Scientists Use Recycled CDs to Treat Wastewater

If you are one of those people, who have a huge stash of old CDs and have no idea what to do with them, then you might consider donating them for a good cause to the team of scientists at National Taiwan University.

The researchers engineered a device that makes use of the optical disks to break down organic pollutants in sewage waste and purify water.

The new invention, developed by Din Ping Tsai, a physicist at the National Taiwan University, and his team, will be presented at the Annual meeting of the Optical Society, which will be held between 6th and 10th of October in Orlando. There, the scientists are not only going to demonstrate a method of cheap, fast and efficient treatment of contaminated water, but they will also show how making use of unwanted old CDs can aid waste reduction.

In a nutshell, the large surface area of the disks is used to facilitate the growth of miniature semiconducting zinc oxide nanorods, which work as a photocatalysts and  break down organic molecules in water, when exposed to UV light.

The durability of the disks, and the fact that they can rotate at a very high speed, allow water to spread evenly when it drips onto the surface, and UV light can penetrate much easier to break down the pollutants much faster and more effectively.

The scientists explored this further to develop the water treatment device. Zinc oxide coated disks, a UV light source and a system for recirculating the water was all that the team needed. After putting all components of the so-called “spinning disk reactor” together, the team tested their invention using methyl orange dye, dissolved in water. After only an hour, the team noted that 95% of the contaminant was broken down.

The reactor can clean 150ml of water per minute, making it more efficient than any one of the already established photocatalytic wastewater treatment methods. Because it uses very little power and it is relatively small, the scientists claim that it can be easily used on small domestic sewage plants and treat water from urban runoff or farm waste.

The scientists, however, will not stop here. They are now keen to improve the efficiency of the device even further, and test whether they can improve on the speed by stacking disks to create multiple layers.