1,721,164 research outputs found
Effect of Pressure on the Electrochemical Conversion of CO2 to CO
Full text linkTo minimize the negative effect of carbon dioxide as a greenhouse gas and introduce renewable energy in the chemical and energy chain, an interesting approach is the Carbon Capture and Conversion. In this context, one of more appealing conversion strategies is the el
Ectrochemical reduction of CO2, which could combines the utilization of excess electric energy from intermittent renewable sources with CO2 (1). Furthermore, CO2 can be selectively converted into various useful chemicals by changing the operating conditions of electrolysis. In particular, an increasing attention has been devoted to the electrochemical conversion of carbon dioxide to carbon monoxide (2,3). The main obstacle of that conversion from water solution is the low CO2 solubility in water. In this work, a methodical study on the effect of the CO2 pressure and of other operating parameters on the conversion of CO2 at flat cathodes to carbon monoxide was performed. In detail, the reduction of CO2 was studied in different kind of electrochemical cells to evaluate the effect of various operating parameters, including the nature of the supporting electrolyte and the nature of cathode (Ag and Au), the current density, the pH and the pressure of CO2 . It was shown that an increase of the pressure
leads to an improvement the stability of the electrode
Conventional Reactors and Microreactors in Electro-Fenton
No full textThe cells used for electro-Fenton process look quite different, ranging from the simple open tanks, through the parallel-plate cells, to the sometimes complex designs with three-dimensional moving electrodes or microelectrodes. Recently, pressurized cells and microreactors have been used to improve the performance of the process. This chapter presents a general overview of the main cell configurations used in electro-Fenton process for the treatment of organic pollutants. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed
Electrochemical incineration of oxalic acid in the presence of NaCl
Full text linkRecent researches have demonstrated that electrochemical methods offer an attractive alternative to traditional routes for treating wastewaters containing toxic or/and refractory organic pollutants. The effectiveness of the electrochemical treatment depends on many factors including the presence in solution of specie able to act as mediators. In particular, the effect of chloride ions on the performances of the process has been the object of numerous researches. However, up to now, many practical and theoretical aspects about this argument are not completely clear. In the present work, the anodic incineration of oxalic acid (OA) in the presence of NaCl has been investigated with the aim of studying in a systematic way the influence of numerous parameters, such as the current density, the flow rate, the OA, the NaCl concentrations and the pH on the performances of the process and to individuate the optimal operative conditions. Oxalic acid was chosen as model substrate for its low reactivity toward anodic oxidation, which also results in an incomplete mineralization of more complex organics. Furthermore, the oxidation of this simple molecule does not involve the formation of stable intermediates thus giving rise to a more easy rationalizing of experimental results. Since the effect of NaCl on the process is expected to depend on the nature of the electrodic material, two very different anodes were used: the Ti/IrO2-Ta2O5 which presents a quite low oxygen overpotential and boron doped diamond (BDD) which is probably one of the more promising materials for the electrochemical incineration
Devolopment of a process for the treatment of synthetic wastewater without energy inputs using the salinity gradient of wastewaters and a reverse electrodialysis stack
No full textElectrochemical processes are considered very effective methods for the treatment of wastewater contaminated by organics resistant to conventional biological processes and various inorganic pollutants. Large sites that treat wastewaters usually deal with a large number of waters often characterized by different salinity contents, that could be potentially used to provide the energy necessary for the electrochemical remediation. Hence, in this work a reverse electrodialysis (RED) process for the treatment of synthetic wastewaters contaminated by organics, without energy inputs, using the salinity gradient of different wastewaters, was studied, for the first time. It was found that two synthetic wastewaters with different NaCl content can be effectively used in a RED system to drive anodic and cathodic processes for the removal of their organic contents without external energy supplies. The effects of salinity gradient, external resistance and set-up of the process was evaluated. Under optimized operating conditions, a fast and high removal of TOC (about 70% every hour) in the anodic compartment and a good stability of operating conditions for all the monitored time (10 h) were achieved. In addition, about 67% of the solution with high salinity used in the stack to provide the salinity gradient was effectively treated in the anodic compartment of the stack
ELECTROCHEMICAL PROCESSES FOR THE TREATMENT OF CHLORINATED ALIPHATIC HYDROCARBONS IN WATER SOLUTIONS
No full textElectrochemical conversion of carbon dioxide: effect of the cell and of the operating parameters on the performances of the process.
Full text linkRecycling technologies of CO2 allow to introduce renewable energy in the chemical and energy chain, storing a renewable energy in the chemical form. In this context, electrochemical conversion of CO2 is considered one of the more interesting approaches, using excess electric energy from intermittent renewable sources. (1) Furthermore, products can be selectively controlled by changing the operating conditions of electrolysis. In particular, in the last years, an increasing attention has been devoted to the electrochemical conversion of CO2 to formic acid or formate in water. (2,3,4) The main hurdle of the reduction of CO2 from water solution is the low CO2 solubility in water. In this work, a systematic study on the effect of the CO2 pressure and of other operating parameters on the conversion of CO2 at tin flat cathodes to formic acid was performed to overcome this obstacle. The reduction of CO2 was first studied in a glass undivided cell at atmospheric pressure to evaluate the effect of various operating parameters, including the nature of the anode and of the supporting electrolyte, the mixing rate, the current density and cathode to anode area ratio. Subsequently, in order to improve the performance of the process, a series of electrolysis was performed in a batch stainless steel undivided cell in a wide range of pressure of CO2 and current density. It was shown that an increase of the pressure leads to a drastic enhancement of the final formic acid concentration. Indeed, the utilization of relatively high CO2 pressures (15–30 bar) allowed to achieve high concentrations of formic acid (up to 0.46 mol L-1) at high current density (up to 90 mA cm-2) and with cheap and simple undivided cell. (5) Several researchers have discussed the economic feasibility for large-scale design of the CO2mitigation electrochemistry system, by suggesting that could be operationally profitable. Therefore, in the last stage, the process was performed in a pressurized filter-press cell, suitable for scale-up on applicative scale. The goal of this research is to provide an electrochemical process sustainable at applicative point of view characterized by a high yield and selectivity of the product. Long-term stability has also to be acquired in order to obtain an interesting alternative at commercial level for the conversion of carbon dioxide
Conversion of CO2 to formic acid in a microfluidic electrochemical cell with and without supporting electrolyte
Full text linkElectrochemical reduction of carbon dioxide to formic acid or formate (FA) is considered an interesting route to
valorize CO2 effluents. Here, we have performed the conversion of CO2 to FA in an undivided microchannel
electrochemical reactor characterized by very small inter-electrode distances (75–250 μm) using Na2SO4 as
supporting electrolyte (SE). It was found that the use of the microfluidic cell allows to work both in the presence
and in the absence of SE with lower cell potentials with respect to conventional cells and to obtain significant
conversions per pass of CO2 to FA. The effect of many parameters, such as distance between electrodes, flow rate,
current density, concentration of Na2SO4 and pH, was studied. In particular, it was shown that the production of
FA increases by reducing the concentrations of Na2SO4 and it presents the maximum value in the absence of it
Carbonization of waste organic matrices in zinc-based molten salts
No full textMolten salt driven catalytic carbonisation offers a new and emerging technology approach for treating organic wastes to achieve negative CO2 emissions and a circular
carbon economy by converting the low-value carbon content of the waste into high value solid carbon materials which can be reused, and also converting the hydrogen content of the waste into a low-carbon hydrogen-rich fuel gas. In the work herein, a methodology to handle pure ZnCl2 (and load it into batch reactors) was built. The ZnCl2 used to this purpose was provided by VWR Chemicals (>97% of purity). Pellets of HDPE were provided by polymer testing laboratory. After that, some experimental trials on molten salts assisted pyrolysis using ZnCl2 in mixture with HDPE were conducted. Then the HDPE pellets were milled to obtain filaments with dimensions of 1mm x 2mm. The preliminary collected outcomes showed that, when the reaction temperature increased from 300 to 380 °C for 30 min, the gaseous products yield increased from values below 1%w/w to 3%w/w. In both experiments hydrogen was the main component (90 % mol). With an increase of the reaction time from 30 min to 3 h an enhancement in the production of light olefins in the place of hydrogen was observed. TGA analyses were conducted of ZnCl2, of HDPE and of HDPE in the presence of ZnCl2 and the catalytic activity of ZnCl2 was demonstrated by an improvement of the mass loss rate
Electrochemical production and use of chlorinated oxidants for the treatment of wastewater contaminated by organic pollutants and disinfection
Full text linkIn the last years, an increasing attention has been devoted to the use of electrogenerated chlorinated oxidants for the treatment of wastewater polluted by recalcitrant organics and/or for the disinfection of water contaminated by pathogen microorganisms. In this review, more recent and relevant findings were presented and critically discussed. The main advantages and disadvantages of this technique were commented, including the potential formation of toxic chlorinated organic specie and of chlorate and perchlorate or the difficult selection of proper operative parameters, as well as the key points that should be addressed to enhance the use on an applicative scale
Il mentoring nella docenza universitaria: il progetto “Mentori per la didattica” nell’Università di Palermo
Full text linkLa qualificazione delle competenze didattiche del docente universitario è oggi un obiettivo importante perseguito dalle istituzioni accademiche per innovare la didattica (Sursock, 2015; Gaebel & Zhang, 2018; QUARC_Docente, 2017). Le metodologie indicate dalla ricerca sollecitano l’adozione di strategie di formazione in grado di attivare l’implicazione attiva, lo scambio reciproco, la condivisione di valori e di pratiche di insegnamento apprendimento, nella logica di una comunità che apprende (Cox, 2004). In tale contesto, il mentoring si colloca come un’esperienza particolarmente significativa per il miglioramento dell’azione professionale del docente in campo didattico e la socializzazione organizzativa (Underhill, 2006; Johnson, 2015). L’attività di mentoring fa leva su interventi di guida e aiuto al miglioramento (Sorcinelli & Yun, 2015) ma esistono in letteratura diversi modelli con forme organizzative e relazionali specifiche. Il progetto “Mentori per la didattica”, realizzato nell’ateneo di Palermo, si connota come azione di peer mentoring sviluppata dai docenti in termini di supporto reciproco fra mentori e mentee. L’esperienza si sviluppa all’interno di una comunità che indaga, riflette ed elabora, in un percorso di ricerca per il miglioramento continu
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