Electrochemical Transformation of Trace Organic Contaminants in the Presence of Halide and Carbonate Ions

Abstract

Electrochemical treatment on anodes shows promise for the oxidation of organic contaminants in industrial wastewater and reverse osmosis concentrate from municipal wastewater recycling due to the high conductivity of the matrix and the concomitant low energy demand. The effect of background electrolyte composition (Cl–, HCO3–, and NH4+) on the formation and fate of electrochemically produced heterogeneous (HO•ads and Cl•ads) and homogeneous (HOCl and HOBr) oxidants was evaluated on Ti–IrO2 and boron-doped diamond (BDD) electrodes using a suite of trace organic contaminants that exhibited varying reactivity with HO•, CO3•–, HOCl, and HOBr. The contributions of adsorbed and bulk oxidants to contaminant degradation were investigated. Results show that transformation rates for most contaminants increased in the presence of chloride and trace amounts of bromide; however, elevated concentrations of HCO3– often altered transformation rates due to formation of selective oxidants, with decreases in reactivity observed for electron-poor contaminants and increases in reactivity observed for compounds with amine and phenolic moieties. Using this information, rates of reactions on anode surfaces and measured production and loss rates for reactive homogeneous species were used to predict contaminant removal in municipal wastewater effluent. Despite some uncertainty in the reaction mechanisms, the model accurately predicted rates of removal of electron-rich contaminants but underestimated the transformation rates of compounds that exhibited low reactivity with HOCl and HOBr, possibly due to the formation of halogen radicals. The approach employed in this study provides a means of identifying key reactions for different classes of contaminants and for predicting the conditions under which anodic treatment of wastewater will be practical.

Sonoelectrochemical Degradation of Propyl Paraben: An Examination of the Synergy in Different Water Matrices

“…Despite that, in general, carbonate radicals are considered to have less oxidizing power than hydroxyl radicals; they are active for longer. Hence, if the target pollutant is an electron-rich organic compound with a kinetic constant (k) for the reaction with carbonate radical greater than 10 8 M −1 s −1 like, for example, sulfonamides, it is expected that the presence of carbonates will improve the removal rate [37]. pollutant for the reaction with the radicals, the adsorption at the electrode surface, and the accumulation at the bubble interface or the diffusion inside the cavity.…”

Recovery of Alum Sludge by using Membrane-Based Electrochemical Process

“…Ion exchange membranes constitute one of the alternative methods to separate the DOC for alum recovery (Prakash et al, 2004). The other organic removal is by conducting electrochemical oxidation process (Barazesh et al, 2016). Therefore, this CEM configuration seems to be more beneficial for the alum recovery than the AEM reactor configuration.…”

Combining Chemical and Biological Oxidation for Sustainable Treatment of Chloronitrobenzene in Anoxic Groundwater

“…For the purpose of this study, 2‐chloronitrobenzene ( o‐ CNB) was chosen as a model compound and (pre‐)oxidized by electrochemical oxidation. Electrochemical water treatment is an AOP that does not require chemical addition and offers flexibility in its implementation, either as ex situ treatment or as in situ reactive barrier for groundwater remediation (Martinez‐Huitle and Ferro 2006; Panizza and Cerisola 2009; Garcia‐Segura and Brillas 2011; Sirés and Brillas 2012; Chen et al 2014; Barazesh et al 2016). Dimensionally stable titanium mixed‐metal oxide (Ti‐MMO) electrodes were selected based on their proven effectiveness in persistent organic contaminant mineralization, long service life, wide availability, and relatively low cost (Martinez‐Huitle and Ferro 2006; Wu et al 2014; Jasmann et al 2016; Blotevogel et al 2019).…”