Storm water harvesting and reuse in Australia : enhanced sand filtration for the treatment of storm water

This study details the removal of common storm water pollutants along with heavy metals by enhanced sand filtration. Three filtration flow rates were trialled: 5, 10 and 20 m/h. The performance of each filter was rated on the ability to remove turbidity, suspended solids, dissolved solids, phosphorus, nitrogen, lead, copper and Zinc. Conventional sand filter was used as a performance benchmark, and compared with four sand filters that are enhanced with a nylon carpet fibre, polypropylene carpet fibre, Syrian carpet fibre-enhanced and alum sludge-enhanced sand filter. Carpet fibre-enhanced sand filtration was highly effective at filtering simulated storm water and in most cases performing well above the conventional sand filters. The carpet fibre-enhanced sand filters had no drop in flow rates over the 4 h filtration period with following removal rates: up to 90% total suspended solids, 70% zinc, 60% turbidity, 25% phosphorus, 15% nitrogen and 10% total dissolved solids. However, results showed that alum sludge-enhanced sand filter performed the highest, with removal rates up to 100% for total suspended solids, 80% zinc, 90% turbidity, up to 80% phosphorus, up to 40% nitrogen and 3% total dissolved solids. But the flow rates dropped approximately two-thirds of the original flow rates within the first hour. © 2014 © 2014 Balaban Desalination Publications. All rights reserved.

Retention of the original LLC structure in a cross-linked poly(ethylene glycol) diacrylate hydrogel with reinforcement from a silica network

Cross-linked poly(ethylene glycol) diacrylate (PEGDA) hydrogels with uniformly controlled nanoporous structures templated from hexagonal lyotropic liquid crystals (LLC) represent separation membrane materials with potentially high permeability and selectivity due to their high pore density and narrow pore size distribution. However, retaining LLC templated nanostructures is a challenge as the polymer gels are not strong enough to sustain the surface tension during the drying process. In the current study, cross-linked PEGDA gels were reinforced with a silica network synthesized via an in situ sol-gel method, which assists in the retention of the hexagonal LLC structure. The silica precursor does not obstruct the formation of hexagonal phases. After surfactant removal and drying, these hexagonal structures in samples with a certain amount of tetraethoxysilane (TEOS) loading are well retained while the nanostructures are collapsed in samples without silica reinforcement, leading to the hypothesis that the reinforcement provided by the silica network stabilizes the LLC structure. The study examines the conditions necessary for a sufficient and well dispersed silica network in PEGDA gels that contributes to the retention of original LLC structures, which potentially enables broad applications of these gels as biomedical and membrane materials.

Structure-property relationships in nylon 6 nanocomposites based on octaphenyl-, dodecaphenyl-POSS, montmorillonite, and their combinations

Binary and ternary nanocomposites were produced by incorporating, via melt compounding, two types of octa-and dodecaphenyl substituted polyhedral oligomeric silsesquioxanes (POSS), montmorillonite (MMT), and combinations of POSS with MMT into nylon 6. The tensile, flexural, and dynamic thermo-mechanical properties of these materials were characterized and their structure-property relationships discussed. The results show that the losses in ductility and toughness experienced after inclusion of MMT into nylon 6 can be balanced out by co-mixing MMT with the dodecaphenyl- POSS to produce a ternary nanocomposite. This trend however was less pronounced in the ternary MMT/octaphenyl-POSS system. Analysis of the microstructure organization in these materials using XRD and SEM sheds some light on understanding the differences in behavior. Both types of POSS particles mixed alone in nylon 6 were found to be polydisperse (500 nm to a few microns in size) and locally aggregated, yielding materials with similar mechanical performance. The co-mixing of MMT with the octaphenyl- POSS served to break down the POSS crystal aggregates, enhancing their micro-mechanical reinforcing action. On the other hand, the POSS crystals were not affected in the MMT/dodecaphenyl-POSS system, which led to improving their toughening ability.

Mechanical properties of graphene films enhanced by homo-telechelic functionalized polymer fillers via π-π Stacking interactions

© 2015 Elsevier Ltd. All rights reserved. Most researches on graphene/polymer composites are focusing on improving the mechanical and electrical properties of polymers at low graphene content instead of paying attention to constructing graphene's macroscopic structures. In current study the homo-telechelic functionalized polyethylene glycols (FPEGs) were tailored with π-orbital-rich groups (namely phenyl, pyrene and di-pyrene) via esterification reactions, which enhanced the interaction between polyethylene glycol (PEG) molecules and chemical reduced graphene oxide (RGO) sheets. The π-π stacking interactions between graphene sheets and π-orbital-rich groups endowed the composite films with enhanced tensile strength and tunable electrical conductivity. The formation of graphene network structure mediated by the FPEGs fillers via π-π stacking non-covalent interactions should account for the experimental results. The experimental investigations were also complemented with theoretical calculation using a density functional theory. Atomic force microscope (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), thermal gravimetric analysis (TGA), UV-vis and fluorescence spectroscopy were used to monitor the step-wise preparation of graphene composite films.

Development of hybrid composites for automotive applications: effect of addition of SEBS on the morphology, mechanical, viscoelastic, crystallization and thermal degradation properties of PP/PS-xGnP composites

In this article, we report on a simple and cost effective approach for the development of light-weight, super-tough and stiff material for automotive applications. Nanocomposites based on PP/PS blend and exfoliated graphene nanoplatelets (xGnP) were prepared with and without SEBS. Mechanical, crystallization and thermal degradation properties were determined and correlated with phase morphology. The addition of xGnP to PP/PS blend increased the tensile modulus at the expense of toughness. The presence of xGnP increased the enthalpy of crystallization and enthalpy of fusion of PP in the blends, without affecting segmental mobility and thermal stability. Addition of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) improved the toughness of PP/PS blends, but decreased the stiffness. The incorporation of xGnP into this ternary blend generated a super-tough material with improved stiffness and tensile elongation, suitable for automotive applications. It is observed that the presence of SEBS diminished the tendency of agglomeration of xGnP and their unfavorable interactions with thermoplastics, which in turn reduced the internal friction in the matrix.

Hydrogen bonding interactions in poly(ε-caprolactone-dimethyl siloxane-ε-caprolactone)/poly(hydroxyether of bisphenol A) triblock copolymer/homopolymer blends and the effect on crystallization, microphase separation and self-assembly

This study investigated the self-assembled microphase separated morphologies that are obtained in bulk, by the complexation of a semicrystalline poly(ε-caprolactone-dimethyl siloxane-ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer and a homopolymer, poly(hydroxyether of bisphenol A) (PH) in tetrahydrofuran (THF). In these blends, microphase separation takes place due to the disparity in intermolecular interactions; specifically, the homopolymer interacts with PCL blocks through hydrogen bonding interactions. The crystallization, microphase separation and crystalline structures of a triblock copolymer/homopolymer blends were investigated. The phase behavior of the complexes was investigated using small-angle X-ray scattering and transmission electron microscopy. At low PH concentrations, PCL interacts relatively weakly with PH, whereas in complexes containing more than 50 wt% PH, the PCL block interacts significantly with PH, leading to the formation of composition-dependent nanostructures. SAXS and TEM results indicate that the lamellar morphology of neat PCL-PDMS-PCL triblock copolymer changes into disordered structures at 40-60 wt% PH. Spherical microdomains were obtained in the order of 40-50 nm in complexes with 80 wt% PH. At this concentration, the complexes show a completely homogenous phase of PH/PCL, with phase-separated spherical PDMS domains. The formation of these nanostructures and changes in morphology depends on the strength of hydrogen bonding between PH/PCL blocks and also the phase separated PDMS blocks.

High performance PP/SEBS/CNF composites: evaluation of mechanical, thermal degradation, and crystallization properties

Nanocomposites comprising carbon nanofibers (CNF) were prepared and evaluated in terms of morphology, mechanical performance, thermal stability and crystallization properties. It was found that addition of CNF reinforced polypropylene (PP) matrix by marginally increasing the strength and modulus, but at the expense of toughness and ductility. To improve the toughness of the composites, polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) was used. Presence of SEBS remarkably improved the toughness and ductility of the composites. The optimum level of reinforcement was observed at 0.1 wt% of CNF in the composites. Phase morphology studies revealed that at this concentration, CNF were well dispersed in polymer phases and beyond it, agglomeration occurred. PP/SEBS/CNF (0.1 wt%) nanocomposites exhibited good strength, excellent toughness and decent modulus, which make them suitable for cost effective, light-weight, tough and stiff material for engineering applications. It was observed that thermal stability of composites is only marginally improved whereas crystallinity of PP drastically reduced by the addition of CNF.

Dynamic performance of duolayers at the air/water interface. 2. Mechanistic insights from all-atom simulations

The novel duolayer system, comprising a monolayer of ethylene glycol monooctadecyl ether (C18E1) and the water-soluble polymer poly(vinylpyrrolidone) (PVP), has been shown to resist forces such as wind stress to a greater degree than the C18E1 monolayer alone. This paper reports all-atom molecular dynamics simulations comparing the monolayer (C18E1 alone) and duolayer systems under an applied force parallel to the air/water interface. The simulations show that, due to the presence of PVP at the interface, the duolayer film exhibits an increase in chain tilt, ordering, and density, as well as a lower lateral velocity compared to the monolayer. These results provide a molecular rationale for the improved performance of the duolayer system under wind conditions, as well as an atomic-level explanation for the observed efficacy of the duolayer system as an evaporation suppressant, which may serve as a useful guide for future development for thin films where resistance to external perturbation is desirable.

Morphology-properties relationship of gas plasma treated hydrophobic meso-porous membranes and their improved performance for desalination by membrane distillation

The impact on performance of the surface energy and roughness of membrane materials used for direct contact membrane distillation are critical but yet poorly investigated parameters. The capacity to alter the wettability of highly hydrophobic materials such as poly(tetra-fluoro-ethylene) (PTFE) by gas plasma treatments is reported in this paper. An equally important contribution from this investigation arises from illustrating how vaporized material from the treated sample participates after a short while in the composition of the plasma and fundamentally changes the result of surface chemistry processes. The water contact angle across the hydrophobic membranes is generally controlled by varying the plasma gas conditions, such as the plasma power, chamber pressure and irradiation duration. Changes to surface porosity and roughness of the bulk material as well as the surface chemistry, through specific and partial de-fluorination of the surface were detected and systematically studied by Fourier transform infra-red analysis and scanning electron microscopy. It was found that the rupture of fibrils, formed during membrane processing by thermal-stretching, led to the formation of a denser surface composed of nodules similar to these naturally acting as bridging points across the membrane material between fibrils. This structural change has a profound and impart a permanent effect on the permeation across the modified membranes, which was found to be enhanced by up to 10% for long plasma exposures while the selectivity of the membranes was found to remain unaffected by the treatment at a level higher than 99.99%. This is the first time that an investigation demonstrates how the permeation characteristics of these membranes is directly related to data from spectral, morphological and surface charge analyses, which provide new insights on the impact of plasma treatments on both, the surface charge and roughness, of PTFE porous materials.

The role of SEBS in tailoring the interface between the polymer matrix and exfoliated graphene nanoplatelets in hybrid composites

Nanocomposites of polypropylene (PP) and polypropylene/styrene-(ethylene-co-butylene)-styrene triblock copolymer (SEBS) blends with exfoliated graphene nanoplatelets (xGnP) were prepared by melt-mixing method. The incorporation of xGnP increased the stiffness and crystallinity of PP at the expense of toughness and the molecular mobility. The effect of addition of SEBS on the mechanical, viscoelastic, thermal degradation and crystallization properties of PP/xGnP composites was studied. The addition of SEBS into PP transformed the phase structure and distribution of xGnP in the PP matrix. SEM micrographs revealed that SEBS polymer chains formed a coating over the graphene nanoplatelets, which strengthened the interface between the filler and the matrix, and improved the dispersion and distribution of the filler throughout the matrix.

Enhanced homogeneity and interfacial compatibility in melt-extruded cellulose nano-fibers reinforced polyethylene via surface adsorption of poly(ethylene glycol)-block-poly(ethylene) amphiphiles

In this paper, we demonstrate that an amphiphilic block copolymer such as polyethylene glycol-b-polyethylene can be used as both dispersing and interfacial compatibilizing agent for the melt compounding of LLDPE with cellulose nano-fibers. A simple and effective spray drying methodology was first used for the first time for the preparation of a powdered cellulose nano-fibers extrusion feedstock. Surface adsorption of the amphiphilic PEG-b-PE was carried out directly in solution during this process. These various dry cellulosic feedstock were subsequently combined with LLDPE via extrusion to produce a range of nano-composites. The collective outcomes of this research are several folds. Firstly we show that presence of surface adsorbed PEG-b-PE effectively hindered the aggregation of the cellulose nano-fibers during the extrusion, affording clear homogenous materials with minimum aggregation even at the highest loading of cellulose nano-fibers (∼23 vol.%). Secondly, the tailored LLDPE/cellulose interface arising from intra- and inter-molecular hydrogen and Van der Waals bonds yielded significant levels of mechanical improvements in terms of storage and tensile modulus. We believe this study provides a simple technological template to produce high quality and performant polyolefins cellulose-based nano-composites.

Molecular interactions behind the synergistic effect in mixed monolayers of 1-octadecanol and ethylene glycol monooctadecyl ether

Mixed monolayers of 1-octadecanol (C18OH) and ethylene glycol monooctadecyl ether (C18E1) were studied to assess their evaporation suppressing performance. An unexpected increase in performance and stability was found around the 0.5:0.5 bicomponent mixture and has been ascribed to a synergistic effect of the monolayers. Molecular dynamics simulations have attributed this to an additional hydrogen bonding interaction between the monolayer and water, due to the exposed ether oxygen of C18E1 in the mixed system compared to the same ether oxygen in the pure C18E1 system. This interaction is maximized around the 0.5:0.5 ratio due to the particular interfacial geometry associated with this mixture.