Foto del docente

Giovanni Camera Roda

Alma Mater Honorary Professor

Alma Mater Studiorum - Università di Bologna

Adjunct professor

Department of Civil, Chemical, Environmental, and Materials Engineering

Research

Keywords: Process intensification Integrated process Kinetic analysis of photocatalytic reactions Photocatalysis Mathematical model In situ vitrification Photocatalytic ozonation Transport of radiant energy

The scientific activity deals with the analisys of some aspects of the process industry. The approach to the problems is both experimental by reproducing the investigated processes in laboratories and theoretical by developing and solving the relevant mathematical models.

With this respect some different numerical methods have been investigated that can be effectively applied to the solution of the sets of governing equations for the transport of mass, momentum, radiant energy and heat.

Many results have been applied for the industrial applications of the investigated processes.

The main themes of research can be categorized as follows:  

  • Engineering of photochemical and photocatalytic reactors.
  • Radiant energy transfer in participating, non reacting, still or moving fluids.
  • Modeling of some production processes in the microelectronics industry.
  • Solvent diffusion in a polymeric matrix.
  • Transport phenomena in membrane processes (pervaporation and dialysis).
  • In situ vetrification of highly polluted soils.
  • Process intensification by integration of different processes.
  • Green photocatalytic synthesis of fine chemicals.
  • Advanced oxidation processes for water treatment in various fields such as recirculating aquaculture systems.
  • Photocatalytic ozonation with control of the formation of bromate.

 



The Advanced Oxidation Processes (AOP) are an extremely interesting technology with future present applications in the detoxification of aqueous and gaseous streams and future possible applications for the industrial production of some important chemicals. The utilization of AOP in this field can be advantageous under many aspects, such as: the convenience of carrying out the reactions under safe and mild conditions (e.g. low temperature, atmospheric pressure, without chemical additives except the photocatalyst, which is typically a non toxic material) and the possibility of utilizing, as an energy source for the activation of the reaction, the largely available and free solar radiation. However, even if several practical applications of the AOP have appeared in the last years for the degradation of recalcitrant organic pollutants from aqueous or gaseous streams, the research in the field of chemical reactions for the production of chemical compounds of industrial importance is still at the beginning and many problems have to be studied and solved. In particular it would be necessary to attain satisfactory values of the yield of the process in order to make these technologies competitive and to scale up from the laboratory results to the industrial production.

In recent times, the interest has grown strongly towards the use of photocatalytic materials for the detoxification and the abatement of pollutant in gas phase and liquid phase inside specific apparatuses or by "functionalizing" some materials that are commonly exposed to the solar radiation during their ordinary utilization. In the latter case the attracting idea is to use innovative materials showing photocatalytic activity for buildings, covering, varnishes, clothes, wallpapers, carpets, window glasses etc. In this way the photocatalytic properties of the materials can be utilized to directly eliminate the polluting or toxic substances (e.g. the chemicals responsible of the well known "sick building syndrome") and also many pathogenic or spoiling agents from the surrounding environment in contact with these active (when lighted) surfaces. This application appears extremely intersting, it is virtually without drawbacks and can lead to substantial improvements of the "quality of life" at home or at work. However, from a practical perspective, both the activity of these materials and the way they are utilized (that is the process) should be improved.

Therefore the research deals with the optimization of the process with particular attention towards the "effective" utilization of both the photocatalyst in the reactor and of the impinging radiation. This study will give also important indications on the characteristics that the catalytic materials should have to meet this goal.

To this aim, different types of reactors are studied and tested and their design is enhanced according to the mathematical model of the process which considers the different phenomena taking place inside the reactor. In particular the study takes into account the kinetics of the reaction (which must be assessed and is in general a function of the local concentration of the reagents and of the intensity of the radiation) and hence the distribution inside the reactor of the reagents, of the photocatalyst and of the radiation. In fact, if just one of these factors (photocatalyst, light and reagent) is locally lacking, the reaction does not take place in that point with a consequent, significant, decrease of the yield.

The basis of the design and analysis of the photocatalytic reactors is the knowledge of the reaction kinetics. To this aim new guidelines have been drawn for the assessment of the kinetic law of "slurry" photocatalytic reactions with the evaluation of the relevant kinetic parameters and the calculation of the rate of photon absorption.

In order to enhance the rate of conversion and the yield of the reaction it is possible to couple a separation process to the photocatalytic process. In fact it has been demonstrated that the coupling of reaction and separation in an "integrated process" gives an increase of the yield.

A different research deals with the development of a prototype of an ISV (In Situ Vitrification)  plant. The ISV process is a thermal process based on the Joule effect aimed at the reclamation of polluted soils. It combines the high temperature (around 2000 °C) treatment of noxious waste with the possibility of  immobilizing it into a glass matrix, which is produced by the cooling of treated soil mass. An example of a successful application of the ISV process is the treatment of asbestos.

Compared with other vitrification technology, the ISV permits the treatment of "in-situ" polluted soils. So a mobile power supply equipped with a system for the abatment of the possible pollutant gaseous compounds has been designed to this aim. Experimental results concerning pre-pilot and real-scale tests have been analyzed by a mathematical model of the process which takes into account the energy transfer in the soil. In this way it has been possible to correlate the behavior of the non-linear electrical load with the properties of the soil which undergoes the melting process. In particular, the tests performed permitted to identify three distinct phases of the process namely a primer, an unstable and a stable phases. The non-linear behavior of the electrical conductivity of the melted mass has been explained by the model. The energy effectiveness of the process has been largely enhanced by appropriately reducing the radiative losses from the soil melt at very high temperature.

The "green" synthesis of fine chemicals, such as aromatic aldehydes, represents a new original field of research, with important possible industrial applications. The synthesis is carried out by coupling a membrane process (pervaporation) with photocatalysis. The synergistic mechanisms which act in the integrated process to get a process intensification  have been identified and discussed. The results show that, through an optimization of the integrated process,  a substantial increase of the conversion, of the selectivity and of the yield are obtained. Furthermore it has been demonstrated that additional positive features make this process sustainable and eco-friendly.

The "photocatalytic ozonation" is another integrated process which has been deeply investigated, since the coupling between ozonation and photocatalysis produces some very interesting results: a significant enhancement of the yield of purification and sterilization and an effective control of the formation of undesired byproducts such as bromate and other brominated compounds. Therefore, photocatalytic ozonation is very promising for practical applications in several water treatments. For instance, the characteristics of photocatalytic ozonation appear particularly interesting for the waters of swimming pools  and of both freshwater and seawater recirculating aquaculture systems.The parameters that affect the performances of this process have been studied and optimized.