Electrochemical technologies for per‐ and polyfluoroalkyl substances mitigation in drinking water and water treatment residuals

Abstract

Water treatment technologies are needed that can convert per-and polyfluoroalkyl substances (PFAS) into inorganic products (e.g., CO 2 , F À ) that are less toxic than parent PFAS compounds. Research on electrochemical treatment processes such as electrocoagulation and electrooxidation has demonstrated proof-of-concept PFAS removal and destruction. However, research has primarily been conducted in laboratory matrices that are electrochemically favorable (e.g., high initial PFAS concentration [μg/L-mg/L], high conductivity, and absence of oxidant scavengers). Electrochemical treatment is also a promising technology for treating PFAS in water treatment residuals from nondestructive technologies (e.g., ion exchange, nanofiltration, and reverse osmosis). Future electrochemical PFAS treatment research should focus on environmentally relevant PFAS concentrations (i.e., ng/L), matrix conductivity, natural organic matter impacts, short-chain PFAS removal, transformation products analysis, and systems-level analysis for cost evaluation.

Examining Current and Future Applications of Electrocoagulation in Wastewater Treatment

“…EC has the ability to eliminate PFAS through either non-destructive phase separation or destructive oxidative pathways. Compared to other PFAS treatment methods that are destructive, such as sonolysis, ultraviolet (UV) advanced oxidation, advanced reduction, and photocatalysis, EC requires less energy input [105]. Most studies using EC to remove PFAS have concentrated on non-destructive methods that involve the sorption of PFAS to metal hydroxide flocs created using sacrificial electrodes [105].…”

“…Compared to other PFAS treatment methods that are destructive, such as sonolysis, ultraviolet (UV) advanced oxidation, advanced reduction, and photocatalysis, EC requires less energy input [105]. Most studies using EC to remove PFAS have concentrated on non-destructive methods that involve the sorption of PFAS to metal hydroxide flocs created using sacrificial electrodes [105]. Iron and aluminum are the commonly used electrodes, while zinc has shown greater PFOA removal compared to iron and aluminum [106].…”

“…PFAS sorption to hydroxides was primarily attributed to hydrophobic interactions between PFAS species and the metal hydroxide surface via multilayer sorption [106]. Moreover, studies suggest that EC can produce oxidation reactions through anode-surface oxidation, reactive iron intermediates, or Fenton processes (presuming there is H 2 O 2 in the matrix) at low pH, which may lead to PFAS degradation [105]. Recent research has demonstrated the oxidative ability of iron-electrocoagulation for PFAS removal, which involves direct electron transfer and oxidant generation, leading to the production of shorter-chain PFAS compounds [107].…”

PFAS are forever? The state of the science and research needs for analyzing and treating PFAS‐laden water

“…The issues with membrane retentate streams also apply to other hard‐to‐treat waters such as landfill leachates, remediation waters, and wastewaters. To identify approaches for treating residuals from non‐destructive water treatment processes, Ryan et al (2021) review electrochemical technologies such as electrocoagulation and electrooxidation. It is found that electrochemical treatment is also promising for residual streams of IX, NF, and RO processes.…”