Authors: Olga Ferreira*, João Gomes, Maria J. Calhorda, Elisabete R. Silva*
Over two-thirds of Earth’s surface is covered by water, and its contamination with invasive aquatic organisms (biofouling on submerged surfaces) is an actual challenge. This bioburden, conventionally treated with the release of toxic agents into the surroundings of the contaminated surfaces, is associated with serious environmental and economic penalties, as well as health risks on several industrial applications (e.g. water purification, desalination units).
In this work, it was developed a new non-toxic alternative able to control this biofouling, by applying a novel immobilisation process (WO2016/093719 A1, 2016) for antifouling agents. Briefly, the immobilisation of biocidal agents (e.g. Econea) was performed by providing new functional biocides (e. g. Econea-NCO) capable of being tethered in polymeric coatings.
Bioactivity assessment of the developed antifouling systems suggested that the biocide properties were not significantly affected by the functionalization process. Econea biocide and its functional counterpart showed similar bioactivity against Staphylococcus. aureus, and similar Minimal Inhibitory Concentration (MIC).
Antifouling assessment of coated polymeric substrates with the most promising coatings (silicone marine based paint) containing the immobilized biocide, was carried out at near static conditions in Atlantic seawater (real field test) and in an artificial seawater aquarium. Auspicious antifouling performances were obtained. The coated substrates remained clean after being immersed in those aquatic environments for more than a year.
Furthermore, an ecotoxicity study of biocidal coatings following standards included in the EU hazard assessment of substances and European Eco-label was performed. In accordance with the European standards the coatings were classified as not harmful to the environment.
Structured filters supports (e.g. monoliths) were also successful coated with the best biocidal coatings. Uniform polymeric films were obtained, and adhesion tests are on-going. The next step of this work is to develop an experimental method to confirm the effectiveness of the coated supported filter structures against biofouling at simulated operational conditions (e.g. water circuits). This approach is presented as an alternative non-toxic and long-lasting antifouling strategy.
Support for this work was provided by FCT through UID/MULTI/00612/2013 and Pest-OE/QUI/UI0612/2013. O. Ferreira and Dr. E. R. Silva are also grateful for the financial support from FCT, PhD Grant PD/BD/128370/2017 and Post-Doc fellowship SFRH/BPD/88135/2012, respectively. The authors also thank the support of HEMPEL A/S and P. Rijo for the work collaboration.