An inexpensive filter to remove Lead from tap water

Many homes, still receive drinking water through Lead-containing pipes. If the water's chemistry isn't ideal, or it flows quickly because of high demand, then pipes can corrode. When the corroding material contains Lead, the toxic metal dissolves or flakes off into the water, contaminating it with a dark discoloration and sometimes visible particles.

A team report a solution to the problem of Lead contamination in drinking water—an inexpensive faucet attachment that removes this toxic metal. Unlike conventional filters currently on the market, theirs includes a cartridge made with biodegradable plastic and indicates when it's "used up" by turning the tap water yellow.

They filed the cartridges with a mixture of Calcium phosphate and Potassium Iodide powder.

Calcium phosphate first binds with dissolved Lead in water to form Lead phosphate and free Calcium. The Calcium, which is harmless, ends up in the water, and the Lead phosphate stays in the filter. Lead phosphate, which is an inert solid, is trapped inside the filter by a nylon screen on the bottom of the unit. Once the reaction capacity of the Calcium

phosphate is reached, dissolved Lead reacts with potassium iodide, which turns the water yellow.

Calcium phosphate tends to clump up, causing the reaction rate between it and Lead to go down as the surface area decreases. So, the team incorporated hexagonal bevels inside the filter. That's an innovation, that will make the water spiral as it goes through and keep the powder from clumping.

Next, they will add a tiny spectrophotometer with a single-wavelength LED to the bottom of the filter cartridge, where the water gets dispensed. Their plan is to have an indicator light that turns on as soon as the detector identifies the yellow colour of Lead iodide. this will indicate that lead is in the water, even before the colour is detectable by eyes.

The team's goal is to make and sell their filters for less than $1 each.