Per- and polyfluoroalkyl substances remediation

Abstract

The present invention relates to reduction of per- and polyfluoroalkyl compounds (PFAS) in a desired zone of treatment for the continuous remediation of contaminated solids and liquids. In particular, embodiments of the present invention relate to the in-situ treatment of solids and liquids by a particular combination of reagent and conditions. The reagents include an oxidant and a metal catalyst. Disclosed method combines low temperature thermal remediation with chemical oxidation to destroy poly- and perfluoroalkyl substances in-situ. The disclosed methods may enhance destruction of organic contaminants in the desired zone of treatment. The present invention also relates to a method for applying the remediation compositions to contaminated sites and controlling the process by monitoring the degradation event to achieve maximum reduction of PFAS.

We claim: 
     
         1 . A method for in-situ remediation of per- and polyfluoroalkyl compounds (PFAS) in a desired zone of treatment, the method comprising:
 measuring a groundwater fluoride concentration within the desired zone of treatment;   verifying an ambient in-situ thermal environment within the desired zone of treatment having a temperature >20 degrees centigrade;   dispersing a transition metal catalyst into the ambient in-situ thermal environment creating an ambient in-situ thermal catalyst rich environment;   introducing, to the ambient in-situ thermal catalyst rich environment, an oxidant wherein the catalyst and the oxidant within the ambient in-situ thermal catalyst rich environment interact generating high redox potential free-radicals oxidizing PFAS compounds producing, inter alia, fluoride;   calculating a target groundwater fluoride concentration generated through PFAS destruction within the desired zone of treatment, and naturally occurring groundwater fluoride concentration;   monitoring the groundwater fluoride concentrations and a rate of change of fluoride concentration within the desired zone of treatment; and   responsive to the monitored groundwater fluoride concentrations being less than the target groundwater fluoride concentration in the desired zone of treatment, injecting into the desired zone of treatment additional oxidant.   
     
     
         2 . The method of  claim 1  wherein the high redox potential free-radicals oxidize perfluorooctanoic acid (PFOA) in the desired zone of treatment. 
     
     
         3 . The method of  claim 1 , wherein the oxidant is a peroxy-based/sulfur-based material. 
     
     
         4 . The method of  claim 3 , wherein the oxidant is persulfate. 
     
     
         5 . The method of  claim 3 , wherein the oxidant is hydrogen peroxide. 
     
     
         6 . The method of  claim 1 , wherein the metal catalyst is uniformly dispersed throughout the desired zone of treatment. 
     
     
         7 . The method of  claim 1 , wherein the metal catalyst is regenerated for each cycle of oxidation. 
     
     
         8 . The method of  claim 1 , wherein the metal catalyst is regenerated upon interacting with the oxidant. 
     
     
         9 . The method of  claim 1 , wherein responsive to the rate of change fluoride concentrations being less than zero, further dispersing additional catalyst. 
     
     
         10 . The method of  claim 1 , wherein the metal catalyst is regenerated by decarboxylation of a carboxylic group. 
     
     
         11 . The method of  claim 1 , wherein the metal catalyst is replenished after monitoring the rate of release of fluoride in groundwater. 
     
     
         12 . The method of  claim 1 , wherein the PFAS compounds are destroyed while they are flushed through the vadose zone, thereby preventing groundwater contamination. 
     
     
         13 . The method of  claim 1 , wherein the desired zone of treatment includes a material selected from the group consisting of a biomass, an organic compound, an inorganic compound in the form of a solid, and an inorganic compound in the form of an aqueous solution. 
     
     
         14 . The method of  claim 1 , wherein the molar ratio of catalyst to oxidant is of the order of 1:10100-1:1000. 
     
     
         15 . The method of  claim 1 , wherein the ambient in-situ thermal environment is ≥20 degrees centigrade and ≤35 degrees centigrade. 
     
     
         16 . The method of  claim 1 , wherein the ambient in-situ thermal environment is ≥20 degrees centigrade and ≤30 degrees centigrade. 
     
     
         17 . The method of  claim 1 , wherein the ambient in-situ thermal environment is ≥20 degrees centigrade and ≤40 degrees centigrade 
     
     
         18 . The method of  claim 1 , wherein the oxidant is consumed after producing free radicals. 
     
     
         19 . The method of  claim 1 , wherein 80% or more of oxidation of PFAS is achieved within 72 hrs. 
     
     
         20 . The method of  claim 19 , wherein the PFAS compound comprise one or more per- and polyfluorocarboxylic acids or conjugate bases thereof. 
     
     
         21 . The method of  claim 1 , further comprising establishing the ambient in-situ thermal environment through passive solar heating of the desired zone of treatment. 
     
     
         22 . The method of  claim 1 , further comprising establishing the ambient in-situ thermal environment through active heating generated by mechanical, electrical or chemical sources of the desired zone of treatment. 
     
     
         23 . A system for in-situ reduction of per- and polyfluoroalkyl compounds (PFAS) in a desired zone of treatment, the method comprising:
 a potentiometric sensor configured to measure in-situ a groundwater fluoride concentration within the desired zone of treatment;   one or more thermal devices configured to verify an ambient in-situ thermal environment within the desired zone of treatment having a temperature >20 degrees centigrade;   a dispersing device configured to disperse a transition metal catalyst into the ambient in-situ thermal environment creating an ambient in-situ thermal catalyst rich environment;   an oxidant pump configured to introduce, to the ambient in-situ thermal catalyst rich environment, an oxidant wherein the catalyst and the oxidant within the ambient in-situ thermal catalyst rich environment interact generating high redox potential free-radicals oxidizing PFAS compounds producing, inter alia, fluoride;   a processor communicatively coupled to a non-transitory readable storage medium tangibly embodying a program of instructions executable by the processor, for
 calculating a target groundwater fluoride concentration generated through PFAS destruction and a rate of change of rising fluoride concentration within the desired zone of treatment, and naturally occurring groundwater fluoride concentration; 
 monitoring the groundwater fluoride concentrations and a rate of change of fluoride concentrations within the desired zone of treatment; and 
 responsive to the monitored groundwater fluoride concentrations being less than the target groundwater fluoride concentration in the desired zone of treatment, injecting, by the oxidant pump into the desired zone of treatment, additional oxidant. 
   
     
     
         24 . The system of  claim 23 , wherein the oxidant is a peroxy-based/sulfur-based material. 
     
     
         25 . The system of  claim 24 , wherein the oxidant is persulfate. 
     
     
         26 . The system of  claim 24 , wherein the oxidant is hydrogen peroxide. 
     
     
         27 . The system of  claim 24 , wherein the oxidant is a combination of oxidants selected from a class consisting of persulfate and hydrogen peroxide. 
     
     
         28 . The system of  claim 23 , wherein the dispersing device is configured to distribute the metal catalyst equally throughout the desired zone of treatment. 
     
     
         29 . The system of  claim 23 , further comprising instructions executable by the processor for dispersing additional catalyst to the desired zone of treatment responsive to the rate of rising fluoride concentrations being less than zero. 
     
     
         30 . The system of  claim 23 , wherein the desired zone of treatment includes a material selected from the group consisting of a biomass, an organic compound, an inorganic compound in the form of a solid, and an inorganic compound in the form of an aqueous solution.