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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Author: search.filters.author.Curcio, EfremSubject: search.filters.subject.Ingegneria chimica

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    Modelling study of vanadium based alloys and crystalline porous materials for gas separation membranes
    (2016-02-26) Borisova Evtimova, Jenny; De Luca, Giorgio; Curcio, Efrem; Molinari, Raffaele
    Gas! membrane! separation! is! an! attractive! technology! that! is! often! superior! to! other! more! conventional! procedures! for! separation! of! gaseous! species! in! terms! of! energy! consumption! and! environmental! impact.! A! key! factor! for! membrane! separations! is! the! membrane! itself! with! its! properties,! which! determine! the! overall! performance! of! the! process.! One! essential! membrane! characteristic!is!the!transport!selectivity.!High!separation!factors!are!especially!difficult!to!achieve! for! mixtures! of! light! gases! having! comparable! kinetic! diameters.! Moreover,! high! permeability,! correspondingly! high! solubility! and! diffusivity! in! dense!membranes,! are! crucial! aspects! for! the! performance! and! further! practical! application! of!membrane! devices.! In! this! frame,! the!material! used!as!a!selective!layer!is!determinant.!Therefore,!scientists!devote!immense!efforts!to!the!search! of! optimal! gasBsorbent! combinations,! including! thorough! study! of! existing! structures! and! elaboration!of!new!ones!with!sieving!properties.!The!large!effort!and!time!required!for!preparation! and!experimental!testing!of!materials!impede!the!advancement!of!new!membranes.! In!this!study,!we!propose!procedures!based!on!computational!calculations!and!theoretical!models! that! can!be!used! to!predict! the!behaviour!of! some!of! the!membrane!materials!of! interest! for! gas! separation! applications.! In! particular,! we! focus! on:! i)! bodyBcentred! cubic! VNiTi! alloys! as! novel! materials!for!H2Bselective!dense!membranes!and!ii)!crystalline!porous!materials!that!are!attractive! media!for!separation!of!light!gases!such!as!H2,!O2,!CO,!CO2,!CH4!and!N2.!These!two!types!of!materials! are! treated! using! different! methodologies,! adapted! to! the! needs! of! our! research! objectives! associated!to!each!material.! In!the!case!of!dense!metal!membranes,!the!long!standingBcontroversy!over!occupancy!of!interstitial! hydrogen! in! VBbased! alloys! is! addressed.! The! VBNiBTi! system! is! of! particular! interest! here,! exhibiting!high!H2!permeability!and!improved!mechanical!properties!relative!to!pure!V.!This!work! intends!to!gain!understanding!of!hydrogenBmetal!interactions!as!function!of!alloy!composition!and! thereby!to!optimize!these!new!materials!and!advance!their!development!as!novel!membranes!for! H2! separation.!We! use! a! firstBprinciples! approach! that! gives! insights! into! the! sites! preference! of! hydrogen! and! assesses! the! role! of! Ti! and! Ni! substitutional! solutes! for! the! hydrogen! absorption! affinity.! The!method! based! on!Density! Functional! Theory! requires! no! experimental! input! except! crystal!structure!information.!Furthermore,!it!uses!no!empirical!or!fitting!parameters!in!contrast!to! other!computational!techniques.!Hence!this!approach!provides!an!alternative!way!to!explore!new! metal!alloys!for!H2!separation!membranes.!The!applied!methodology!can!be!used!further!in!highB throughput!calculations!to!screen!various! alloy!compositions.!The!heretoBreported!results!will!be! used!as!guidance!for!tailoring!the!formulation!of!VNiTi!solid!solutions!and!preparation!of!low!cost†! dense!alloy!membranes!in!the!frame!of!other!projects!(e.g.!European!DEMCAMER!project).! Further,! we! explore! how! singleBcomponent! inputs! can! be! used! to! forecast! the! ideal! selectivity! towards! light! gases! of! crystalline! porous!materials,! used! for!membrane! preparation.! Theoretical! models! for! describing! gas! separation! properties! of! zeotype! materials! as! function! of! structural! characteristics!and!operation!conditions!are!proposed.!The!model!parameters!can!be!obtained!as! experimentally!as!well!as!computationally.!To!analyse!the!extent!of!validity!and!limitations!of!the! models,!ideal!selectivities!of!few!crystalline!porous!materials!are!evaluated,!including!widely!used! zeolites!(NaA,!CaA)!and!a!metal!organic!framework!structure!(ZIFB8).!The!results!verified!that!the! theoretical!expressions!could!be!used!for!screening!series!of!zeotype!materials!when!reliable!single! gas!adsorption!data!are!available.!However,!since!the!models!don’t!take!into!account!all!parameters! (namely! related! to! the! membrane! design)! and! mechanisms! involved! in! gas! transport! through! porous!membranes,!their!predictions!should!be!considered!as!values!referring!to!an!ideal!case.!
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    Bio-Hybrid Membrane Process for Food-based Wastewater Valorisation: a pathway to an efficient integrated membrane process design
    (2014-11-11) Gebreyohannes, Abaynesh Yihdego; Giorno, Lidietta; Curcio, Efrem; Aimar, Pierre; Vankelecom, Ivo F.J.; Molinari, Raffaele
    The food industry is by far the largest potable water consuming industry that releases about 500 million m3 of wastewater per annum with very high organic loading. Simple treatment of this stream using conventional technologies often fails due to cost factors overriding their pollution abating capacity. Hence, recently the focus has been largely centered on valorization through combinatorial recovery of valuable components and reclaiming good quality water using integrated membrane process. Membrane processes practically cover all existing and needed unit operations that are used in wastewater treatment facilities. They often come with advantages like simplicity, modularity, process or product novelty, improved competitiveness, and environmental friendliness. Thus, the main focus of this PhD thesis is development of integrated membrane process comprising microfiltration (MF), forward osmosis (FO), ultrafiltration (UF) and nanofiltration (NF) for valorization of food based wastewater within the logic of zero liquid discharge. As a case study, vegetation wastewater coming from olive oil production was taken. Challenges associated with the treatment of vegetation wastewater are: absence of unique hydraulic or organic loadings, presence of biophenolic compounds, sever membrane fouling and periodic release of large volume of wastewater. Especially presence of biophenolic compounds makes the wastewater detrimental to the environment. However, recovering these phytotoxic compounds can also add economic benefit to the simple treatment since they have interesting bioactivities that can be exploited in the food, pharmaceutical and cosmetic industries. The first part of the experimental work gives special emphasis on the development of biohybrid membranes used to control membrane fouling during MF. Regardless of 99% TSS removal with rough filtration, continuous MF of vegetation wastewater using 0.4 μm polyethelene membrane over 24 h resulted in continuous flux decline. This is due to sever membrane fouling mainly caused by macromolecules like pectins. To overcome the problem of membrane fouling, biocatalytic membrane reactors with covalently immobilized pectinase were used to develop self-cleaning MF membrane. The biocatalytic membrane with pectinase on its surface gave a 50% higher flux compared to its counterpart inert membrane. This better performance was attributed to simultaneous in-situ degradation of foulants and removal of hydrolysis products from reaction site that overcome enzyme product inhibition. Although the biocatalytic membrane gave a better performance, its fate is disposal once the covalently immobilized enzyme gets deactivated or oversaturated with foulants. To surmount this problem a new class of superparamagnetic biochemical membrane reactor was developed, verified and optimized. This development is novel for its use of superparamagnetic nanoparticles both as support for the immobilized enzyme and as agent to render the membrane magnetized. This reversible immobilization method was designed to facilitate the removal of enzyme during membrane cleaning using an external magnet. Hence PVDF based organic-inorganic (O/I) hybrid membrane was prepared using superparamagnetic nanoparticles (NPSP) as inorganic filler. In parallel, superparamagnetic biocatalytic nanocomposites were prepared by covalently immobilizing pectinase on to the surface of NPSP dispersed in aqueous media. The synergetic magnetic responsiveness of both the O/I hybrid membrane and the biocatalytic particle to an external magnetic field was later on used to physically immobilize the biocatalytic particles on the membrane. This magnetically controlled dynamic layer of biocatalytic particles prevented direct membrane-foulant interaction, allowed in-situ degradation, easy magnetic recovery of the enzyme from the surface of the membrane, use of both membrane and immobilized enzyme over multiple cycles and possibility of fresh enzyme make up. The system gave stable performance over broad range of experimental condition: 0.01-3 mg/mL foulant concentration, 1-9 g per m2 of membrane area bionanocomposites, 5- 45 L/m2.h flux and different filtration temperatures. Under condition of mass transfer rate prevailing reaction rate, the system gave upto 75% reduction in filtration resistance. After optimization of the different operational parameters, it also revealed no visible loss in enzyme activity or overall system performance, when 0.3 mg/mL pectin solution was continuously filtered for over two weeks. In addition, the chemical cleaning stability of the O/I hybrid membrane was studied under accelerated ageing and accelerated fouling conditions. The ageing caused change in the physicochemical characteristics and enhanced fouling propensity of the membrane due to step-by-step degradation of the polymeric coating layer of used NPSP. But 400 ppm NaOCl solution at pH 12 was found compatible; henceforth it was used to clean the membrane. Second major limitation identified during the treatment of vegetation wastewater is presence of large volume of wastewater that comes in short period following the harvest of olive fruit. To alleviate this problem, FO was investigated to concentrate the wastewater. This process is believed to be less energy demanding, suppose that draw solution does need to be regenerated, and with low foul propensity. By operating at 3.7 molal MgCl2 draw solution and 6 cm/s crossflow velocity, single-step FO resulted in an average flux of 5.2 kg/m2.h. and 71% volume concentration factor with almost complete retention of all the pollutants. Moreover, the system gave a stable performance over ten days when operated continuously. After FO, both NF and UF were used to fractionate the recovered biophenols from the concentrate streams of FO. Compared to polymeric UF membrane, ceramic NF gave better flux of 27 kg/m2.h at 200 L/h feed flow rate and 7 bar TMP. Finally, when FO was used as a final polishing step to recover highly concentrated biophenols from permeate of the UF; it gave an average flux of 5 kg/m2.h and VCF of 64%. In conclusion, a great success has been made in tackling the two most important challenges of vegetation wastewater valorisation using the concept of biohybridization and FO. The bioinspired NPSP provides strong evidence that magnetically controlled enzyme immobilization have an immense potential in membrane fouling prevention and paves a potential breakthrough for continuous wastewater filtration. By setting bio-inspired NPSP biocatalytic membrane reactor at the heart, it is possible to successfully use integrated membrane process for continuous valorisation of food based wastewater. In addition to fouling prevention, they open a new horizon for applications in localized biocatalysis to intensify performance in industrial production, processing, environmental remediation or bio-energy generation.
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    Realizzazione di membrane polimeriche innovative per la crescita in vitro di tessuti umani
    (2010-11-12) Campana, Carla; De Bartolo, Loredana; Curcio, Efrem
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    Membrane Distillation in Integrated Seawater Desalination Systems
    (12-11-2010) Ji, Xiaosheng; Drioli, Enrico; Curcio, Efrem; Molinari, Raffaele
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    Process intensification:integrated membrane operations for brackish and seawater desalination
    (2014-06-10) Al-Obaidani, Sulaiman; Drioli, Enrico; Curcio, Efrem; Molinari, Raffaele
    The present research study is focusing on the evaluation of the integrated membrane system which merges the membrane contactor technology such as gas-liquid membrane contactors (GLMC) and membrane distillation /crystallization (MD/MDC) with the conventional pressure-driven membrane operations such as micrfiltration/ultrafiltration (MF/UF), nanofiltration (NF) and reverses osmosis (RO) within the logic of Process Intensification (PI) strategies in order to redesign the desalination plants to be cheaper, safer and sustainable. The importance of applying the PI strategies in the desalination industry is presented in chapter 1. In addition, this chapter gives the research project objectives and activities. The optimization and the feasibility of using the GLMC in the proposed integrated membrane system were discussed in chapter 2. Simulation model for the GLMC was implemented by computer and the results were verified by experimental tests. The results showed that there was a good agreement between the simulation and experimental results with less than 10% differences. In terms of CO2 transfer rate, the results showed that higher transfer rates were obtained at higher liquid flow rates and higher pH values due to lower mass transfer resistance and higher reaction rates, respectively. The feasibly study showed that using GLMC is more economically feasible since the cost of the NaOH used in the GLMC after reacting with CO2 to produce Na2CO3 was less than the cost of using Na2CO3 directly from the market in order to precipitate Ca+2 as CaCO3. Moreover, the GLMC will contribute to the reduction of CO2 emission from desalination plants and reduce their environmental impact. Since so far there are no membrane modules especially made for MD, the aim of this study was to provide optimization guidelines for materials and methods for using MD in desalination. Therefore, in chapter 3, comprehensive theoretical analysis have been carried out and simulation model was developed to describe the mass flux and heat efficiency in MD processes considering transport phenomena, membrane structural properties and most sensitive process parameters, with the aim to investigate the effects of the membrane properties on the MD performance and to set some criterions to optimize these properties in order to obtain the best performance. Experimental tests were conducted in order to validate the results obtained by the computer simulation and the results showed that the computer simulations were able to estimate the MD performance with errors not exceeding 5%. The results showed that an increase of the temperature gradient resulted in the enhancement of both transmembrane flux and thermal efficiency. On the other hand, feed concentration had low effects in flux reduction even at high values close to saturation which contribute to only 30-50% flux reduction. This makes the MD ii process attractive technique for seawater desalination especially when integrated with RO in the logic of the ZLD concept and satisfying the process intensification goals. The investigation of the effects of membrane properties confirmed that better MD performance was achieved when using polymeric membranes characterized by low thermal conductivity (flux and thermal efficiency declined by 26% and 50%, respectively, when increasing thermal conductivity from 0.1 to 0.5 W/m K), lower thickness (increasing the membrane thickness from 0.25 to 1.55 mm resulted in a flux decay of about 70% without a significant improvement in thermal efficiency), and high porosity. The investigation of the complex correlations between physico-chemical properties of the membrane and MD performance confirms the need for a customized hardware, i.e. high porosity hydrophobic membranes with appropriate thickness and made by low-heat conductive polymers in order to reduce the amount of wasted energy. The basic mechanisms and kinetics of crystallization were considered in chapter 4 in order to accomplish the modeling and simulation for the membrane crystallizers. The computer simulation of the MDC was similar to the one of the MD presented in chapter 3 with addition of crystallization kinetics calculation. The simulation model was used in parallel with the experimental tests in order to improve the design and performance of the crystallizers. The results showed that it was possible to obtain NaCl crystals from the NF retentate at a good quality and narrow crystal size distribution (CSD). The effects of the concentration polarization in the transmembrane flux were very limited; however, there was an unexpected flux decline after the formation of the crystals in the system. This was due to the deposition of the salts crystals on the membrane surface which caused pore blockage and hence flux drop. The design improvement of the MDC suggested to introduce another opening at the bottom of the crystallizer tank for removing crystals, and to install a filter in the suction side of the feed pump in order to avoid crystals for recirculation inside the membrane module with the feed. Exergy analysis, economical investigation and sensitivity study were carried out in chapter 5 to evaluate the feasibility of the integrated membrane system. The exergy analysis showed that the highest work input was for the plant which involved the pressure-driven membranes UF-NF-RO due to the high pumping and pressurizing energy requirement especially in NF and RO pumps. On the other hand, the highest heat energy input was associated with the membrane distillation plant as a stand alone process. The exergy efficiency was generally higher in case of pressure-driven operations than thermal processes. In addition, the performance of plants with energy and heat recovery systems was always better than the ones without energy and heat recovery systems. Economical study and cost evaluation for several configurations showed that the lowest total water costs were 0.51 and 0.29 $/m3 when using UF-RO plant with energy recovery system for seawater and brackish water desalination, respectively. In case of the integrated system which contained both pressure and thermal processes, the best combination was obtained when using the pressuredriven membranes combined with a membrane crystallization unit operating on the NF concentrated stream and a membrane distillation unit operating on the RO brine stream. The total water cost in this case was 1.27 $/m3 and 1.10 $/m3 for seawater and brackish water, respectively. Moreover, the combination of membrane crystallization units is very attractive especially if the salt crystals produced by the crystallization process are considered. This means that the desalination plant will produce both water and salt crystals. In this case, the price of the salts can cover the whole expenses of the desalination process. Besides, the problems related to brine disposal were minimized when using the integrated membrane system. The sensitivity analysis revealed that the pressure-driven membrane operations were very sensitive to the feed concentration and the cost of electricity. On the other hand, MD processes were not sensitive to the variation on the feed concentration or the electricity costs. The most sensitive parameter in the total water cost of the MD plant was the cost of steam which contributed to values as high as high as 11.4% in case of MD without heat recovery system. The best tolerance to the variation of these parameters was obtained when using the integrated membrane system of pressure-driven membranes and MD/MDC processes. The realization of the semi-pilot plant of the integrated membrane system was covered in chapter 6. The semi-pilot plant of the integrated membrane system was designed and assembled based on the results obtained by the computer simulations and the preliminary experiments done for each unit individually in the previous chapters. It consisted of UF-NF-RO as the pressuredriven membrane operations with the GLMC for Ca+2 precipitation and an MDC unit which can be operated as an MD or as a membrane crystallizer. The semipilot desalination plant of the integrated membrane system was operated using synthetic and real seawater in order to confirm the performance and process stability. The transmembrane flux was stable during the operation. The MDC was able to produce salt crystals from the NF retentate and the RO brine streams. The CSD of the crystals obtained by the MDC operating on the RO brine showed sharper distribution trends than the ones obtained from the MDC when operating on the NF retentate. In addition, the MD unit was operated as a standalone desalination process using real seawater and the results showed that it was stable and the membrane did not loss its hydrophobicity during the operation