Shipping: an environmentally friendly end to barnacle build-up?
It only takes a few months for an underwater boat hull to become completely covered and overgrown with organisms such as barnacles, bacteria and algae, and fighting this phenomenon, known as marine fouling, is a constant battle with heavy costs for both the environment and industry.
Now, a team of EU-funded scientists has made a discovery that could lead to a more environmentally friendly method of tackling the problem.
The team, made up of researchers based in Germany and the Netherlands, carried out experiments that showed steel plates that had been coated in vanadium pentoxide nanoparticles could be exposed to seawater for weeks without deposits of barnacles, bacteria and algae forming. In contrast, plates that were coated with the ship's normal paint exhibited massive accumulation of these unwanted materials after exposure to seawater for the same period of time.
As these tiny vanadium pentoxide nanoparticles can inhibit the growth of barnacles, bacteria and algae on surfaces in contact with water, this finding, presented in the journal Nature, could lead to the development of new protective, antifouling coatings and paints for ship hulls, sea buoys and offshore platforms.
To boot, as well as being more effective, these nanoparticle-based coatings would be much less damaging to the environment than the ship coatings currently used.
The project was supported in part by the BIOMINTEC ('Biomineralization: understanding of basic mechanisms for the design of novel strategies in nanobiotechnology') project, which was fully funded by a Marie Curie 'Networks for Initial Training' (ITN) grant to the tune of EUR 2,300,000.
Marine fouling is a costly problem as the build up of organisms such as algae, mussels and barnacles increases the objects' water resistance and, in turn, its fuel consumption. Increased fuel consumption means more CO2 emissions as well as more costs for shipping companies.
Although this effect can be to an extent counteracted with antifouling paints, conventional biocides are less effective and can have adverse environmental consequences. In addition, microorganisms are able to develop resistance to them.
On arriving at their discovery, the scientists took inspiration from one of nature's own defence mechanisms: certain enzymes found in brown and red algae produce halogen compounds that are synthesised by the algae to protect them against microbial attack and predators.
With this process in mind, the team set out to effectively imitate it using the vanadium pentoxide nanoparticles.
Vanadium pentoxide functions as a catalyst so that hydrogen peroxide and bromide combine to form small quantities of hypobromous acid, which is highly toxic to many microorganisms and has a pronounced antibacterial effect. The required reactants are present in seawater: this already contains bromide ions, while small quantities of hydrogen peroxide are formed when it is exposed to sunlight.
As part of this study, research was also carried out using a highly sensitive inductively coupled plasma mass spectrometer (ICP-MS) to determine the concentration of vanadium in various samples of seawater that had been exposed to the coated material for different lengths of time. The results showed that levels were only slightly elevated above the normal average vanadium concentration in seawater. This means that as only very tiny amounts of vanadium migrate from the coating into seawater it has no negative impact on the environment.
Lead study author Wolfgang Tremel from Johannes Gutenberg University Mainz (JGU) in Germany comments: 'Vanadium pentoxide nanoparticles, due to their poor solubility and the fact that they are embedded in the coating, are considerably less toxic to marine life than are the tin- and copper-based active substances used in the commercially available products. Here we have an environmentally-compatible component for a new generation of antifouling paints that employ the natural defence mechanism used by marine organisms.'
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Document Reference: Natalio, F., et al. 'Vanadium pentoxide nanoparticles mimic vanadium haloperoxidases and thwart biofilm formation', Nature Nanotechnology, 2012. doi:10.1038/NNANO.2012.91
Subject Index: Coordination, Cooperation; Environmental Protection; Industrial Manufacture; Innovation, Technology Transfer; Nanotechnology and Nanosciences; Scientific Research; Resources of the Sea, Fisheries; Social Aspects