Transformation between flocs and aggregates in the conditioned sludge suspensions during a rotational test using a torque rheometer

Floccky tester is a typical torque rheometer used to study flocculants and flocculation characteristics of wastewater sludges. This study presents the variations in rheological, geometric characteristics of conditioned anaerobic digested sludge (ADS) to analyze the transformation between flocs and aggregates during a rotational test with a floccky rheometer. The results revealed that the network strength and resistance to shear reach their maximum values at the optimum dose of polymer zetag7557 on the basis of the area under torque-time curves of ADS. Large aggregates, even big sludge lumps, were observed as soon as the optimum polymer dose was injected into the ADS suspensions, and they continued to grow in average size as the shear duration was prolonged. Afterwards, these aggregates broke into smaller ones or were directly transformed into smaller and smaller flocs with the extension of shear application. The corresponding torque values in the torque-time curve showed similar behavior to the above variations. During the above process, the strongest network formed in conditioned ADS suspensions in which large aggregates were generated, while the ADS suspension with the largest single aggregate or the highest average size of aggregates/flocs did not assure the strongest network. The climax of fractal dimensions for conditioned ADS flocs were not coincident with that of the peak height in the torque-time curves for these ADS suspensions.     

Life cycle of buildings,demolition and recycling potential: A case study in Turin,Italy

One of the most challenging issues presently facing policymakers and public administrators in Italy concerns what to do with waste materials from building dismantling activities and to understand whether, and to what extent, the ever-increasing quantity of demolition waste can replace virgin materials. The paper presents the results from a research programme that was focused on the life cycle assessment (LCA) of a residential building, located in Turin, which was demolished in 2004 by controlled blasting. A detailed LCA model was set-up, based on field measured data from an urban area under demolition and re-design, paying attention to the end-of-life phase and supplying actual data on demolition and rubble recycling. The results have demonstrated that, while building waste recycling is economically feasible and profitable, it is also sustainable from the energetic and environmental point of view. Compared to the environmental burdens associated with the materials embodied in the building shell, the recycling potential is 29% and 18% in terms of life cycle energy and greenhouse emissions, respectively. The recycling potential of the main building materials was made available in order to address future demolition projects and supply basic knowledge in the design for dismantling field.     

Contribution of H-aggregated dye molecules in photocurrent generation of solid-state TiO2|pyrogallol red|CuI solar cell

Excited H-aggregated pyrogallor red molecules are found to be injecting electrons into the conduction band of TiO₂ and holes into the valance band of CuI in solid-state TiO₂|pyrogallor red|CuI cell. Pore filling of titania films by CuI is one of the key parameters controlling the performance of this type of cells. Effect of ligand attached to crystal growth inhibitor on the photocurrent and its dependence with the concentration of crystal growth inhibitor are studied.     

Three-Dimensional Discrete Element Models for Asphalt Mixtures

The main objective of this paper is to develop three-dimensional (3D) microstructure-based discrete element models of asphalt mixtures to study the dynamic modulus from the stress-strain response under compressive loads. The 3D microstructure of the asphalt mixture was obtained from a number of two-dimensional (2D) images. In the 2D discrete element model, the aggregate and mastic were simulated with the captured aggregate and mastic images. The 3D models were reconstructed with a number of 2D models. This stress-strain response of the 3D model was computed under the loading cycles. The stress-strain response was used to predict the asphalt mixture’s stiffness (modulus) by using the aggregate and mastic stiffness. The moduli of the 3D models were compared with the experimental measurements. It was found that the 3D discrete element models were able to predict the mixture moduli across a range of temperatures and loading frequencies. The 3D model prediction was found to be better than that of the 2D model. In addition, the effects of different air void percentages and aggregate moduli to the mixture moduli were investigated and discussed.     

Characterization and microstructure of films made from mucilage of Salvia hispanica and whey protein concentrate

Microstructural, physical and functional properties of thin films (90–110 μm) made from blends of the mucilage of Salvia hispanica (MC) and whey protein concentrate (WPC) were studied. Two proportions of MC:WPC were used (1:3; 1:4) at pH 7 and 10 in distilled water using glycerol as plasticizer. The effects of MC:WPC ratio and pH on colour, solubility, water vapor permeability, mechanical properties and microstructure were investigated. Transmission and scanning electron microscopy were used to investigate the microstructure of aggregates and films. Films produced at pH 10 and MC:WPC ratio of 1:3 has superior mechanical properties than the other films, with higher resistance and flexibility. Also, films produced at pH 10 demonstrated better water vapour barrier (0.620 ± 0.08 g mm/kPa h m²) than films at pH 7. The pH and higher proportion of polysaccharide had a positive influence on mechanical and barrier properties achieving the highest value at pH 10 and higher proportion of polysaccharide.     

Physicochemical properties and thermal stability of Lep w 1, the major allergen of whiff

Whiff (Lepidorhombus whiffiagonis) is a fish frequently consumed in Spain. Lep w 1, its major allergen, is a calcium‐binding β‐parvalbumin. The resistance of Lep w 1 to heat denaturation and to digestion were studied by circular dichroism spectroscopy and by in vitro gastric digestion systems. Purified Lep w 1 was thermally stable up to 65°C at neutral pH. Calcium depletion resulted in a change of its structure as determined by circular dichroism spectroscopy. A partial loss of structure was also observed at acidic pH; however, the allergen retained its full IgE‐binding ability. The partially denatured Lep w 1 was easily digested by pepsin within 2 min. Further, the IgE reactivity of proteins extracted from cooked fish and their stability to proteolysis were analyzed. The extract revealed a higher number of IgE reactive bands than an extract from uncooked fish. IgE binding to these proteins could not be inhibited by an extract from uncooked fish. In contrast to a raw fish extract, the cooked extract showed higher resistance to pepsinolysis. The stability of Lep w 1 to thermal denaturation and digestion explains the high allergenicity of whiff.     

Extraction of cadmium by TODGA–dodecane and TBP–dodecane: A comparative study by MD simulation

Molecular dynamics (MD) simulation of [Cd(II)] along with nitrate ions and water in dodecane was carried out for different nitric acid concentrations. The extraction process using N,N,N’,N’-tetraoctyldiglycolamide (TODGA) and tributyl phosphate (TBP), in biphasic systems, is also simulated at three nitric acid concentrations. In the TBP-based system, the formation of a third phase was observed at 3 M nitric acid concentration. Cd(II) ions form reverse micelles-like clusters with TODGA as an extractant in dodecane. The mass percentage of TODGA in these clusters decreases with increase in the acid concentration while increasing the size of the aggregates at the same time.     

Insight into nitric acid extraction and aggregation of N,N, N’, N’-Tetraoctyl diglycolamide (TODGA) in organic solutions by molecular dynamics simulation

The molecular dynamics (MD) simulation of TODGA in n-dodecane shows formation of nanostructures of TODGA aggregates with nitric acid and water. These aggregates are dispersed in dodecane phase or form well defined reverse micelles grown sufficient in size depending on the acid concentration. With increasing nitric acid concentration, aggregation number of TODGA in reverse micelles also increases which, however, is independent of TODGA concentration. Aggregation number rises from 2 to 8 in presence of 0–3.5 M nitric acid in corresponding aqueous phase. The formation of the aggregates explains remarkable acid co-extraction from aqueous phase to organic dodecane phase by TODGA.     

Enhanced power conversion efficiency in dye-sensitized solar cells with TiO2 aggregates/nanocrystallites mixed photoelectrodes

Photoelectrodes of mixed microsized TiO₂ aggregates and individually dispersed TiO₂ nanocrystallites with different ratios were fabricated and studied for improved power conversion efficiency in dye-sensitized solar cells (DSCs). TiO₂ aggregates/nanocrystallites composites possess several advantages for high performance of DSCs, including the light scattering by the microsized TiO₂ aggregates and the high surface area of nanocrystallites both in aggregates and individually dispersed. A high power conversion efficiency of 7.59% was achieved with mixed TiO₂ aggregates/nanocrystallites photoelectrode using conventional dye N3, without applying anti-reflection coating, back-scattering layer, or chemical treatment. The electron transport properties of DSCs with mixed photoelectrodes were investigated by electrochemical impedance spectra, and the results showed that such a photoelectrode with mixed aggregates and nanocrystallites possess better connectivity for efficient electron transport.     

Localized Aggregation of Diverse Energy Sources for Rural Electrification Using Microgrids

Extension of electrical service to large rural populations in developing nations is a key requirement to realize human development goals set forth by international agencies. This paper presents the case for distributed generation in the form of microgrids, which should be the preferred path towards rural electrification in developing communities and a vital complement to expensive centralized grid expansion. The technical features of frequency and voltage control for distributed generation devices in a microgrid are discussed along with a presentation of their stability attributes. Computer simulation results and experimental results from a laboratory scale microgrid are also presented.