Simultaneous electro-oxidation of phenol, CN−, S2− and NH4+ in synthetic wastewater using boron doped diamond anode

Abstract

Electrochemical decontamination of phenolic synthetic wastewater containing CN−, S2− and NH4+ using a boron-doped diamond (BDD) electrode was investigated. The removal of phenol, its oxidation byproducts, total organic carbon (TOC), chemical oxygen demand (COD), and the inorganic species were evaluated in relation to specific energy consumption (SEC) and average current efficiencies (ACE) in single, binary, ternary and quaternary matrices of the inorganic species cohabiting phenol in solution. The total amount of COD removal, ACE and SEC were found to depend on the nature of ions in solution and were also proportional to the degree of inorganic species in the matrix. The decay kinetics of phenol as well as the inorganic species in different matrices mainly follow first order kinetics. ACE for binary and higher matrices values of 44.3–58.8% and 58.9–79.3%, respectively, indicate 132–207% and 208–315% increase in ACE, respectively, as compared to the 19.1% ACE when phenol was present alone. The SEC of 57.0 kWh/kg-COD estimated for the single phenol matrix dropped from 57kWh/kg-COD to between 15.1–20.6 and 7.83–15.2kWh/kg-COD for the multicomponent matrices which corresponds to a percent decrease of 63.2–73.5% and 73.3–86.3%, respectively. Presence of the inorganic species insignificantly affected phenol oxidation, though they delayed the attainment of steady state of complete decontamination depending on the species in the matrix. This study demonstrates the viability of oxidation at BDD anodes as an alternative treatment means for effective decontamination of phenolic wastewater containing inorganic species.