Latin America. Conicet researchers tested the effect of zinc oxide against fungi and bacteria in an indoor coating.
Functional paints with antimicrobial activity aim to control the growth of biofilms in indoor environments, especially hospitals and homes. From the economic point of view, paints represent the most convenient means for the protection of structural materials.
This is what the Argentine researchers Natalia Belloti, Guillermo P. López and María V. Gallegos refer to in the summary of their study "Use of recovered zinc oxide (ZnO) from depleted alkaline batteries in the formulation of bioactive paints".
"The challenges are many, because we must ensure that the compounds that are incorporated into the product retain their action to prevent or inhibit the growth of these agents, and also maintain it over time. They must also be environmentally friendly and economically viable," explains Natalia Belloti, a researcher at the National Council for Scientific and Technical Research (Conicet).
The also responsible for the Antimicrobial Coatings Area of the Center for Research and Development in Paint Technology (Cideprint, Conicet-UNLP-CICPBA), who works on the development of functional paints that contribute to the control of the presence of colonies of microorganisms harmful to health on walls and other surfaces, saw with her team that zinc oxide (ZnO) extracted from depleted batteries met all these qualities.
"It is a relatively new inorganic compound that has been studied a lot in recent times thanks to its versatility and its chemical, electronic, and optical properties. Particularly, we approach it for its antimicrobial quality and we look for a technological application, in this case as a component of wall paints, "says María Victoria Gallegos, Conicet researcher at the Center for Research and Development in Applied Sciences "Dr. Jorge J. Ronco".
"Once the battery is disassembled, we take a part called anode and wash it with distilled water, dry it and treat it with sulfuric acid, a procedure that results in a solution with dissolved zinc ions, which are the ones that interest us because from them we produce ZnO," says Gallegos, in charge of the recovery of metals from depleted alkaline batteries.
Closing a cycle
"The initial idea was to close a cycle: you have a waste, something that is not used and that contaminates; you use it to generate a new material that at the same time serves to solve another environmental and health problem, "adds Gallegos, and reports that, according to the numbers provided by the Multipurpose Pilot Plant (PlaPiMu-LASEISIC, CICPBA), where the manual disassembly of the batteries is carried out, every month about 80 kilos of these devices are treated, volume equivalent to the consumption of 8,000 inhabitants.
For his part, Guillermo López, Conicet fellow at Cideprint, points out that in the synthesis process to obtain the material of interest they used different precipitants, which are chemicals that help the formation of that solid.
"We tested three zinc oxides: one synthesized with sodium carbonate, another with oxalic acid, and the last of commercial origin. Then we go on to verify the antimicrobial action of each of them, "he says about the properties of the compound obtained. Finally, the one obtained with sodium carbonate was the most effective.
Bellotti highlights that fungi and bacteria are the most important agents from the health point of view of indoor coatings and "it is a trend that was accentuated after the pandemic and the permanence of people in closed places."
The Argentine researcher, like the rest of her colleagues who worked on this research, concludes that "both for paint films and for human health, the most harmful are fungi, which due to their invasive growth cause not only aesthetic damage on the surface, but also in the material at the physicochemical level".
Finally, it warns that "its proliferation generates bioaerosols and the release of a large number of spores into the environment", whose prolonged exposure is directly related to problems in the respiratory tract.
