Microalgal based applications for wastewater treatment have been and continues to be subject of attention by the scientific community. In literature many different microalgae are reported to be able to degrade wide groups of emerging pollutants (Eps) through their metabolism. However, the microalgal biomass valorization to develop technological and sustainable solutions for wastewater treatment are rarer. The synthesis of Carbon Encapsulated nanoparticles of zerovalent iron (CE-nZVI), which is part of the PerFORM WATER 2030, fits into this context.
Microalgae are eukaryotic photosynthetic organisms: they transform solar energy and inorganic compounds into new biomass and oxygen.
They are very versatile as they can be found both in fresh and marine water. Their size can range from a few to a few hundred micrometers and they can live as a single and independent cell or be organized in chains or in groups to form colonies.
Carbon Encapsulated zerovalent iron nanoparticles (CE-nZVI) represent a new promising solution for wastewater treatment. They constitute a nanomaterial based on a carbon shell that envelopes an inner core of iron oxides and metallic iron. The combination of these components gives to the nanoparticles a high sorbent capacity as well as reducing power. The presence of the zerovalent iron core also gives magnetic properties, allowing an easy recovery of the CE-nZVI after their use.
Within PerFORM WATER 2030, the synthesis of Carbon Encapsulated zerovalent iron nanoparticles (CE-nZVI) is performed at laboratory scale through hydrothermal carbonization. It is a thermochemical process occurring under moderate temperature and pressure conditions (T=180-250 °C e P= 10-35 bar) used to convert an organic compound into a structured carbon-based material.
Microalgae grown at pilot scale at Bresso WWTP are used as carbon source for the synthesis of CE-nZVI.
The microalgal biomass characteristics, like the presence of phenolic compounds, provide the reducing power needed to reduce the iron without the addition of any other chemical. The wet biomass and the iron, under the above described operative conditions, are subjected to different chemical reactions: micro and nanospheres of carbon are formed and the iron is trapped inside them.
The project includes the identification of the best synthesis conditions to produce the nanoparticles, the characterization of the best prototypes and the application in the removal of emerging pollutants and heavy metals from water solutions at laboratory scale.
Nanotechnology are on the rise in very different applications. This growing interest has also affected wastewater treatment.
Zerovalent iron nanoparticles are an already known technology. However, in the last years the focus has been put on the modification of these nanomaterials to improve their physico-chemical properties and their efficiency in wastewater treatment. As a matter of fact, carbon encapsulation is not a recurrent option for nZVI treatments.
The most similar applications that can be reported are the production of CE-nZVI at laboratory scale starting from the olive mill wastewater in Spain (Calderon et al. 2018) and the production of an iron improved biochar from blue-green microalgae in China (Peng et al. 2014).
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