Adsorption onto granular activated carbon (GAC) is one of the most commonly used non-destructive techniques for the removal of long-chain per-and polyfluoroalkyl substances (PFAS) from water. However, the endpoint of this technology is the production of PFAS-laden spent carbon. Therefore, to prevent inadequate disposal of spent carbon, the development of environmentally friendly and cost-effective regeneration techniques for PFAS-laden GAC is urgently needed. In the present study, we developed the first in situ electro-regeneration technique for the regeneration of perfluorooctanoic acid (PFOA, as a model long chain PFAS compound) laden-F400 carbon using electro-assisted up-flow rapid small-scale column test (RSSCT) setup. The laboratory column experiments were conducted sequentially, with adsorption followed by electro-regeneration, using Titanium wire and spent F400 as the anode and cathode, respectively. The 250 mM sodium sulfate (Na2SO4) was used as the supporting electrolyte. The regeneration experiments were employed at 50% and 100% PFOA saturation levels after around 7,000 and 18,000 bed volumes, respectively. The results showed that the electro-regeneration of saturated F400 carbon reinstated up to ~60% of initial capacity. After the first regeneration cycle, the regeneration efficiency of spent F400 carbon following 4 consecutive adsorption/regeneration cycles remained similar. Moreover, the calculated operational cost of an electro-regeneration of spent F400 was 0.70 kWh/kg, which is more outcompete than current regeneration techniques such microwave regeneration (900 kWh/kg). Overall, this novel proof-of-concept approach can be used as a promising alternative regeneration technique to existing ones to minimize waste PFAS-laden adsorbents in landfills and decrease the amount of CO2 emissions associated with the incineration of these sorbents.

In situ electro-regeneration of per-and polyfluoroalkyl substances (PFAS)-spent carbon

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