title: Electrode effects on temporal changes in electrolyte pH and redox potential for water treatment.
abstract: The performance of electrochemical remediation methods could be optimized by controlling the physicochemical conditions of the electrochemical redox system. The effects of anode type (reactive or inert), current density and electrolyte composition on the temporal changes in pH and redox potential of the electrolyte were evaluated in divided and mixed electrolytes. Two types of electrodes were used: iron as a reactive electrode and mixed metal oxide coated titanium (MMO) as an inert electrode. Electric currents of 15, 30, 45 and 60 mA (37.5 mA L(-1), 75 mA L(-1), 112.5 mA L(-1) and 150 mA L(-1)) were applied. Solutions of NaCl, Na(2)SO(4) and NaHCO(3) were selected to mimic different wastewater or groundwater compositions. Iron anodes resulted in highly reducing electrolyte conditions compared to inert anodes. Electrolyte pH was dependent on electrode type, electrolyte composition and current density. The pH of mixed-electrolyte was stable when MMO electrodes were used. When iron electrodes were used, the pH of electrolyte with relatively low current density (37.5 mA L(-1)) did not show significant changes but the pH increased sharply for relatively high current density (150 mA L(-1)). Sulfate solution showed more basic and relatively more reducing electrolyte conditions compared to bicarbonate and chloride solution. The study shows that a highly reducing environment could be achieved using iron anodes in divided or mixed electrolytes and the pH and redox potential could be optimized using appropriate current and polarity reversal.
authors.affiliation: Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Ciblak
authors.forename: Xuhui
authors.initials: X
authors.lastname: Mao
authors.forename: Ingrid
authors.initials: I
authors.lastname: Padilla
authors.forename: Dorothy
authors.initials: D
authors.lastname: Vesper
authors.forename: Iyad
authors.initials: I
authors.lastname: Alshawabkeh
authors.forename: Akram N
authors.initials: AN
authors.lastname: Alshawabkeh
mesh_terms: D004566:Electrodes; D004572:Electrolysis; D004573:Electrolytes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry*; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D004573:Electrolytes; D010087:Oxides; D017670:Sodium Compounds; D014025:Titanium; D007501:Iron