G. Arthanareeswaran

Enhancement of antibacterial properties of silver nanoparticles-ceftriaxone conjugate through Mukia maderaspatana leaf extract mediated synthesis.

Green synthesis of nanoparticles with low range of toxicity and conjugation to antibiotics has become an attractive area of research for several biomedical applications. Nanoconjugates exhibited notable increase in biological activity compared to free antibiotic molecules. With this perception, we report the biosynthesis of silver nanoparticles using aqueous extract of leaves of Mukia maderaspatana and subsequent conjugation of the silver nanoparticles to antibiotic ceftriaxone. The leaves of this plant are known to be a rich source of phenolic compounds with high antioxidant activity that are used as reducing agents. The size, morphology, crystallinity, composition of the synthesized silver nanoparticles and conjugation of ceftriaxone to silver nanoparticles were studied using analytical techniques. The activity of the conjugates against Bacillus subtilis (MTCC 1790), Klebsiella pneumoniae (MTCC 3384), Staphylococcus aureus (ATCC 25923), and Salmonella typhi (MTCC 3224) was compared to ceftriaxone and unconjugated nanoparticles using disc diffusion method. The effect of silver nanoparticles on the reduction of biofilms of Pseudomonas fluorescens (MTCC 6732) was determined by micro plate assay method. The antioxidant activities of extract, silver nitrate, silver nanoparticles, ceftriaxone and conjugates of nanoparticles were evaluated by radical scavenging 1, 1- diphenyl-2-picrylhydrazyl test. Ultraviolet visible spectroscopy and Fourier transform infrared spectroscopy confirmed the formation of metallic silver nanoparticles and conjugation to ceftriaxone. Atomic force microscopy, transmission electron microscopy and particle size analysis showed that the formed particles were of spherical morphology with appreciable nanosize and the conjugation was confirmed by slight increase in surface roughness. The results thus showed that the conjugation of ceftriaxone with silver nanoparticles has better antioxidant and antimicrobial effects than ceftriaxone and unconjugated nanoparticles. It can be suggested that M. maderaspatana mediated nanoparticle-ceftriaxone conjugate can be used effectively in the production of potential antioxidant and antimicrobial agents. The present study offers a significant overview to the development of novel antimicrobial nanoparticles.

Studies on Cellulose Acetate/Low Cyclic Dimmer Polysulfone Blend Ultrafiltration Membranes and their Applications

Abstract Flat sheet ultrafiltration membranes from cellulose acetate (CA)/low cyclic dimer polysulfone (LCD PSf) were prepared by a phase inversion method. N, N′‐Dimethyl formamide and different molecular weight of polyethylene glycol (PEG 200, PEG 400, and PEG 600) were used as solvent and pore‐forming additive, respectively. The membranes were characterized in terms of pure water flux, water content, porosity, membrane hydraulic resistance, and morphology. The pure water flux was found to reach the highest value of 181.82 Lm−2h−1 at 5 wt.% PEG of 600 molecular weight and 10 wt.% LCD PSf content in the blended solution for membrane preparation. SEM micrographs indicated that the addition of PEG into the CA/LCD PSf solution changes the inner structure of the membrane. The influence of filtration time and applied pressure on membrane permeability was examined by copper/polyethylenimine complex rejection studies. With increase in filtration time, the rejection of the copper/polyethylenimine complex decreased and the results were discussed.

Functionalized titanate nanotube–polyetherimide nanocomposite membrane for improved salt rejection under low pressure nanofiltration

Functionalized titanate nanotubes were prepared using a facile and eco-friendly method. Nanofiltration membranes were fabricated via a simple phase inversion method. The neat and mixed matrix membrane (MMMs) was prepared using PEI as a polymeric material and nanomaterials such as TiO2 particles (TP), as-synthesized hydrogen trititanate nanotubes (pTNT), N-doped TiO2NT (N-TNT) and Cu-doped H2Ti3O7NT (Cu-TNT) served as additives. The crystal phase characterization revealed the anatase phase for TP, trititanate phase for pTNT, anatase-rutile mixed phase for N-TNT, Cu-TNT materials and similar observations were found with the MMMs. The morphology analysis of the neat PEI membrane exhibited a denser top layer and the beneath part of the membrane is tighter. Different from the neat PEI membrane nanocomposites of MMMs showed finger-like macrovoids towards the bottom of the membrane. The water uptake and hydrophilic character of the membranes are found in the following order: neat PEI > PEI/TP > PEI/pTNT > PEI/N-TNT > PEI/Cu-TNT. Interestingly, the salt rejection performance of monovalent (NaCl) and divalent (K2SO4 and CaCl2) ions in the single salt mixture were found to increase in the same order. The salt rejection performance of PEI/Cu-TNT was found in the decreasing order: K2SO4 (80%) < NaCl (75%) < CaCl2 (45%). The high performance of PEI/Cu-TNT in salt rejection and antifouling properties is ascribed to the tubular morphology, and the copper dopant results in the high hydrophilic character of the MMMs.

Treatment of laundry wastewater using polyethersulfone/polyvinylpyrollidone ultrafiltration membranes

In this study, laundry wastewater filtration was studied using hydrophilic polyvinylpyrollidone (PVP) modified polyethersulfone (PES) ultrafiltration membranes. The performances of PES/PVP membranes were assessed using commercial PES membrane with 10kDa in ultrafiltration. Operating parameters The influence of transmembrane pressure (TMP) and stirring speed on laundry wastewater flux was investigated. A higher permeate flux of 55.2L/m(2)h was obtained for modified PES membrane with high concentration of PVP at TMP of 500kPa and 750rpm of stirring speed. The separation efficiencies of membranes were also studied with respect to chemical oxygen demand (COD), total dissolved solids (TDS), turbidity and conductivity. Results showed that PES membrane with 10% of PVP had higher permeate flux, flux recovery and less fouling when compared with other membranes. Higher COD and TDS rejection of 88% and 82% were also observed for modified membranes due to the improved surface property of membranes. This indicated that modified PES membranes are suitable for the treatment of surfactant, detergent and oil from laundry wastewater.

PVDF mixed matrix nano-filtration membranes integrated with 1D-PANI/TiO2 NFs for oil–water emulsion separation

The treatment of directly discharged oily waste water is difficult because of colloidal stability and the deformable nature of emulsified oil. In this work, one dimensional (1D) PANI/TiO2 nanofibers (NFs) were incorporated into polyvinylidene fluoride (PVDF) Mixed Matrix Membranes (MMMs) for the removal of oil and water droplets from oily waste water. The size of the 1D PANI/TiO2 (polyaniline/titanium dioxide) NFs ranged between 60 to 75 nm, as identified using transmission electron microscopy (TEM). Atomic force microscopy (AFM) analysis also revealed the significant decrease in the surface roughness of the membranes from 186 to 36 nm following the addition of 1D PANI/TiO2 NFs. Due to the hydrophilic property of the 1D PANI/TiO2 NFs, the contact angle, pure water flux and antifouling properties were increased for 1D PANI/TiO2 NF MMMs compared to the neat PVDF membrane. The pure water flux increased from 80 to 132 L m−2 h−1, which clearly indicates the impact of addition of the 1D PANI/TiO2 NFs. Among the MMMs, PT-4 exhibited the maximum oil rejection of 99% at a 5 bar operating pressure. Hence, the incorporation of PANI/TiO2 NFs in MMMs is proposed to enhance the oil rejection and fouling resistance of MMMs.

Zero-valent iron impregnated cellulose acetate mixed matrix membranes for the treatment of textile industry effluent

Novel green synthesized zero valent iron (ZVI) nanoparticles of distinct mass fractions of 0.5, 1.5 and 2.5 wt% are blended with cellulose acetate (CA) to prepare CA/ZVI mixed matrix membranes (MMMs). The thermal stability and roughness were improved by increasing the mass fraction of ZVI in CA. The morphology of the prepared CA/ZVI membranes has been studied using transmission electron microscopy (TEM). Pure water permeability (PWP) is increased when adding 0.5 wt% of ZVI nanoparticles. When 2.5 wt% is added, PWP decreased due to the aggregation of ZVI nanoparticles in the CA polymer matrix. The adsorption capacity of ZVI nanoparticles on the CA/ZVI membrane during polymer enhanced ultrafiltration of textile effluent is also investigated. The equilibrium adsorption isotherms are well fitted with the Freundlich model, implying the influence of active adsorptive sites of the ZVI nanoparticles.

Effective removal of humic acid using xanthan gum incorporated polyethersulfone membranes

In this study, xanthan gum (XA) was used as a hydrophilic biopolymer additive for the modification of polyethersulfone (PES) membrane to removal of humic acid (HA). The membranes are prepared using phase inversion technique and the concentration of XA was varied from 0.5 to 1.5wt%. The prepared membranes are characterized as a function of hydrophilicity, equilibrium water content (EWC), porosity studies and functional group analysis. Membrane surface and cross-sectional morphology was studied using scanning electron microscope. The lower contact angle value 64.2° was exhibited, when 1.5wt% of XA incorporated in PES membrane and this ensures that increase of hydrophilicity in pristine PES membrane. Further, higher water permeability (PWP) of 68.9(-9)m/skPa was observed for 1.5wt% of XA/PES membrane. The effect of pH on HA removal was studied for neat PES and XA/PES membranes. The rejection performance of XA incorporated in PES membranes were compared with commercial available PES membrane.

Performance enhancement of polysulfone ultrafiltration membrane by blending with polyurethane hydrophilic polymer

Abstract The aim of this work was to study the effect of two solvents such as N,N′-dimethylformamide (DMF) and dimethylacetamide (DMAc) used in the production of polysulfone (PSf) and polyurethane (PU) blend ultrafiltration membranes, influence permeability and selectivity. PSf/PU membranes were prepared by the phase inversion method using polymer concentrations of 100/0, 20/80 and 0/100 wt%. Permeation performance of the prepared membranes was evaluated in terms of pure water flux, water content and hydraulic resistance. It was found that the membrane composed of 20/80 wt% of PSf/PU in the presence of DMAc showed a water flux of 60.5 l m-2h-1 under transmembrane pressure of 345 kPa, and the water flux of 23.5 l m-2h-1 for 20/80 wt% of PSf/PU in the presence of DMF. With increasing the polarity of DMAc in the casting solution, an increase in porous layer thickness was observed, and then a good water flux of membranes can be obtained. It was found that the polar solvent caused the rapidly demixing of casting solution in coagulation bath and formed porous asymmetric membranes with defective skin layer. The permeation rates of proteins were measured with different molecular weights of the proteins.

Influence of bentonite in polymer membranes for effective treatment of car wash effluent to protect the ecosystem.

In this study, modified polyethersulfone (PES) and cellulose acetate (CA) membranes were used in the treatment of car wash effluent using ultrafiltration. Hydrophilic sulfonated poly ether ether ketone (SPEEK) and bentonite as nanoclay were used as additives for the PES and CA membrane modification. Performances of modified membranes were compared with commercial PES membrane with 10kDa molecular weight cut off (MWCO). The influencing parameters like stirrer speed (250-750rpm) and transmembrane pressure (100-600kPa) (TMP) were varied and their effects were studied as a function of flux. In the treatment of car wash effluent, a higher permeate flux of 52.3L/m(2)h was obtained for modified CA membrane at TMP of 400kPa and stirrer speed of 750rpm. In comparison with modified PES membrane and commercial PES membrane, modified CA membranes showed better performance in terms of flux and flux recovery ratio. The highest COD removal (60%) was obtained for modified CA membrane and a lowest COD removal (47%) was observed for commercial PES membrane. The modified membranes were better at removing COD, turbidity and maintained more stable flux than commercial PES membrane, suggesting they will provide better economic performance in car wash effluent reclamation.

Effects of in situ and ex situ formations of silica nanoparticles on polyethersulfone membranes

This study deals with the observed changes in the structure and performance of polyethersulfone (PES) membranes due to in situ formation and ex situ addition of silica particles (SiO2). Hydrolysis and condensation of tetraethyl orthosilicate (TEOS) inside the PES polymer matrix and the reaction of TEOS with ammonium hydroxide were chosen to form in situ and ex situ SiO2 formations, respectively. The resultant structure confirmed by X-ray diffraction for the composite PES membranes showed the retention of the amorphous nature even after the addition of SiO2. The FTIR study revealed the functional groups corresponding to silica networks with enhanced OH signatures on the surface of the composite membranes. Field emission scanning electron microscopic images showed the variation in the surface and cross-sectional structures for the pure and composite membranes. Considerable reduction in the thickness of the skin, difference in the pore structure and ‘finger-like’ cross-sectional morphology with the presence of SiO2 was observed in PES membranes. Both SiO2/PES composite membranes were showed a minor change in their glass transition temperature (Tg). The ex situ methodically formed composite membrane displayed an increase in the pure water flux and decrease in bovine serum albumin rejection as compared to in situ and pure PES membranes. These kinds of composite membranes can be utilized for water treatment applications demanding higher water flux.