Dipartimento di Ingegneria dell'Ambiente - Tesi di Dottorato
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Questa collezione raccoglie le Tesi di Dottorato afferenti al Dipartimento di Ingegneria per l'Ambiente e il Territorio e Ingegneria Chimica dell'Università della Calabria.
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Item Experimental investigation of system performance for combined desalination processes with membrane capacitive deionisation (MCDI)(Università della Calabria, 2021-10-31) Cañas Kurz, Edgardo E.; Critelli, Salvatore; Gabriele, Bartolo; Figoli, Alberto; Hoinkis, JanThe water supply in many coastal regions worldwide is affected by progressive salinization. Here, the use of desalination technologies is a viable solution for obtaining freshwater. In this thesis, two modular concepts for brackish water (BW) desalination by the use of membrane capacitive deionization (MCDI) and low-pressure reverse osmosis (LPRO) were developed and tested at laboratory and pilot-scales with two pilot plants installed in Vietnam. The two concepts were developed by using computer-based calculations (software: WAVE) and evaluated in a socioeconomic and environmental multi-criteria analysis. The first plant consisting of subsurface arsenic removal (SAR) as pre-treatment and MCDI for desalination was installed in Tra Vinh, in the Mekong Delta for the treatment of arseniccontaminated groundwater with a concentration of total dissolved solids (TDS) of 1.65 g/L. Results showed the feasibility of the modular concept for producing drinking water (TDS<0.45 g/L) with a specific energy consumption (SEC) of <3 kWh/m³. The relationship between feed salinity and specific ion removal of the MCDI was evaluated in real environment and compared with laboratory experiments. The use of renewable energies such as solar and wind for autonomous supply was proven feasible for these technologies. The second pilot plant was installed in a riverine estuary in the region of Cần Giờ, where no access to freshwater is available due to the progressive salinization of river water and groundwater. Here, river water showed TDS concentrations of up to 25 g/L. The combined system consisted of UF pre-treatment, LPRO and MCDI to produce drinking water and product water with TDS of <0.45 g/L and <1.5 g/L, respectively with a total SEC of 5.8 kWh/m³. Additionally, the performance of the LPRO was compared to seawater-RO (SWRO) in pilot trials, which showed a SEC of 5.5 kWh/m³. Although the SEC of single-stage SWRO was lower, the separate production of drinking and product water by LPRO+MCDI showed different advantages including a reduced SEC of 5.2 kWh/m³ for product water and additional 0.6 kWh/m³ for drinking water. Finally, an optimization of the LPRO+MCDI can be possible by increasing the desalination efficiency of the MCDI, increasing the efficiency of LPRO-pump and the MCDI power supply, and by aiming at feed water qualities with lower salinity.Item Theoretical Models for Membrane Capacitive Deionization for the design of Modular Desalination Processes(Università della Calabria, 2021-12-08) Hellriegel, Ulrich; Critelli, Salvatore; Gabriele, Bartolo; Figoli, Alberto; Hoinkis, JanDue to climate change, water scarcity will be exacerbated around the globe. To increase the water availability in regions at risk, water desalination plants can be a solution. Especially in rural areas, energy e cient technologies are needed so that an operation with renewable energy as photovoltaic modules can be feasible. Recent publications showed that the novel technology membrane capacitive deionization (MCDI) can achieve a lower speci c energy consumption (SEC) than reverse osmosis (RO), for brackish water desalination with salt concentrations below 2.5 g L-1. There is still a gap in research between laboratory operation and applied commercial scaled desalination, regarding experimental but also theoretical model studies. Therefore the latter is elaborated in the present PhD thesis. Hereby, existing models are reviewed, adapted and further developed to t to applied MCDI operation for drinking water production. Two dimensional nite element methods (FEM) modelling of ion transport, according to the Gouy-Chapman-Stern theory for electrical double layers (EDL) as well as computational uid dynamics (CFD) is combined with an adjusted semi-analytical modi ed Donnan (mD) model, with a constant excess chemical potential att = 2:33 kT, for the electrosorption of ions into porous active carbon electrodes. It predicts the e uent salt concentration time-dependently for di erent inputs of applied electrical currents Icell and voltages as well as inlet concentrations and volume ows. Applied MCDI operation was optimized for drinking water production with practical experiments, which support the evaluation of the theoretical ndings. The model ts to experimental data for Icell = 20 A, however the equations for the voltage over the electrodes need to be re-assessed so that the model ts for further input parameters. A CFD model of the water ow through large scaled MCDI modules (> 50 pairs of electodes) shows the need of constructing spacer thicknesses Sp small enough, to ensure equal retention times of the water between the electrodes in the module, which is important for stable diluate concentrations. Furthermore, an analytical calculation tool is developed, by adjusting the mD model and introducing an e ective salt adsorption capacity salt; , to predict the maximum e cient charging time tmax,ch, removal- and recovery rate as well as SEC values for optimized operation of applied MCDI processes. The model reaches an accuracy of 87% for the prediction of salt removal, 86% for tmax,ch and 75% for SEC values, compared with an experimental study and thus can be used to optimize the process design of applied MCDI desalination plants.Item Innovative UV-LED polymerised bicontinuous microemulsion coating for membranes with special emphasis on MBRs(2017-07-11) Schmidt, Slefan-André; Pantano, Pietro; Curcio, Efrem; Gabriele, Bartolo; Figoli, AlbertoThe main objective of this work is the preparation of polymerisable bicontinuous microemulsion (PBM) coatings applied onto commercial membranes for improving the anti-fouling properties and performance, in terms of water flux and foulants rejection. Microstructured and nanostructured materials obtained by PBM have been widely investigated in the course of the last 30 years. The interest in microemulsion lies mainly in the possibility of dissolving larger amounts of oil and water by using polymerisable and non-polymerisable surfactants. By polymerising the bicontinuous microemulsion it is possible to produce transparent porous polymeric solids [Gan et al. (1995), Gan and Chew (1997)]. This thesis represents the follow-up of the work done by Galiano et al. (2015) and Deowan et al. (2016). Galiano et al. (2015) developed the PBM composition that based on a non-polymerisable surfactant (DTAB) and another polymerisable surfactant (AUTEAB). In their work the PBM was polymerised by redox initiators leading to a process that is very difficult to up-scale for a commercial application. Critical issues were, the polymerisation time (at least 20 minutes), and the reproducibility of the coating. Therefore, it is the aim of this work to develop another polymerisation technique that increases the polymerisation speed and allows the easy reproduction of membranes with defined properties. The polymerisation by photoinitiators excited by UV-light represents a promising possibility for this requirement as it has the potential of decreasing the polymerisation time down to a few seconds. Several photoinitiators were selected for their compatibility with the PBM, and studied for their conversion rate efficiency (section 5.1.5). As there is a wide range of potential UV-light sources available, several technologies are studied for their coating performance (section 5.1.3). Subsequent to that, experiments were done in order to define the ideal photoinitiator type and concentration while polymerising onto glass plates. The coating onto commercial membranes is studied deeply for e.g. different casting knife thickness or ambient temperature (section 5.2.2 As the polymerisation under inert conditions is expected to increase the polymerisation speed, experiments are done, both under inert and non-inert conditions. The final membrane, coated under the optimum conditions, is further characterised for their permeability under different conditions like transmembrane pressure (TMP), model foulant experiments and a fixed volume flow (section 5.2.3). Further characterisation is done by contact angle, SEM, AFM (section 5.2.5 to 5.2.7). The prepared PBM membranes are foreseen to be finally applied for model textile dye wastewater treatment by Membrane BioReactor (MBR) technology. According to the previous results of Deowan et al. (2016) higher permeate quality through increased COD, TOC, dyestuffs removal efficiency and stronger anti-fouling properties are expected. Consequently, lower operation/maintenance costs due to reduced necessary aeration for scouring purposes and reduced membrane cleaning cycles as well as less membrane replacement are of special interest for commercial applications. In the previous work of Deowan et al. (2016) a lab scaled MBR with a single membrane housing was used. As of the biocenosis of the bacteria inside the reactor tank, a comparison of the membrane performance of the PBM and commercial membrane is difficult to achieve. Therefore an existing MBR system was redesigned to allow the simultaneous run of a commercial and a PBM coated membrane (section 4.1). As the revamp requires also additional sensors, the data acquisition needs to be adapted as well. To assure the proper function of the MBR the system was running for long term with two commercial membranes using a model textile wastewater (see 5.3.2). Finally the PBM coated membrane was compared with a commercial one for their performance in the MBR. Initial experiments for the water permeability are done as preparation for future work (see 5.3.3).Item Preparation of mixed matrix membranes for water treatment(2017-07-11) Grosso, Valentina; Panano, Pietro; Drioli, Enrico; Fontananova, Enrica; Di Profio, Gianluca; Curcio, Efrem; Gabriele, BartoloThe treatment of wastewater and its reuse is a very important topic in industrial processes. This because not only avoids drawing on natural resources, but also enables a significant reduction in the amount of wastewater discharged into the natural environment. Wastewater can also be used for various purposes where drinking water quality is not mandatory, including agricultural irrigation, the cleaning of industrial equipment, the watering of green spaces, and street maintenance, etc. In fact, the water reuse has become essential in all areas in the world that suffer from water shortages [1]. Different methods are used for wastewater treatment. These processes can be to divide in: primary, secondary and tertiary treatment. Primary treatment (screening, filtration, centrifugation, sedimentation, coagulation, gravity and flotation method) includes preliminary purification processes of a physical and chemical nature while secondary treatment deals with the biological treatment of wastewater. In tertiary treatment process wastewater is converted into good quality water that can be used for different types of purpose, i.e. drinking, industrial, medicinal etc. supplies [2]. The complexity of industrial processes, the variety of pollutants and the limitation of a single operation, has led to the need for more complex processes and especially to a combination of processes. Membranes technologies falls on the tertiary water treatment technologies and are actually the most effective separation processes and they are still in rapid development creating new prospects of their applications in clean technologies [3]. The utilization of membrane operations as hybrid systems, i.e. in combination with other conventional techniques or integrated with different membrane operations is considered the way forward for more rationale applications [4]. The possibilities of redesigning various industrial cycles by combining various membrane operations have been studies and in some case realized with a low environmental impact and a low energy consumption [5]. Different processes can be used in various steps of a hybrid system, depending from the size of the pollutants to be removed. Microfiltration (MF) and ultrafiltration (UF) membrane processes, can be used as pre-treatment, while nanofiltration (NF) and reverse osmosis (RO) can used in the final step of the integrated system to remove particles with smaller dimensions (Chapter 1) The membranes have different morphological characteristics that affect their performance. The study of all the conditions which modulate these characteristics is a crucial point in the choice of membranes to be used in the various separation processes. Therefore, it is important to investigate about new materials and new types of membranes, like as mixed matrix membrane (MMM). MMM is a heterogeneous membrane consisting of inorganic fillers embedded in a polymeric matrix and can be made into flat sheets and hollow-fiber. Nevertheless, the selection of membrane configuration is greatly dependent on the application and therefore the production of MMMs in useful configuration is undoubtedly a crucial point in membrane development [6]. Also, the selection of inorganic fillers depends of desired membrane performance and their use. More attention was focus on the interesting characteristic of carbonanotubes (CNTs) (chapter 2). CNTs themselves have remarkable electrical, thermal, and mechanical properties. These nanotubes have the structure of a rolled-up graphene sheet with smaller diameter. Multiwalled carbonanotube (MWCNTs) were used to prepare MMMs for wastewater treatment. Different compounds, as additives in the polymeric membranes were used in high percentage; in the case of MWCNTs was observed as a low amount can change the membrane morphologies, mechanical and transport properties. A crucial point was the choice of membrane materials. Two type, hydrophilic poly(imide) (PI) and hydrophobic poly(vinylidenfluoride) (PVDF) were choose for membrane materials to produce MMMs. Another important point in this study was the use of functionalized MWCNTs that provide a good dispersion in the casting solution first, and in the polymeric matrix after phase separation. The main limitation in the use of CNTs is their poor dispersion in the main solvents used for the preparation of membranes. The functionalization has been proven an efficient method to overcome this limitation improving the compatibility with the polymer matrix. The presence of polar groups on the carbon nanotubes can reduces their tendency to aggregate by van der Waals interactions, while forming hydrogen bonds and electron donor/acceptor interactions with the polymer. Low percentages of CNTs were used for the preparation of membranes. These percentages were sufficient to improve better performance to modified membranes. PI was select as polymeric materials because combine easy processability in the form of membranes, with a high chemical and thermal stability, over a wide range of operative conditions. Three different PI polymers were used to prepared porous asymmetric membrane by non-solvent induced phase separation (NIPS): a homopolymer (Matrimid) and two co-polymers (Lenzing P84 and Torlon). The effect of membrane preparation conditions on the membrane morphology and transport properties, were investigate. Moreover, mixed matrix based on co-polyimide P84 and functionalized multiwalled carbon nanotubes (oxidized and aminated MWCNTs) were prepared. The different polymeric membranes were compared in the rejection of organic dyes, as model of organic pollutant present in wastewater (chapter 3). To investigate about the influence of functional groups on the MWCNTs for their interaction with polymeric matrix, three different type of functionalized MWCNTs (oxidized, amined and aminated) were dispersed also in polymeric hydrophobic PVDF membranes. PVDF was selected as polymeric materials of its outstanding properties: excellent chemical resistance and hydrolytic stability; high mechanical strength and stability over a broad pH range; polymorphism (main crystalline phases are: α, β, γ, δ and ε) [7]. The aim was to tailor the interactions with the polymeric matrix in order to realize high performing composite film with improved performance. Bovine serum albumin (BSA) protein was select as compound to evaluate the membrane performance. In particular, the antifouling properties and the permeation flux of mixed matrix membranes, were evaluate as well as thermal and structural and mechanical properties (chapter 4).