The scientific paper by members of the Brazilian community on Materials research featured this month is: “Green” colloidal ZnS quantum dots/chitosan nano-photocatalysts for advanced oxidation processes: Study of the photodegradation of organic dye pollutants. Alexandra A.P. Mansur, Herman S. Mansur, Fábio P. Ramanery, Luiz Carlos Oliveira, Patterson P. Souza. Applied Catalysis B: Environmental, 158–159 (2014), 269–279. DOI:10.1016/j.apcatb.2014.04.026.
“Green” nanoparticles for water treatment
A group of researchers from Brazilian institutions developed nanoparticles that are triply “green”. They can be used to purify water, one the greatest global challenges of the 21st Century. In addition to that, they coexist harmonically with the environment and biological systems. Finally, they are produced by means of an eco-friendly process.
“We managed to integrate properties and characteristics rarely found in nanostructured systems, which are biocompatibility and environmental compatibility, using a ‘green’ process”, says Professor Herman Sander Mansur from the Federal University of Minas Gerais (UFMG).
The particles are formed by “quantum dots” (fluorescent semiconductor nanocrystals) of zinc sulfide (ZnS) with approximately 3.8 nm in size, coated with “shells” made of chitosan – an abundant, low-cost material, derived from the external skeleton of crustaceans such as shrimps and crabs. The synthesis process of these particles is completed in a single stage, carried out in an aqueous medium, without using toxic substances.
In a study performed by the research team, the nanoparticles displayed the capacity to degrade contaminant organic pigments usually found in water, using only light, including direct sunlight.
“The results were very promising, since we were able to observe that the system was effective for the photodegradation of organic contaminants found in the aqueous solutions we studied,” said Herman Mansur, who is the corresponding author of a paper about the research, recently released by the journal Applied Catalysis B: Environmental.
The research will also be the subject of a patent application, which the authors already started writing. “The following step will be searching potential partners in the private sector, in order to commercialize it as a product for cleaning waters which are polluted by organic pigments”, says Mansur.
History of the paper
It was during scientific discussions occurred in the monthly meetings of the Exact Sciences and Materials Board of the Minas Gerais State Research Foundation (FAPEMIG) that the initial idea for the research came up. In fact, both, Herman Mansur, coordinator of the UFMG Nanosciences, Nanotechnology and Innovation Center, and Luis Carlos de Oliveira, coordinator of the research group in Advanced Materials for Catalysis and Photocatalysis in the same university, were members of said advisory committee between February 2010 and the same month in 2014. According to Mansur, “the main idea was to use nanotechnology to develop innovative environmental solutions to clean up water, as it is an increasingly scarce resource in the world, whether in developed or emergent countries, as well as the ones with low social and economic development”.
Then, the professors prepared a project that combined the experience from the two research groups: Professor Mansur’s team, dedicated for twenty years to the development of nanomaterials and nanostructures by means of the synthesis of quantum dots, and Professor Oliveira’s group, which had been working in the field of chemical catalysis, searching sustainable solutions for the treatment of industrial waste.
Their initial research led to a first article on nanoparticles with cadmium sulfide (CdS) core and niobium oxide shell: L. C Oliveira et. al. One-pot Synthesis of CdS@Nb2O5 Core-Shell Nanostructures with Enhanced Photocatalytic Activity. Applied Catalysis. B, Environmental, v. 152:53, p. 403-412, 2014 (DOI:10.1016/j.apcatb.2014.01.025).
As a result, the group conceived, designed and developed an application for the concept of “green chemistry” in the whole project, producing zinc sulfide and chitosan particles, and their synthesis process. In the following stage, their research also incorporated the collaboration of Professor Patterson P. Souza, from the Federal Center for Technological Education of Minas Gerais (CEFET-MG), who conducted mass spectrometry tests, assessing the degradation of the organic pigments used as models for the polluting chemical species.