New filters efficiently remove heavy metals from water

By , on July 27, 2017


The academic seal of Rice University. A shield divided by a chevron, carrying three owls as charges, with scrollwork saying LETTERS, SCIENCE, ART (Photo By Rice University Identity Standards, Fair Use)
The academic seal of Rice University. A shield divided by a chevron, carrying three owls as charges, with scrollwork saying LETTERS, SCIENCE, ART (Photo By Rice University Identity Standards, Fair Use)

HOUSTON, July 28 — Carbon nanotubes immobilized in a tuft of quartz fiber have the power to remove toxic heavy metals from water, according to researchers at the Rice University of Texas.

According to a news release published Thursday by the Rice University, the filters produced in the lab of Rice University chemist Andrew Barron by then-high school student and lead author Perry Alagappan absorb more than 99 percent of metals from samples laden with cadmium, cobalt, copper, mercury, nickel and lead.

The researchers calculated 1 gram of the material could treat 83,000 liters of contaminated water to meet World Health Organization standards — enough to supply the daily needs of 11,000 people.

Once saturated, the filters can be washed with a mild household chemical like vinegar and reused.

The robust filters consist of carbon nanotubes grown in place on quartz fibers that are then chemically epoxidized.

Lab tests showed that scaled-up versions of the “supported-epoxidized carbon nanotube” (SENT) filters proved able to treat 5 liters of water in less than 1 minute and be renewed in 90 seconds. The material retained nearly 100 percent of its capacity to filter water for up to 70 liters per 100 grams of SENT, after which the metals contained could be extracted for reuse or turned into a solid for safe disposal.

While the quartz substrate gives the filter form and the carbon nanotube sheath makes it tough, the epoxidation via an oxidizing acid appears to be most responsible for adsorbing the metal, they determined.

The lab’s analysis of the new filters appears this month in Nature’s open-access Scientific Reports.