Browsing by Author "De Luca, Giorgio"

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Experimental and theoretical study of polyhedral carbon Nano-Onions
(2018-02-23) Basantes Valverde, Marlon Danilo; Pantano, Pietro; Caputi, Lorenzo; De Luca, Giorgio
Carbon nano-onions (CNOs), in their spherical or polyhedral forms, represent an important class of nanomaterials due to their peculiar physical and electrochemical properties. Among the different methods of production, arc discharge between graphite electrodes sustained by deionized water is one of the most promising to obtain good quality CNOs. The arc discharge method is applied to optimize the production of CNOs, and the synthesized nanomaterials by TEM was studied. An innovative experimental arrangement is used to obtain CNOs dispersed in water together with other carbon nanomaterials, and a black hard cathodic deposit. A simple mechanical grinding of the deposit it allowed to obtain turbostratic polyhedral CNOs with different aspect ratios, which exhibited higher stability towards burning in air, compared to CNOs found in water. A mechanism for the formation of the CNOs contained in the deposit, different from the generally accepted mechanism responsible for the synthesis of CNOs dispersed in water, is hypothesized. These spherical or polyhedral multi-shell fullerenes are widely studied owing to their interesting electronic and mechanical proprieties; nevertheless, comparative studies on these nanoparticles remain scarce. Herein, some key electronic proprieties of single and double walled icosahedral fullerenes as function of their sizes were calculated in the frame of the Density Functional Theory. In particular, structures of icosahedral polyhedral fullerenes, previously validated, were used to get the gap between the Highest Occupied Molecular Orbital and the Lowest Unoccupied Molecular Orbital levels (H-L gap), electron affinity, first ionization potential, electronegativity as well as the Density of the electronic States. This work shows that the H-L gap of the single-wall fullerenes decreases as the nanoparticles size increases, whereas an opposite trend was obtained for the double walled fullerenes. Going from single to double wall nanoparticles; a systematic and marked decrease of the H-L gap was found although, this difference reduces increasing the size of the double walled up obtaining an inversion. The DOS structures of SW nanoparticles changes radically adding a second shell, and the extent of these changes depends on the sizes of the analyzed fullerenes
Modelling of nanostructured membranes for wasterwater purification
(2013-11-29) Bisignano, Federica; Bartolino, Roberto; De Luca, Giorgio
The removal of pollutants as well as the recovery of high added value molecules with low molecular weight is a current challenge in the wastewater treatment. Membrane processes can be considered as a viable option to solve these issues. In separations based membranes, high rejection of organic matter and water high permeability are two very important aspects that must be optimised. In general, the increase of the former comes at the expense of the latter because high rejection is cause of membrane fouling which in turns reduces dramatically the water permeability. Thus, membrane fouling constitutes one of the major limitations in membrane separation processes. The design of innovative materials which show high water permeability and at same time molecular rejection but with a low propensity to fouling is of fundamental relevance in this area. Mixed-matrix composite membranes where nanostructures such as Carbon Nano Tubes (CNTs) or Nano particles (NPs) are added, are receiving a huge focus since the properties of these nanostructures can confer an increase of the membrane efficiency in terms of permeability, selectivity, resistance and finally antifouling. The choice of the right nanomaterial can be highly accelerated by computational modelling. Thus, in this thesis an ab-initio modelling study in the frame of the Density Functional Theory (DFT) is carried out in order to investigate the structure-property relationships of nanostructures like CNTs and polyoxometalates NPs (POM). These nanostructures are used in the preparation of composite membranes in the frame of BioNexGen project [1] with the aim to propose novel membranes to be used in bioreactor for industrial waste water treatment. In particular, the rejection of CNTs towards organic solutes with low molecular weight coming from industrial waste water such as cosmetic, textile and oil olive was analysed in conjunction to the optimization of water permeability in CNTs. Also, the adsorption of POMs on polymeric membrane surface was analysed in order to understand if an efficient antifouling property can be imparted to the membranes by adding these NPs which possess excellent antibacterial and oxidants properties. While nanotube permeability has been extensively studied in both experimental and modelling works resulting in orders of magnitude water flow enhancements for tube diameters in the reverse osmosis and nanofiltration range [2], less work has been done on CNT selectivity of small organic solutes. Precise control of the CNTs synthesis allows for fine-tuning of the outer and inner diameters in the case of single- and multi-wall carbon nanotubes (SWNTs and MWNTs, respectively), offering the possibility of controlling their selectivity toward small solutes. In this thesis a modelling study was, therefore, addressed to define the optimal CNT internal diameter that should be used in order to achieve a total rejection of several target compounds very difficult to separate. Three novel algorithms [3, 4] were implemented during the thesis for reach the aforementioned objective. These algorithms do not make use of any adjustable parameters (i.e. fitting parameters) being based on geometry optimizations carried out in the frame of high level of quantum approach (DFT) and topological analysis of the considered systems. In addition, the CNTs geometrical characteristics should be optimized in order to get the best compromise between permeability and rejection. The functionalizing of the nanotubes tip with specific functional groups capable of hindering the passage of solutes while allowing water molecules to flow has been suggested as a solution to this problem [5, 6]. Thus, a theoretical study of CNT-composite membranes was carried out in this work with the aim of optimizing the CNTs tip, through their functionalization, to maximise both water permeability and solutes selectivity. This study is the basis of the third implemented algorithm [7]. Concerning the membrane fouling, the analysis of the adsorption of antibacterial anionic NPs (i.e. POM) on the surface of polymeric membranes was carried out in this thesis in order to achieve an optimal adsorption of these NPs. Noncovalent interactions between POM and commercial surfactants, used in polymer membrane preparations, were evaluated. Anionic POMs are in fact promising antibacterial agents [8], therefore, an efficient exchange with the bromide ions, used to counterbalance the positive charge of the commercial surfactants, would allow to increase the efficiency of the membrane by reducing the organic and bio fouling. In order to achieve this result, besides the aforementioned POM-surfactants noncovalent interactions the electronic hydration energy of POM and bromide anions was also evaluated in order to predict the probable exchange of these anions on the polymer surface. The conclusions of this thesis are achieved by using only ab-initio methods thus the results can be considered quite generals and homogeneous, free from empirical or fitting parameters. A validation of the theoretically prediction is provided concerning the POM-bromide exchange by means of an ad hoc designed experiment. The experimental results are in agreement with the theoretically predictions
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.!
Molecular modelling of imprinted membranes prepared by the noncovalent approach
(2011-10-08) Garcia Del Blanco, Samuel; Drioli, Enrico; De Luca, Giorgio; Molinari, Raffaele
A multi-scale theoretical paradigm to model the complex interactions between macromolecules and polymeric membranes membranes
(Università della Calabria, 2020-03-29) Petrosino, Francesco; Crupi, Felice; Curcio, Stefano; De Luca, Giorgio
The overall aim of the work was to provide a complete Multiscale Model of macromolecules interactions to simulate different processes and bioprocesses where such interactions, among different macromolecules and between macromolecules and polymeric surface, strongly determine the system behaviour. The adsorption of proteins on material surfaces is an essential biological phenomenon in nature, which shows a wide application prospect in many fields, such as membrane based processes, biosensors, biofuel cells, biocatalysis, biomaterials, and protein chromatography. Therefore, it is of great theoretical and practical significance to study the interfacial adsorption behaviour of proteins and their structuration and aggregation in order to describe concentration polarization phenomena in separation processes. It is worthwhile remarking that ab-initio simulations allow the estimation of parameters without exploiting any empirical or experimental methodology. In the present work, an improved multiscale model aimed at describing membrane fouling in the UltraFiltration (UF) process was proposed. The proteins-surface interactions were accurately computed by first-principle-based calculations. Both the effective surface of polysulfone (PSU) and the first layer of proteins adsorbed on the membrane surface were accurately modelled. At macroscopic scale, an unsteady-state mass transfer model was formulated to describe the behaviour of a typical dead-end UF process. The adsorption of an enzyme, i.e. the phosphotriesterase (PTE), on polysulfone (PSU) membrane surface was investigated as well through a double-scale computational approach. The results of such a formulated model were useful to obtain a detailed knowledge about enzyme adhesion and to give precise indications about the orientations of its binding site. One of the most important challenges is to use the stochastic approach adding an improved nano- and micro-scale step to the well-established multiscale procedure. The implementation of a Monte Carlo algorithm was performed with the aim of investigating the fouling structure during membrane operation like different micro-equilibrium states. The final aim of the work was to carry out the calculation of both Osmotic Pressure and Diffusion Coefficient in the fouling cake by the already-performed Monte Carlo simulations. Furthermore, the so-obtained parameters were exploited in macroscopic CFD simulations so as to calculate the overall resistance of the deposit accumulated on membrane surface during filtration.