Although GAC is less environmentally friendly compared to IX, several studies have identified GAC as a promising treatment technology, particularly for initial high contaminant loads, low dissolved organic carbon, concentrations, longer-chained PFAS including, PFOA and PFOS. Proper reactivation techniques can mitigate GAC's negative environmental impacts. For instance, thermally reactivated GAC has been found to have lower impacts than single-use GAC and even regenerable IX treatments. Utilizing off-site thermal reactivation and reuse of spent GAC media significantly reduces impacts by decreasing the need for new adsorbent material, and operating at lower temperatures (e.g., 815°C compared to 1200°C for hazardous waste incinerators). Regeneration techniques for IX resins play a key role in its environmental sustainability. Regenerable IX systems, while generally less impactful than single-use GAC, can have significant environmental impacts due to the infrastructure and chemical-intensive processes required for resin regeneration and regenerant recycling. The environmental impacts of IX resins regeneration could be reduced by recycling methanol and/or brine, thereby, decreasing the amount of waste sent to incineration. However, altering the composition of the regeneration solution requires careful consideration as replacing NaCl with alternative salts can increase environmental impacts. Another study showed that the regeneration and reuse of IX resins with electrochemical oxidation in groundwater significantly reduces global warming potential (GWP), especially when the energy efficiency of oxidation is between 192 kWh/m³ and 656 kWh/m³. Regeneration and reuse of IX resins coupling with electrochemical oxidation had the lowest GWP, reducing it by approximately 49% compared to IX following incineration. These findings suggest that regeneration and reuse of IX resins could be one of the most environmentally friendly options for treating PFAS-contaminated groundwater.