1,721,033 research outputs found
Editorial for the special issue on “process intensification techniques for the production of nanoparticles”
Full text linkAccording to ISO/TS 80004, a nanomaterial is defined as the "material with any external dimension in the nanoscale or having internal structure or surface structure in the nanoscale", with nanoscale defined as the "length range approximately from 1 nm to 100 nm" [...]
Circular economy of wastewater streams by means of membrane technologies
No full textIn this Chapter the circular economy possibilities on membranes used for wastewater treatment processes are exploited. Circular economy in this case can be performed on two different aspects of the same technology: on the product streams and on the membrane modules. The first is performed by valorization of the waste stream, that is the stream separating in the membrane module and that is not considered to be the process one. In most cases, this stream correspond to the concentrate, and in the past was always discharged as a waste. The latter one can be achieved by increasing the longevity of the membrane module and, once exhausted, to think about after life applications. In the past, exhausted membrane modules were seen as a solid waste in line with consumables. Achieving circular economy in membrane technology is therefore not a simple task, and requires proper process design to be achieved
Spinning disc reactor to produce nanoparticles. Applications and best operating variables
Full text linkA spinning disc reactor (SDR) is a useful equipment to produce monodisperse nanoparticles with controllable properties, as particle size and particle size distribution. Since the late 90s, this technology has been successfully proven for the reaction and solvent-antisolvent precipitation process. This paper reviews the works on the use of SDR to produce inorganic and organic compounds. Firstly, the more significant works on the subject are presented concerning the produced compound, then the factors influencing the process performances are examined in the light of the results in the literature. Finally, some considerations on the fluid stream's hydrodynamics modelling along the disc surface are attempted
Pre-treatment processes optimization for the purification of olive mill wastewater through a pilot-scale membrane plant
No full textThe reported work deals with the evaluation of two different pre-treatment processes performances for the purification of a real olive mill wastewater. The wastewater was from an oil mill placed in the South of Italy and presents high Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) and phenols concentrations, besides other organic pollutants, an acid pH and brown colour. Therefore, this complex wastewater resulted in low- biodegradable and difficult to be treated by a solely process. To this aim, the present work will evaluate optimal operating parameters of coagulation-flocculation and photocatalysis pre-treatments to achieve suitable physical-chemical properties of the effluent, before the membrane treatment in a pilot-scale plant. In detail, the wastewater was firstly treated with an organic coagulant (chitosan) and then a photocatalytic step follows before the more efficient integrated membrane process. After the photocatalytic process, the COD, TOC and Phenols concentrations decreased to up 42 %, 38 % and 36 %, respectively, in comparison with the initial values. Subsequently, a series of four separation processes (ultrafiltration, nanofiltration and reverse osmosis) was performed and almost the total initial COD, TOC and phenols concentrations were removed
A study on the relationship between the boundary flux parameters and membrane process requirements
Full text linkThe boundary flux concept permits to describe the fouling behaviour of membrane systems as a function of the operating time. The method relies on a set of equations that is possible to integrate in time, thus permitting to evaluate the separation process outcome and performances. This study focuses on the relationship between the membrane area requirements and specific parameters of the boundary flux concept on different membrane systems characterized by different waste feed streams and operating conditions. The target of the analysis was to identify which parameters of the boundary flux equations are the most influent one on the membrane area requirements. The knowledge of the relevant parameters can strongly assist membrane process designers to minimize the capex of the developed plants. The study was performed on many different systems, available in literature, and at different operating conditions. In order to avoid the triggering of irreversible fouling, the operation must be performed in sub-boundary operating conditions, and as a consequence, the condition of the permeate flux Jp equal to the boundary flux Jb must be met at the end of operation. Summarizing briefly the findings, it was possible to observe that the membrane area requirements are minimized for higher pure water membrane permeability values (w) for recoveries up to 75% Ymax, but then, in the range up to 90% Ymax, to achieve the same target, it appears to be more important to have higher Jb values. In other words, in those systems characterized by VRF (volume recovery factor) less than 4, high membrane permeabilities appears advantageous for the choice, even in presence of some extent of fouling. This appears not to be the case for those systems targeting higher VRF values: in this case, high Jb values must be achieved. Since the value of Jb depends on many parameters, such as T, Re and other physical-chemical characteristics, the minimization of the membrane area requirements requires the proper design of the membrane process, pre-treatment steps and operating conditions choice
Nanocomposites photocatalysis application for the purification of phenols and real olive mill wastewater through a sequential process
Full text linkIn this study, a synthetic phenol solution of water and raw olive mill wastewater (OMW) were considered to achieve purification of the aqueous streams from pollutants. Only OMW was initially submitted to a coagulation/flocculation process, to reduce the turbidity, phenols, and chemical oxygen demand (COD). This first treatment appeared to be mandatory in order to remove solids from wastewater, allowing the successive use of laboratory-made core-shell nanocomposites. In detail, the optimal coagulant concentration, i.e., chitosan, was 500 mg/L, allowing a reduction of the turbidity and the COD value by 90% and 33%, respectively. After this, phenol wastewater was tested for photocatalysis and then OMW was treated by employing the laboratory-made nanocomposites in a photoreactor equipped with visible light sources and using optimal catalyst concentrations, which allowed for an additional 45% reduction of the COD of the OMW. In addition to this, the effect of the operating temperature was investigated on the photocatalytic process, and suitable kinetic models proposed
On the micromixing behavior of a spinning disk reactor for metallic Cu nanoparticles production
Full text linkThe interest in producing copper nanoparticles is high, mainly due to their enhanced properties, a wide range of possible and different applications, and the possibility for their use in the framework of catalysis. The purpose of this study is to synthesize copper nanoparticles by chemical reduction of copper sulfate with L-ascorbic acid and sodium borohydride capable to eliminate free radicals providing an antioxidant environment promoting pure copper nuclei formation. The micromixing conditions necessary for the nanoparticles production are provided by a spinning disk reactor (SDR). Relevant operational parameters, such as the disk speed velocity and the position of the reactant injectors, will lead to different product outcomes. The latter was checked by means of a dynamic light scattering instrument (DLS). At the end, depending on the adopted operating conditions, the SDR was able to produce particles between 16 nm and 39 nm, with a particle size distribution (PSD) characterized by a narrow, monomodal plot. In comparison to the smallest particles obtained in a stirred reactor tank, that is, 132 nm, the obtained results appear to be very promising
On the effect of specific boundary flux parameters on membrane process design
Full text linkThe boundary flux concept permits to describe the fouling behaviour of membrane systems as a function of the operating time. The method relies on a set of equations that is possible to integrate in time, thus permitting to evaluate the separation process outcome and performances. This study focuses on the relationship between the membrane area requirements and specific parameters of the boundary flux concept on different membrane systems characterized by different waste feed streams and operating conditions. The target of the analysis was to identify which parameters of the boundary flux equations are the most influent one on the membrane area requirements. The knowledge of the relevant parameters can strongly assist membrane process designers to minimize the capex of the developed plants. The study was performed on many different systems, available in literature, and at different operating conditions. The adopted procedure was as follows: 1. in a first step, by using infinite membrane area, the maximum recovery value Ymax of a specific membrane separation process was determined. 2. afterwards, the separation target was equally fixed at volume unity of feed (1 m3) produced during time unity (1 h) at three different recovery values, that is Y equal to 50% Ymax, 75% Ymax and 90% Ymax, respectively. The required membrane area below boundary conditions and no irreversible fouling formation was calculated by means of the simulation code, using a Newtonian trial&error procedure
Development of a diafiltration-pervaporation process for beer dealcoholisation
Full text linkNowadays, worldwide low-alcohol and alcohol-free beer markets are growing rapidly, and this leads to a strong demand of improved technologies for their production. Among the various membrane-based processes, a dialysis in diafiltration mode, with no transmembrane pressure difference, has been chosen as first step of a combined process for beer dealcoholisation which includes a pervaporation stage to recover aroma compounds which are then integrated to the final low-alcohol beer. The results of experimental tests for the optimization of beer diafiltration process using a bench scale unit and two different membranes of cellulose and polyacrylonitrile are shown in this work. A commercial lager beer has been dealcoholized, in a discontinuous diafiltration mode, interweaving concentration and dilution stages, up to an alcohol content lower than 1.2 %vol., which is the residual alcohol content for low alcohol beverages in European countries. Various dialyzing solutions and operating parameters (e.g., temperature, flow rate, volumetric concentration ratio) were tested in order to improve the ethanol removal from the beer. The physical-chemical characteristics of the beer such as pH, electrical conductivity, density and colour and free-phenolic profile, before and after the dealcoholisation process were evaluated. Results showed no substantial differences between the membranes tested for the dealcoholisation process and small differences in the physical and chemical characteristics of beer before and after the treatment
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