Enabling in situ electro-regeneration systems for PFOA-laden spent activated carbon adsorbents reuse

Abstract

Adsorption is the main commercially used water treatment technology to remove per-and polyfluoroalkyl substances (PFAS) from water. Despite the high performance of this physical separation treatment, the endpoint of this technology is the production of PFAS-laden spent activated carbon. So far, several regeneration techniques have been used for spent activated carbon. However, activated carbon regeneration techniques remain challenging due to a limited understanding of cost/benefit analysis. In the present study, we developed the first proof of concept in situ electro-regeneration technique for the regeneration of perfluorooctanoic acid (PFOA, as a model long chain PFAS compound) laden-F400 using electro-assisted up-flow rapid small-scale column test (RSSCT) setup. The laboratory column experiments were conducted exploring sequential adsorption and electro-regeneration cycles. The results showed that the electro-regeneration of saturated F400 reinstated up to ∼60% of initial capacity. After the 1st regeneration cycle, the regeneration efficiency of spent F400 remained similar following 4 consecutive adsorption/regeneration cycles. The calculated operational cost for electro-regeneration was 0.70 kWh/kg, which is more competitive than current regeneration techniques. 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.