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Solvent-based regeneration of granular activated carbon

| By Scott Jenkins

Granular activated carbon (GAC) can be used to remove polyfluoroalkyl substances (PFAS) from groundwater and drinking water, but current methods to regenerate spent GAC are costly and require high temperatures of greater than 1,000°C. A team of scientists at Battelle Memorial Institute (Columbus, Ohio; www.battelle.org) has developed a solvent-based method for restoring PFAS-laden GAC that requires much less energy and time than the conventional method.

The Battelle researchers identified two organic-alcohol solvents that were effective for the GAC regeneration process and developed a product, known as GAC Renew, based on those solvents. To regenerate the GAC at a water-treatment facility, one treatment tank is taken offline while a second tank allows GAC treatment to continue. The regenerant solution is stored on site and is cycled through the tank for the number of bed volumes that best regenerate the GAC, according to Battelle. The number of bed volumes is determined during laboratory column studies. After the solution has regenerated the spent GAC, potable water is passed through that tank to rinse the GAC before putting it back online, Battelle explains.

The GAC Renew process can reactivate GAC at lower cost than heating the GAC, and the PFAS-removal performance of the solvent-regenerated GAC is better than virgin GAC, even after four solvent-regeneration cycles, Battelle says.

The spent regeneration solution can be distilled for recycling and the concentrated distillate treated on site with Battelle’s PFAS Annihilator Destruction Technology (see Chem. Eng., March 2022, p. 8).