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    Energising batteries with polluting blue dye

    Researchers at the University at Buffalo (UB) are exploring the possibility of using an industrial pollutant found in wastewater from textile mills to store energy.

    The chemical, a sapphire-coloured dye called methylene blue is a common ingredient in wastewater from textile production processes. A widely used dye, methylene blue is harmful to health and the wastewater needs to be treated before it’s released into the environment.

    However, scientists at the university believe it may be possible to give this industrial pollutant a second lease of life; when dissolved in water, the dye can be used to store and release energy on cue. This makes it ideal for redox flow batteries — large, rechargeable liquid-based batteries that could be used to store energy generated by renewable sources such as wind farms and solar power systems.

    Lead researcher Timothy Cook, assistant professor of chemistry in the UB College of Arts and Sciences, explains that current methods to sequester methylene blue out of water are expensive and generate other kinds of waste products.

    Anjula Kosswattaarachchi, a UB PhD student in chemistry and first author of the study added that finding a new way to use the blue dye-containing wastewater instead of cleaning it up, was the real motivation behind this project.

    Cook and his team are looking into the possibility of repurposing the wastewater itself while avoiding the costly process of extracting the dye from the water.

    The wastewater from textile making contains salt, which makes it ideal for a redox flow battery.            

    Initial trials show great promise with the battery charged and drained 50 times. Though efficient to begin with, the battery’s capacity for storing energy fell as molecules of methylene blue became trapped on a membrane critical to the device’s proper function.

    This problem has already been resolved now with a new membrane material used in the second battery. While maintaining the near-perfect efficiency of the first model, the second battery didn’t display any notable drop in energy storage capacity over 12 cycles of charging and discharging.

    The results mean that methylene blue is a viable material for liquid batteries.

    The next step in the research is to obtain real wastewater from a textile mill that uses the dye, evaporate it into a more concentrated solution containing the methylene blue and the salts, and test it directly in a battery. The technology also presents an alternative for wastewater management.

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