Galvanic Removal of Polyfluorinated Compounds from Water

A low cost, low energy breakthrough for the removal and destruction of Polyfluorinated

“Forever Chemicals”

Donald Luke, Carlos Borras

Nuquatic

Our process, based on a Galvanic Cell, originally designed to remove nutrients, primarily phosphorus from various water sources, combines a continuous flow reactor with a aluminum/copper (Al-Cu) galvanic reaction; our reaction occurs based on electrochemical principles and thus requires no additional energy. Aside from phosphorus removal, we’ve determined that PFOA and PFOS can be concentrated using our continuous galvanic reactor. Per and polyfluoroalkyl substances, or PFAs for short, are a rapidly growing concern due to recent studies connecting PFA exposure to cancer and immune system problems. With over 9000 PFA variants identified to date, research into the removal and destruction of these molecules is vital to the health and safety of the world population. Two common PFA molecules are perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA); the EPA has published health advisory limits (interim) of 0.02 ppt and 0.004 ppt, respectively, for these molecules in drinking water. Once concentrated, we can destroy these molecules using a variety of methods in a cost-effective manner due to the high concentration ratio of the PFOS/PFOA compounds. Our process provides a simple, inexpensive and low energy solution to PFA contamination in all water sources.

Part II

Complex organic compounds that persist in water even after traditional treatment methods and that in low concentrations have harmful effects on human health are a challenging riddle to solve. These compounds have a very high chemical stability and are known generically as "recalcitrant compounds" because traditional removal capabilities are very low, or very expensive. The most convenient way to eliminate them is through mineralization in an Advanced Oxidation Processes (AOP) that focuses on generation of several radical species with high oxidizing potential. The radicals facilitate decomposition, breaking of chemical bonds and the transfer of oxygen to the organic compounds. Among the most known AOPs are combinations of ozone, hydrogen peroxide, ultraviolet radiation, photocatalysis, and electrochemistry, however the implementation of these processes is generally limited by the high associated costs.

Our patented galvanic cell changes this paradigm.  The cathodic protection by the sacrificial anode of the cathode prevents its dissolution even in the presence of high concentrations of H2O2. The cathode develops a multiplicity of surface sites that allow the generation of OH radicals through a Fenton-like reaction even at relatively high pH values. Measurements of the generation rate of OH radicals from the electric current in the galvanic cell show a dependence on the concentration of active sites on the copper surface and on the conductivity of the treated water. Experiments were conducted in which the Total Organic Carbon (TOC) was measured when some of these "recalcitrant compounds" were exposed to our Galvanic cell. Our results indicate that their removal occurs through two mechanisms – First, chemical combustion by the generated radicals and second through the adsorption of intermediate organic compounds in the surface the  particles of hydroxide produced by the anodic reaction of the galvanic cell. The partition between these two processes depends on the Hammett substituent constant of the generated intermediates. The adsorption process in our device represents a significant increase in the removal efficiency of organic compounds, reducing the costs associated with the addition of H2O2.