PFAS remediation using high redox potential free-radicals
Oxidation of per- and polyfluoroalkyl compounds (PFAS) contaminated solids and liquids in an in-situ desired zone of treatment using high redox potential free-radicals. An oxidant and a metal catalyst are combined forming a low temperature thermal remediation of PFAS through chemical oxidation in-situ.
1. A method for remediation of per- and polyfluoroalkyl substances (PFAS), the method comprising: forming an in-situ zone of treatment wherein forming includes measuring an initial groundwater fluoride concentration within the in-situ zone of treatment and verifying a thermal environment within the in-situ zone of treatment having a temperature >20 degrees centigrade;
dispersing an initial quantity of a transition metal catalyst into the thermal environment creating a catalyst rich thermal environment;
introducing to the catalyst rich thermal environment an initial quantity of an oxidant, wherein the initial quantity of the oxidant and the initial quantity of the transition metal catalyst within the catalyst rich thermal environment are at an initial molar ratio between 1:10-1:250, generating high redox potential free-radicals thereby oxidizing PFAS compounds by the high redox potential free-radicals producing, inter alia, fluoride;
calculating a rate of change of groundwater fluoride concentration within the in-situ zone of treatment;
monitoring the rate of change of groundwater fluoride concentration within the in-situ zone of treatment;
introducing an additional quantity of oxidant to the catalyst rich thermal environment if the rate of change of groundwater fluoride concentration in the catalyst rich thermal environment is not substantially zero until the rate of change of groundwater fluoride concentration in the catalyst rich thermal environment is substantially zero;
optionally adding an additional quantity of the transition metal catalyst in the catalyst rich thermal environment; and
responsive to the rate of change of groundwater fluoride concentration in the catalyst rich thermal environment being substantially zero upon introduction of the additional quantity of oxidant and replenishing of the transition metal catalyst, dispersing an additional quantity of the transition metal catalyst to the catalyst rich thermal environment until the rate of change of groundwater fluoride concentration in the catalyst rich thermal environment is substantially zero,
wherein the oxidant is a peroxy-based material or a sulfur-based material.
2. The method of claim 1 , wherein the oxidant is persulfate.
3. The method of claim 1 , wherein the transition metal catalyst is silver.
4. The method of claim 2 , wherein the oxidant is hydrogen peroxide.
5. The method of claim 1 , wherein the transition metal catalyst is uniformly dispersed throughout the in-situ zone of treatment.
6. The method of claim 1 , wherein the transition metal catalyst is regenerated for each cycle of oxidation.
7. The method of claim 1 , wherein the transition metal catalyst is regenerated upon interacting with the oxidant.
8. The method of claim 1 , wherein the transition metal catalyst is regenerated by decarboxylation of a carboxylic group.
9. The method of claim 1 , further comprising replenishing the transition metal catalyst responsive to monitoring a rate of release of fluoride in groundwater.
10. The method of claim 1 , further comprising destroying the PFAS as they are flushed through a vadose zone, thereby addressing current and preventing subsequent groundwater contamination.
11. The method of claim 1 , wherein the in-situ zone of treatment includes an inorganic compound in the form of an aqueous solution.
12. The method of claim 1 , wherein the molar ratio of the oxidant to catalyst is of the order of 1:10-1:150.
13. The method of claim 1 , wherein the thermal environment is ≥20 degrees centigrade and ≤35 degrees centigrade.
14. The method of claim 1 , wherein the thermal environment is ≥20 degrees centigrade and ≤30 degrees centigrade.
15. The method of claim 1 , wherein the thermal environment is ≥20 degrees centigrade and ≤40 degrees centigrade.
16. The method of claim 1 , wherein the oxidant is consumed after producing free radicals.
17. The method of claim 1 , wherein the PFAS compounds comprise one or more per- and polyfluoroalkyl acids or conjugate bases thereof.
18. The method of claim 1 , further comprising calculating a soil oxidant demand (SOD) value, and wherein the SOD value is used to estimate the initial quantity of the transition metal catalyst, the initial quantity of the oxidant, and the initial molar ratio.
19. The method of claim 1 , further comprising verifying a pH condition in the in-situ zone of treatment between neutral pH and acidic pH.
20. The method of claim 1 , wherein the transition metal catalyst is added to the in-situ zone of treatment by use of a catalyst dispersing device, and the oxidant is added to the zone of treatment by use of an oxidant pump.