Volcanic spring water helps make plastic electronics

When you think about how electronic components are made, water probably isn’t at the top of your raw material list. However, in a recently published study Journal of Water Chemistry and TechnologyResearchers from the University of Tsukuba used volcanic spring water to make the plastic that is an integral part of many modern technologies.

Plastic fixes the electronic components of many modern technologies. Polyaniline (PANI) is one such plastic. There are obvious advantages to making it in the most environmentally sustainable solvent, as millions of square meters of PANI are used for these and other purposes each year. Many solvents can be used to make PANI, but many of them are highly toxic and incompatible with traditional manufacturing processes for mass-produced devices such as inkjet printing.

One of the options for solvent is ethanol. In fact, this is what the authors of this study achieved. “We recently reported that ethanol with a small amount of iodine was used to produce polyaniline,” says senior author Professor Hiromasa Goto. “With all that said, water is the best eco-friendly solvent, so it would be an even better option.”

Pure water is useless as an acid and an oxidizing agent are often required to convert aniline to PANI. However, water from a volcanic source contains sulfate and large amounts of mineral ions, which in principle are sufficient for polymerization. This is the hypothesis that the researchers decided to test.

The researchers prepared PANI, PANI nanoparticles, and PANI/silk composites by mixing their mixtures at 0°C overnight. They optimized the conductivity of PANI and confirmed that trace elements are not the source of conductivity. “Scanning electron microscopy shows that each strand of the silk fabric produced is coated with PANI and the shape of the fibers does not change,” explains Professor Goto. “That’s why we developed a simple way to make textiles that can conduct electricity.”

Many other applications of these PANI composites are possible. For example, the researchers used filter paper impregnated with PANI to remove almost 75% of trace iodine from a water sample.

In this study, it was possible to prepare PANI using probably one of the most environmentally sustainable means: in low-temperature volcanic spring water. In order for water from any source to be a viable solvent for PANI synthesis, it will be easy to determine the optimum mineral concentration, pH and sulfate concentration for this synthesis. By synthesizing PANI in a way that does not produce oily waste and poses a fire hazard, its production for electronics can be considered the essence of green chemistry.