New Photocatalyst Particle Quickly Purifies Water

Aug 6, 2013
Masaru Yoshida, Nikkei Monozukuri
The new photocatalyst dispersed in water (left) and a comparison of arsenic reaction speed (right)
The new photocatalyst dispersed in water (left) and a comparison of arsenic reaction speed (right)
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Panasonic Corp developed a water clarification technology that detoxifies contaminants by dispersing a new photocatalyst particle in water.

It enables to quickly detoxify persistent organic pollutants (POPs) and poisonous metals contained in groundwater, etc, such as arsenic and hexavalent chromium. Panasonic expects to apply the technology to small-scale independent water purification equipment using solar light.

The new photocatalyst particle is made by bonding titanium dioxide fine powder that functions as a photocatalyst on the surface of a zeolite particle whose diameter is several micrometers. Because Coulomb force, an electrostatic attraction force that works among certain particles, is used as a bonding force, there is no need for chemical materials such as bonding agent.

As a result, the photocatalytic activity of the titanium dioxide on the surface of the zeolite particle does not deteriorate.

When a solution containing the new photocatalyst particles is churned, the titanium dioxide fine powder spreads in the solution and functions as a catalyst. The surface area of the titanium dioxide becomes large when it is dispersed in water.

As a result, it becomes possible to process persistent organic pollutants 100 times faster and arsenic 50 times faster, compared with fixed photocatalysts, which are made by forming a titanium dioxide thin film on the surface of a tile or glass fiber, Panasonic said.

Moreover, the new photocatalyst particle can be easily collected after being used. The reason why the titanium dioxide fine powder is dispersed by churning the solution is that it is weakly bonded to the surface of the zeolite. When the churning is stopped, the titanium dioxide begins to be bonded to the zeolite particles again and deposited on the bottom of a case as the original photocatalyst particles. And they can be easily separated from the water.

The only energy source required for the process is the ultraviolet light of sunlight, realizing a low cost and zero environmental load. In addition, because sedimentation is easy, the photocatalyst particle can be easily reused.

Existing water purification equipment using chlorination or reverse osmosis filter cannot remove poisonous metals such as arsenic enough. And water clarification using a fixed photocatalyst limits the contact area that reacts with harmful substances, slowing reaction speed.

Though a water clarification method that disperses photocatalyst powder in water is being proposed, it requires a large-scale treatment tank for separating and reclaiming the photocatalyst in water.

Panasonic plans to test the effect of a water clarification system using the new photocatalyst particle in a project with Jadavpur University, India, from October 2013.