Electrochemical dechlorination of trichloroethylene in the presence of natural organic matter, metal ions and nitrates in a simulated karst media

Abstract

A small-scale flow-through limestone column was used to evaluate the effect of common coexisting organic and inorganic compounds on the electrochemical dechlorination of trichloroethylene (TCE) in karst media. Iron anode was used to produce ferrous ions and promote reducing conditions in the column. The reduction of TCE under 90 mA current, 1 mL min−1 flow rate, and 1 mg L−1 initial TCE concentration, was inhibited in the presence of humic acids due to competition for direct electron transfer and/or reaction with atomic hydrogen produced at the cathode surface by water electrolysis. Similarly, presence of 10 mg L−1 chromate decreased TCE reduction rate to 53%. The hexavalent chromium was completely reduced to trivalent chromium due to the ferrous species produced from iron anode. Presence of 5 mg L−1 selenate decreased the removal of TCE by 10%. Chromium and selenate complexation with dissolved iron results in formation of aggregates, which cover the electrodes surface and reduce TCE dechlorination rate. Presence of 40 mg L−1 nitrates caused reductive transformation of TCE up to 80%. Therefore, TCE removal is influenced by the presence of other contaminants that are present as a mixture in groundwater in the following order: humic acid, chromate, selenate, and nitrate.

Assessment of groundwater quality and remediation in karst aquifers: A review

“…One of the promising, cost-effective methods for minimizing the exposure pathways is electrochemical treatment: environmentally friendly (option of using solar power), independent (no other remedial actions needed) and controllable with regard to the rates of redox reactions. The high removal percentage for various contaminants in karst groundwater has been achieved in laboratory and pilot scale studies (Fallahpour, 2016; Gregor et al, 2017; Mao et al, 2012).…”

Electrocatalytic Reduction of Nitrate Using Magnéli Phase TiO2 Reactive Electrochemical Membranes Doped with Pd-Based Catalysts

“…The O 2 reduction reaction (ORR) occurs at similar cathodic potentials as NO 3 − reduction, 40 and dissolved organic matter can adsorb and block catalytic sites. 41,42 Therefore, the effects of dissolved oxygen, bicarbonate, and a surface water sample (Table 1) on NO 3 − reduction were investigated.…”

Transformation of tetrachloroethylene in a flow-through electrochemical reactor

“…Such knowledge is required for development of a more robust test design for enhanced applicability and feasibility testing at conditions simulating that of potential in-situ applications. Previous work has studied electrochemical removal of mainly TCE in static reactors [37,56], stirred reactors [22,57], recirculated reactors [23,35,40], vertical flow-through reactors [24,34,[41][42][43][44]56,58], applied constant voltage [39,59,60] or studied electrochemistry in combination with other remediation strategies, e.g. bioremediation [29,[61][62][63][64].…”

“…Hence, resistivity was 5 times higher in the porous matrix. An increase in potential difference as the alkaline front progresses towards the anode in a porous matrix has been observed[72].Vertical oriented reactors are applied in most studies on flow-through electrochemical removal of chlorinated ethenes[24,32,58,33,34,[40][41][42][43][44]55]. One major advantage is automatic venting of gases generated, since gases released from the electrodes will bubble up through the reactor and leave the reactor with the effluent.…”