cellulose acetate (CA) to prepare surface modified UF membranes by phase inversion technique. With an increasing cSMM additive content from 1 to 4 wt%, pure water flux (PWF) and water content (WC) were increases whereas the hydraulic resistance decreases. Surface characteristic study reveals that the surface hydrophilicity increased in cSMM modified CA membranes. The pore size and surface porosity of the 4 wt% cSMM blend CA membranes increases to 41.26 Å and 0.015%, respectively. Similarly, the molecular weight cut-off (MWCO) of the membranes ranged from 20 to 45 kDa, depending on the various compositions of the prepared membranes. Lower flux decline rate (47.2%) and higher flux recovery ratio (FRR) (89.0%), exhibited by 4 wt% cSMM blend membranes demonstrated its fouling resistant characteristic compared to pristine CA membrane.

Effect of sulfonated graphene oxide on the performance enhancement of acid–base composite membranes for direct methanol fuel cells

Sulfonated poly(1,4-phenylene ether ether sulfone) (SPEES)/poly(ether imide) (PEI)/sulfonated graphene oxide (SGO) based proton exchange membranes (PEMs) were prepared by a solution casting method. The membranes were characterized for their tensile strength, thermal stability, electrochemical properties and physico-chemical properties using a universal testing machine, thermogravimetric analyzer, impedance spectroscopy and water uptake studies respectively. Compared with SPEES/PEI composite (SP) membranes, the ion exchange capacity, hydrophilicity and water uptake of the SP/SGO membranes were enhanced. Surface morphology of the composite membrane was investigated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM images reveal that the nodule size and surface roughness are increased by the incorporation of SGO. Tensile strength and proton conductivity of the composite membranes increased with increasing SGO content. A maximum conductivity of 8.87 × 10−3 S cm−1 was achieved at 25 °C upon addition of 0.8 wt% of SGO. All the SP/SGO membranes exhibited methanol permeability lower than 3.26 × 10−7 cm2 s−1, which was much lower than that of Nafion 117 (3.41 × 10−6 cm2 s−1). Furthermore, the composite membranes exhibited much higher relative selectivity compared with SP and Nafion 117 membranes. It was found that the SP/SGO-0.8 composite membrane appears to be a good candidate for use in DMFC applications.

SPEES/PEI-based highly selective polymer electrolyte membranes for DMFC application

Polymer composite membranes based on sulfonated poly(phenylene ether ether sulfone) (SPEES) membrane with varying concentrations of poly(ether imide) (PEI) were prepared. The sulfonation of PEES was carried out with concentrated sulfuric acid at 10 °C, and the sulfonation degree was maintained as 70 %. The introduction of PEI into the hydrophilic SPEES matrix provided good chemical stability to the membrane. The water uptake, ion exchange capacity, and proton conductivity decrease with increasing PEI content. Scanning electron microscopy (SEM) indicates that PEI particles are homogeneously dispersed into the composite membrane. Thermogravimetric analysis (TGA) showed that all the composite membranes exhibited good thermal stability. On the other hand, the methanol permeability of the composite membranes gradually decreases from 4.23 × 10−7 cm2 s−1 to 8.84 × 10−8 cm2 s−1, which is lower than that of the Nafion 117 membrane. The relative selectivity of the PEI-incorporated SPEES membranes was higher than that of the Nafion membranes. From the observed results, the prepared SPEES/PEI-15 composite membrane can be considered as apposite polymer electrolyte membranes for the application of direct methanol fuel cells (DMFCs).

Performance studies of PEI/SPEI blend ultra-filtration membranes via surface modification using cSMM additives

Sulfonated poly(ether imide) (SPEI) and charged surface modifying macromolecules (cSMM) were synthesized, characterized and blended into the casting solution of poly (ether imide) (PEI) with different compositions to develop surface modified ultra-filtration (UF) membranes by means of improved hydrophilicity. The membranes were prepared by a phase inversion technique and subjected to characterization experiments such as water permeation tests, equilibrium water content (WC), membrane hydraulic resistance (Rm) and protein rejection. Among others, a blend membrane containing 20 wt% SPEI and 5 wt% cSMM in PEI (called M12) exhibited the highest water permeation (440.6 L m−2 h−1 at 345 kPa), highest WC (86.3%) and lowest Rm (0.7 kPa/L m−2 h−1). The M12 membrane also exhibited the highest fluxes of 364.1 L m−2 h−1 and 230.3 L m−2 h−1 (at 345 kPa) with rejections of 31.3% and 62.1%, respectively, when the feed was aqueous trypsin and bovine serum albumin solution (1000 ppm). The difference in contact angle between the top and bottom surface confirmed surface migration of cSMM to the membrane top surface. SEM, AFM and tensile strength measurement revealed that the surface became more porous and rougher, and the mechanical strength was lowered by the blending of SPEI and addition of cSMM. That the M12 membrane achieved a lower internal fouling of 6% and 3.8% and higher flux recovery ratio (FRR) of 94% and 96.2% after UF of trypsin and bovine serum albumin solution explained its better antifouling properties as compared to a pristine PEI membrane.

Tailored PVDF nanocomposite membranes using exfoliated MoS2 nanosheets for improved permeation and antifouling performance

Exfoliated molybdenum disulfide (E-MoS2) nanosheets were synthesized from bulk MoS2. Poly(vinylidene fluoride) (PVDF) was incorporated into E-MoS2 to yield nanocomposite ultrafiltration (UF) membranes by the phase inversion technique. Various proportions of E-MoS2 (0.1, 0.5 and 0.8 wt%) were prepared and were characterized in terms of permeation and antifouling properties. FT-IR and XRD studies confirmed the presence of E-MoS2 in the membranes. Moreover, SEM and FESEM/EDX analysis of the membranes confirmed the increase in the porosity and presence, respectively, of E-MoS2. Atomic force microscopy (AFM) images confirmed that the membrane with 0.5 wt% E-MoS2 exhibited a uniform surface structure with (Ra = 35 nm), compared to the pure PVDF membrane (Ra = 37.6 nm). In addition, the membrane with 0.5 wt% E-MoS2, exhibited higher pure water flux (PWF) (105.1 L m−1 h−1), water content (73.7%), porosity (12.24%), bovine serum albumin (BSA) solute rejection (92.3%), least mechanical stability (1.13 MPa), hydraulic resistance (7.44 kPa L−1 m−2 h−1) and contact angle (72.8°). From all these, it is evident that the overall PVDF membrane performance was enhanced by the E-MoS2 addition, and the membrane with 0.5 wt% E-MoS2 outperformed the other counterparts due to its versatile characteristics and superior potential in the water treatment.

Fabrication of cellulose acetate nanocomposite membranes using 2D layered nanomaterials for macromolecular separation

Cellulose acetate (CA) nanocomposite ultrafiltration (UF) membranes were fabricated using 2D layered nanosheets such as graphene oxide (GO) and exfoliated molybdenum disulfide (E-MoS2) and effectively used for the removal of macromolecular protein. The GO and E-MoS2 nanosheets were prepared and characterized by FT-IR and XRD respectively. GO and E-MoS2 (0.5wt.%) were blended individually with CA. The assenting changes generated by the incorporation of GO and E-MoS2 in terms of surface hydrophilicity of the nanocomposite membrane were analyzed by pure water flux (PWF) and contact angle measurement. The influence of 2D nanosheets on the morphology of CA are studied by scanning electron microscopy (SEM). Mechanical strength and hydraulic resistance of the nanocomposite membranes were found to be improved compared to bare CA membrane. The separation and antifouling performance of the nanocomposite membranes were studied using macromolecular bovine serum albumin (BSA). From the results, it was observed that a CA/GO-0.5 membrane exhibited the highest PWF (125.4±1.7Lm-2h-1), water content (70.6±1.2%), porosity (34.6±1.7%), flux recovery ratio (FRR) (88.8±1.6%) and lowest contact angle (63.9±2.5°), hydraulic resistance (4.3±0.67kPa/Lm-2h -1) than pure CA and CA/E-MoS2-0.5 membranes. CA/GO-0.5 membrane displayed superior UF and antifouling performance due to the greater affinity of GO nanoparticles towards water.

Custom-made PEI/exfoliated-MoS 2 nanocomposite ultrafiltration membranes for separation of bovine serum albumin and humic acid

Herein, we report the effect of the exfoliated molybdenum disulfide (eMoS2) nanosheets in improving the permeability and anti-fouling properties of the PEI ultra-filtration (UF) membrane using bovine serum albumin (BSA) and humic acid (HA) as model fouling agents. The PEI/eMoS2 nanocomposite membranes were prepared via phase inversion method using three different eMoS2 concentrations (0.5, 1 and 2wt%) designated as PEI-0.5, PEI-1 and PEI-2, respectively. Fourier transform infra-red spectroscopy employed to probe the surface functionalities on the membranes. Contact angle measurement, pure water flux, swelling rate and solute rejection studies confirmed the improved hydrophilicity of the PEI/eMoS2 nanocomposite membranes than the individual entities. Flux recovery ratio (FRR), reversible and irreversible fouling results evidenced the improved fouling resistance of PEI/eMoS2 modified membranes than the individual counterparts. SEM results evidenced that the nanoscale eMoS2 significantly altered the membrane morphology by causing increased porosity and larger macrovoids formation on the surface as well as in the bulk of the membrane. PEI-1 membrane showed an increased pure water flux (52.54Lm-2h-1) and water content (74.8%) whereas lesser contact angle (69.2°) and hydraulic resistance (1.85kPa/Lm-2h-1). Resistance to fouling performance of PEI-1 membrane was evident from the FRR values of 95.3 and 90.2% and rejection values of 94.5 and 92.4% for BSA and HA respectively. PEI-2 membrane agglomerates with eMoS2 and hindered the membrane permeability by blocking the macrovoids in the bulk which restricted the permeation and fouling resistance of the membrane. Amongst various nanocomposite membranes investigated, the PEI-1 membrane exhibited better hydrophilicity and fouling resistance properties due to the availability of the favorable surface and bulk characteristics.

Biopolymer Composites in Fuel Cells

Abstract The wide use of fossil fuels, which resulted in severe pollutant emissions, present a menace to the wellness of mankind. In addition, a steady diminution of world’s limited fossil fuel reserves call for efficient, benign, and sustainable technologies for energy transition and power generation. Fuel cells have been identified as one of the most efficient and promising alternative technologies to traditional power sources due to its lower carbon footprint and greater conversion efficiency. A fuel cell is an energy conversion device that generates DC electrical power by converting the chemical energy of a fuel into electrical energy and heat through catalyzed electrochemical reactions. Fuel cells typically utilize hydrogen as the fuel, and oxygen (or oxygen from the air) as the oxidant. Generally fuel cells are classified based on electrolyte material used, among them polymer electrolyte membranes (PEMs) offer advantages such as high efficiency and high energy density. Nevertheless, most of the present-day polymers that are being presently applied in PEM fuel cell applications are synthetic materials; their biocompatibility and biodegradability are much more limited than those of natural polymers such as cellulose, starch, glycogen, chitin and chitosan, and their derivatives. The utilization of biopolymer for fuel cell technologies is novel and challenging where biological products are usually considered as waste, nonhazardous, and environmentally benign. Especially, the low production cost of the biopolymer is an attractive feature. Hence recently, profusely available biopolymers and their composites have been widely analyzed as materials for membrane electrolytes and electrodes in low to intermediate temperature hydrogen polymer electrolyte fuel cells, direct methanol fuel cells, alkaline fuel cells, and biofuel cells. The chapter provides an overview of applications of novel biopolymers and their composites in fuel cells technology.