A cationic inorganic layered material provides high-capacity removal of metallic anionic pollutants that now are difficult and expensive to eliminate from water, say its developers at the University of California Santa Cruz. The material, a copper hydroxide ethanedisulfonate dubbed SLUG-26 (Figure 1), boasts high adsorption capacity and thermal and chemical stability, is easily recovered by filtration, requires no pretreatment, and doesn't suffer interference from carbonate, the researchers note. It represents an entirely new transition-metal-based cationic metalate, they add.
"Our goal for the past 12 years has been to make materials that can trap pollutants, and we finally got what we wanted. The data show that the exchange process works," says Scott Oliver, an associate professor of chemistry.
The material can trap radioactive species, as well as industrial pollutants and pharmaceutical residues. The researchers initially are focusing on removing technetium from radioactive waste, and perchlorate and chloride from industrial wastewater. They have conducted some experiments with organic anions, salicylic acid and ibuprofen.
The team must address to two key issues: the cost of the material and its regeneration, says Oliver. "We are trying to move to cheaper metal as the building block… copper is cheaper than silver but still expensive… Ethylenedisulfonate is pricey as well but could be recovered after synthesis and exchange," he explains. "Our earlier material based on silver regenerated nicely… [but that's] not the case yet with the Cu-based SLUG-26." Initial efforts for regenerating perchlorate-loaded material will focus on heating and sonication, he expects.
A number of companies already have expressed interest in cooperating on development of the material, he notes. Producing it on an industrial scale shouldn't pose issues, he adds.
More details on the synthesis and performance of SLUG-26 appear in an article in Angewandte Chemie International.