Maria Cristina Annesini | Università degli Studi "La Sapienza" di Roma (original) (raw)

Papers by Maria Cristina Annesini

SOLARPACES 2019: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2020

The possibility of storing solar thermal energy to decouple electricity production from the avail... more The possibility of storing solar thermal energy to decouple electricity production from the availability of the solar resource is a key factor in development of concentrating solar power (CSP) technologies. In this context, a challenging perspective is the storage of solar energy on a seasonal basis through thermochemical storage (TCS) systems, as well as the use of excess summer solar energy for stabilizing the annual electricity production, thus increasing the capacity factor of the CSP plant. In this paper, we report the experimental characterization of a material initially developed within the context of CO2 capture technologies, namely calcium oxide supported on mayenite, which in previous investigations shown good sorption capacity and substantial cycling stability. The objective of this new experimental campaign is to test the performance of this material when adopted for thermochemical storage purposes. The tests confirmed that the material, synthesized through a SolGel method, remains stable over long term cycling, with a carbonation conversion higher than 80%. Furthermore, no physical/chemical interaction of the mayenite support with CO2 was observed, confirming its inertia and suitability for TCS purposes.

Mixing of a diffusing species entrained in a three-dimensional microfluidic flow-focusing cross-j... more Mixing of a diffusing species entrained in a three-dimensional microfluidic flow-focusing cross-junction is numerically investigated at low Reynolds numbers, 1≤Re≤1501≤Re≤150 , for a value of the Schmidt number representative of a small solute molecule in water, Sc=103Sc=103 . Accurate three-dimensional simulations of the steady-state incompressible Navier–Stokes equations confirm recent results reported in the literature highlighting the occurrence of different qualitative structures of the flow geometry, whose range of existence depends on Re and on the ratio, R, between the volumetric flowrates of the impinging currents. At low values of R and increasing Re, the flux tube enclosing the solute-rich stream undergoes a topological transition, from the classical flow-focused structure to a multi-branched shape. We here show that this transition causes a nonmonotonic behavior of mixing efficiency with Re at constant flow ratio. The increase in efficiency is the consequence of a progressive compression of the cross-sectional diffusional lengthscale, which provides the mechanism sustaining the transversal Fickian flux even when the Peclet number, Pe=ReScPe=ReSc , characterizing mass transport, becomes higher due to the increase in Re. The quantitative assessment of mixing efficiency at the considerably high values of the Peclet number considered ( 103≤Pe≤1.5×105103≤Pe≤1.5×105 ) is here made possible by a novel method of reconstruction of steady-state cross-sectional concentration maps from velocity-weighted ensemble statistics of noisy trajectories, which does away with the severe numerical diffusion shortcomings associated with classical Eulerian approaches to mass transport in complex 3d flows.

his paper presents an overview of recent research carried out by the authors on the development a... more his paper presents an overview of recent research carried out by the authors on the development and analysis of mathematical models describing hydrogen production in membrane reactors. The case considered is that of methane steam reforming (SR) in a reactor with the typical double pipe configuration, in which a hydrogen-permeable membrane is present on the outer wall of the innermost tube. The model developed accounts for the rate of reaction, convective and dispersive transport in the axial and radial directions, and hydrogen permeation across the membrane. Density variations with pressure and gas composition have been accounted for, leading to a full coupling of mass and momentum transport. Different geometric aspect ratios have also been studied to assess the influence of catalyst volume on the overall performance of the system. The presence of two distinct transport regimes, in which hydrogen permeation is limited either by transport within the packed bed or permeation across the membrane, has been identified, along with the operating conditions that determine their range of existence. This has allowed the development of a simplified model, valid under the hypothesis that the reaction is fast compared to transport. In the permeation-controlled regime, the permeate flow rate and recovery may be found by solving a set of two PDEs, whereas an analytical solution is available for the transport-controlled regime. The main steps and observations that have brought to the development of the simplified model are presented, along with a guide to its implementation.

The International journal of artificial organs

Adsorption equilibrium of bilirubin onto polymeric resins is studied. Solutions containing albumi... more Adsorption equilibrium of bilirubin onto polymeric resins is studied. Solutions containing albumin are used in order to simulate the behavior of systems for removal of albumin-bound substances from blood, serum or dialysis fluids. The effect of albumin pre-loading on the resin is also analysed. Results are explained by a chemically based model that accounts for binding reaction between albumin and bilirubin in the liquid phase. Thermodynamic equilibria and physical models are essential tools for designing adsorption columns aimed at detoxification treatments.

Hydrogen peroxide decomposition is analysed for its possible implementation in a gas accumulation... more Hydrogen peroxide decomposition is analysed for its possible implementation in a gas accumulation unit for the supply of a robotic actuation system. Reaction kinetics over MnO 2 powder catalyst were investigated and used for preliminary feasibility considerations. The results show that this process could be suitable for the considered application and its implementation is worth being further investigated.

Substituted phenols are extensively produced and utilized in chemical industry and therefore they... more Substituted phenols are extensively produced and utilized in chemical industry and therefore they are largely present in wastewater. In this paper we considered phenolic mixtures which are representative of industrial wastewater, usually containing multiple substrates. In these conditions, degradation process is strongly affected by the complex interactions among substrates, which include enhancement, inhibition and co-metabolism so a process model is an useful tool to explore and predict the process evolution. Objective of this work was to formulate a kinetic model for the biodegradation of binary mixtures performed in a sequencing batch reactor (SBR). Two model mixtures were investigated: a 4-nitrophenol (4NP) and 2,4-dimethylphenol (2,4DMP) mixture, and a more recalcitrant mixture of 4NP and 2,4-dichlorophenol (2,4DCP). Kinetic tests were performed at different feed concentrations, with single compounds and mixtures and each biodegradation process was kinetically characterized. H...

International Journal of Hydrogen Energy, 2015

Ethanol Modeling a b s t r a c t

Industrial & Engineering Chemistry Research, 2014

ABSTRACT The sodium manganese ferrite thermochemical cycle for hydrogen production by water split... more ABSTRACT The sodium manganese ferrite thermochemical cycle for hydrogen production by water splitting can successfully operate in a relatively low temperature range (1023–1073 K) and has a high potential for coupling with the solar source using conventional structural materials. With the aim of implementing the cycle in a solar reactor, the hydrogen evolution rate from the reactive mixture measured in laboratory apparatus has been modeled by using a shrinking-core model. Such a model proved to adequately describe the rate of hydrogen production in the studied temperature and water concentration range. The model was extended to predict the behavior of the reactive mixture subjected to different experimental conditions.

ABSTRACT In this paper we report the results of an investigation on the performance of convention... more ABSTRACT In this paper we report the results of an investigation on the performance of conventional and two phase partitioning bioreactors (TPPBs) operating in sequencing batch mode applied to the biodegradation of a binary mixture of 2 substituted phenols, 2,4-dimethylphenol and 4-nitrophenol. The TPPB was operated with the DuPont polymer Hytrel 8206 as the partitioning phase, which was demonstrated to be effective in the uptake and release of a variety of phenolic compounds. Partition tests were performed on both compounds, and partition coefficients of 201 and 143 were obtained in distilled water for 2,4-dimethylphenol and 4-nitrophenol, respectively. Parallel kinetic tests were carried out in conventional and TPPB bioreactors under the same operating conditions. The TPPB results showed a reduction in the aqueous phase concentration for both substrates to sub-inhibitory levels in all the tests, and the effect was more evident for 2,4 dimethylphenol as expected by the partition coefficient values. Moreover, the presence of the polymer has a marked effect on the process kinetics that are significantly increased for both substrates in comparison to the values of the conventional reactor.

Paracetamol is a widely used drug, accidental overdosing being particularly encountered in childr... more Paracetamol is a widely used drug, accidental overdosing being particularly encountered in children. The resulting acute liver failure is a therapeutic challenge. There is little agreement on the optimal therapy in paracetamol overdose. Gastric lavage, activated charcoal ingestion and N-acetylcysteine administration are usually effective just shortly after the poisoning, whereas the usefulness of high-flux haemodialysis and haemoperfusion is controversial. Recently, use of "liver dialysis" (or "albumin dialysis") showed promising results in the treatment of acute liver failure from various aethiologies. We describe a case of accidental paracetamol overdosing in a 4-year boy, admitted 4 days after the ingestion of 154 mg/ Kg body weight of paracetamol for four days. We treated him successfully with two sessions of albumin dialysis (MARS -"Molecular Adsorbent Recirculating System") for fulminant liver failure and grade III hepatic encephalopathy. After two sessions of MARS dialysis, the patients had a spectacular clinical recovery. The patient was discharged 12 days after admission with normal liver enzymes. Our case suggests that albumin dialysis may be feasible treatment option in acute liver failure due to paracetamol overdose.

2010 IEEE International Conference on Robotics and Automation, 2010

The need for novel, high performance actuators felt in several fields of robotics, such as assist... more The need for novel, high performance actuators felt in several fields of robotics, such as assistive or rehabilitative robotics, is not fully satisfied by current actuation means. This fosters an intense research on novel energy transduction methods. In particular, propellant-based chemical actuators, able to directly convert chemical energy into mechanical energy, appear very promising, although their potential in robotics has

Water Science & Technology, 2010

In this paper, a comparison is provided between liquid-liquid and liquid-solid partitioning syste... more In this paper, a comparison is provided between liquid-liquid and liquid-solid partitioning systems applied to the removal of high concentrations of 4-nitrophenol. The target compound is a typical representative of substituted phenols found in many industrial effluents while the biomass was a mixed culture operating as a conventional Sequencing Batch Reactor and acclimatized to 4-nitrophenol as the sole carbon source. Both two-phase systems showed enhanced performance relative to the conventional single phase bioreactor and may be suitable for industrial application. The best results were obtained with the polymer Hytrel which is characterized by higher partition capability in comparison to the immiscible liquid solvent (2-undecanone) and to the polymer Tone™. A model of the two systems was formulated and applied to evaluate the relative magnitudes of the reaction, mass transfer and diffusion characteristic times. Kinetic parameters for the Haldane equation, diffusivity and mass transfer coefficients have been evaluated by data fitting of batch tests for liquid-liquid and liquid-solid two phase systems. Finally, preliminary results showed the feasibility of polymer regeneration to facilitate polymer reuse by an extended contact time with the biomass.

Water Research, 2000

AbstractÐThe aqueous phase adsorption of methyl-tert-butyl ether (MTBE) and tert-butyl alcohol (T... more AbstractÐThe aqueous phase adsorption of methyl-tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) onto an Amberlite resin at 208C was investigated under dierent operating conditions. To this end, both batch and ®xed-bed experiments were performed on single solute and bisolute mixtures. The single-solute equilibrium data were ®tted by means of the Freundlich equation and isotherm parameters were determined. The data on bisolute adsorption showed a strong competitive eect between MTBE and TBA, which can be described by means of a theoretical model accounting for the non-ideal behaviour of adsorbed phase. Experimental breakthrough curves were determined for single-solute solutions in order to evaluate the overall mass transfer coecients between liquid and adsorbed phases. A predictive model for multisolute ®xed-bed adsorption is proposed and the theoretical results are compared with experimental data. 7

Water Research, 1987

The removal of organic species from aqueous solution by activated carbons is investigated. The la... more The removal of organic species from aqueous solution by activated carbons is investigated. The latter ones are prepared from olive husks and almond shells. A wide range of surface area values are obtained varying temperature and duration of both carbonization and activation steps. The adsorption isotherm of phenol, catechol and 2,6-dichlorophenol involving the activated carbons prepared are obtained at 25 degrees C. The corresponding behavior is quantitatively correlated using classical isotherm, whose parameters are estimated by fitting the equilibrium data. A two component isotherm (phenol/2,6-dichlorophenol) is determined in order to test activated carbon behavior during competitive adsorption.

Water Research, 1991

Evaporation and distillation processes have been often used to treat wastewater from olive oil mi... more Evaporation and distillation processes have been often used to treat wastewater from olive oil mill effluent: the effluent COD reduction varies widely with the characteristics of the waste. In this work we report some distillation tests on centrifuged olive oil mill effluent, performed in order to analyse the effect of storage time on the evaporation behaviour of this waste. Experimental data show that the ageing processes cause an increase in the concentrations of volatile compounds. According to a preliminary model such a behaviour can be described in terms of a chemical and a biochemical reaction between a few pseudo-compounds.

Transplantation Proceedings, 2009

Journal of Hazardous Materials, 2011

The biological treatment of phenolics is constrained by the inherent cytotoxicity of these compou... more The biological treatment of phenolics is constrained by the inherent cytotoxicity of these compounds. One method to alleviate such toxicity is to add a sequestering phase to absorb, and subsequently release, the substrate(s) to the micro-organisms; such a system is termed a Two Phase Partitioning Bioreactor. Here we have compared the performance of a TPPB, relative to single phase operation, in which a small volume (5%, v/v) of beads of the polymer Hytrel 8206 was used to treat aqueous mixtures of 2,4-dimethylphenol and 4-nitrophenol. Hytrel 8206 was selected from a range of polymers that were tested for their partition coefficients (PCs) for the target molecules, with the more hydrophobic compound (2,4-dimethylphenol) having a higher PC value (201) than 4-nitrophenol (143). Significantly increased removal rates for both substrates were demonstrated in TPPB mode relative to single phase operation. Additionally, the differential release of the compounds to the aqueous phase and their distinct PC values changed the kinetic pattern of the biotreatment system, smoothing out the cellular oxygen demand. Release of the substrates by the polymer over 60 operating cycles was virtually complete (>97%) demonstrating the reusability and robustness of the use of polymers in overcoming cytotoxicity of phenolic substrates.