Removing heavy metals from water with MOFs

0
217
A metal organic framework can remove lead from water samples, getting them to EPA-approved levels in seconds. Illustration/ American Chemical Society

RESEARCHERS reported in ACS Central Science a new material that can remove heavy metals and provide clean drinking water in seconds.

Wendy L. Queen and colleagues sought to attack this issue with materials called metal
organic frameworks (MOFs) that are networks of organic chemical ‘struts’ with metal nodes known to pull things like water and gases from air.

That ability, plus the large surface area and chemical tunability of MOFs make them a promising material to remove heavy metals selectively from water.

There are many sources of exposure to toxic heavy metals. Lead, in particular, has been used in paints, ceramic glazes, jewelry, toys and in pipes.

An estimated 1 billion people do not have access to clean drinking water, a problem expected to worsen with climate change, according to the World Health Organisation.

In addition, higher energy needs and increased use of heavy metals in industrial processes
have increased human exposure to these toxic materials from drinking water in recent decades.

Current commercial methods to remove heavy metals including lead from municipal drinking water can be expensive in terms of money and energy and are inefficient.

In addition, some current approaches either are single-use, are difficult to regenerate or can produce significant toxic waste as a side product.

The researchers created a water-stable MOF/polymer composite with cheap, environmentally and biologically friendly materials and tested its ability to remove heavy metals from water.

It had one of the highest reported removal capacities to date, removing over 1.6 times
its own weight of mercury and 40 percent of its weight in lead.

The researchers tested the MOFs in solutions with lead levels similar to those found in
contaminated water samples from Flint, Michigan. They found that the material can rapidly
reduce lead concentrations to 2 parts per billion, which is the US Environmental Protection Agency limit for drinkable levels.

Further, the researchers removed lead from various realworld water samples from the
Rhone River, the Mediterranean Sea and a wastewater treatment plant in Switzerland.

The researchers also demonstrated how the material could be regenerated easily without
toxic products. The authors say they are now pursuing using other specially designed MOFs
to remove other trace contaminants in water.

It had one of the highest reported removal capacities to date, removing over 1.6 times its
own weight of mercury and 40 percent of its weight in lead.