Oxidized Carbon Found Cost-Effective At Purifying Waters Contaminated With Radioactive Metals
In a new breakthrough, scientists at Rice University and Russia's Kazan Federal University have developed an oxidatively modified carbon (OMC) material that can remove radioactive waste from water in a cost-effective way.
The OMC was made by combining a coke-derived Powder C-seal F, used in the oil industry and a carbon-rich mineral called shungite. They leveraged the porosity of their carbon sources and expanded the surface area of the material through an oxidation process.
When treated with oxidizing chemicals, the carbon particles generate the oxygen molecules needed to absorb the toxic radioactive metals.
The oxidative modification expands the surface area of carbon with a "decoration" of oxygen molecules at the surface area of the material.
Fukushima Water Purification
Given the cost efficiency of the new material, researchers are raising hopes that its application can cure the contaminated water stored at Fukushima nuclear plant in Japan, which faced damage after a devastating earthquake and tsunami in 2011.
According to Tour, use of carbon in the material is significant as it offers many advantages unlike other materials used in removing radioactive waste from water. Such materials have to be stored along with the waste they capture and there is no option to burn them in incinerators as can be done with OMC.
Merely sending out infected water through OMC filters can pull out the radioactive elements and ensure safer discharge into the ocean.
"This could be a major advance for the cleanup effort at Fukushima," Tour said.
The premise of the new material is to provide advantages that enable separation of radioactive waste including uranium, thorium, and radium from water systems on an oxygen-rich surface that has particulate granular texture.
The OMC extricates radioactive elements such as uranium, thorium, and radium. One of the attractions of OMC is its low cost and supreme ability in absorbing radioactive toxic elements like cesium, strontium which were pushed into the environment during the meltdown of Fukushima plant.
The OMC particles from the two flavors derived from coke and shungite, appear like crumpled papers or roses with irregular petals.
The material's testing was done under two processes: first by mixing sorbents with contaminated water and second with column filtration in which the fluid is pulled by gravity to filter out contaminants.
For Tour and researchers, the OMC was an expanded opportunity to go beyond a sorbent they had discovered in graphene oxide.
The graphene oxide was good at removing strontium, yet the OMC is deemed better in extracting cesium, the hardest element requiring removal from Fukushima water.
Perhaps, the best part is that OMC is easier to synthesize and less expensive in a standard filtration system.
The mixing test conducted by researchers for OMCs yielded positive results. After mixing nonradioactive isotopes of strontium and cesium in spring water with OMC, they stirred it for two hours. The analysis of filtered out sorbent showed a clear measure of the particles left in the water.
The OMC from coke proved best in removing both strontium and cesium with purity of water increasing when volumes of sorbent were hiked.
With 800 milligrams of OMC1, 83 percent of cesium and 68 percent of strontium were removed from 100 milliliters of water.
The OMC2 made from shungite, same concentrations adsorbed 70 percent of cesium and 47 percent of strontium.
In column filtration tests, the OMCs gave a stellar performance. When 1,400 milliliters of contaminated water was flown through an OMC filter in 100-milliliter amounts, 93 percent of cesium and 92 percent of strontium was found removed in a single pass and helped researchers to isolate contaminants trapped in the filter material.