“There is a pressing need for mercury-removal technology that offers high selectivity, adsorption capacity, improved kinetics and a stable waste form,” Shas Mattigod of Pacific Northwest National Laboratory told nanotechweb.org.
As the basis of the material, Mattigod and colleagues used a mesoporous silica substrate with an average pore size of 6.5 nm and a surface area of around 900 m2/g. They functionalized the ceramic by adding a monolayer of alkylthiols to its pores. The alkylthiols attract and adsorb mercury ions.
Testing the material on a solution containing 4.64 mg/l of mercury indicated that the functionalized ceramic adsorbed about 99% of the mercury within five minutes. Once adsorbed, the mercury was highly resistant to leaching.
According to Mattigod, traditional methods for removing mercury are not as effective and also result in large quantities of residuals. “The mercury-loaded wastes and sludges may release mercury upon disposal, therefore special care needs to be exercised such as sequestering the waste and/or stabilizing it through additional treatment,” he said. “The large volume and high disposal costs of these residuals are the principal hurdles for using these methods.”
As well as cleaning up wastewater from coal-fired power stations, the thiol-SAMMS material could also remove mercury from water streams resulting from the vitrification of radioactive wastes, battery manufacturing, fluorescent lamp recycling and dental preparations. The technology could also be adapted to target substances such as lead, chromium or radionuclides instead of mercury.
“We are currently designing engineered forms of SAMMS such as membranes and/or fibre forms that can be deployed in the field,” added Mattigod.
The scientists reported their work at the American Chemical Society meeting in the US last week.