Electrogeneration of disinfection byproducts at a boron-doped diamond anode with resorcinol as a model substance

Electrochemical disinfection in chloride electrolyte with a boron-doped diamond (BDD) electrode has unique advantages due to the high oxidizing ability of active chlorine and reactive oxygen species produced under certain conditions in the electrolysis. However, the electrogeneration of disinfection byproducts (DBPs) in the presence of organics in the system has rarely been reported. In this study, the discontinuous formation of DBPs (chloroform, chlorate and perchlorate) was investigated in model water containing chloride electrolyte (10 mM) with a BDD anode in the presence of resorcinol (0.5 mM) at a current density of 20 mA cm−2. We found that the formation of chloroform and chlorate increased with the free available chlorine production at the beginning and reached peaks at 2 h (0.01 mM), 4 h (1.67 mM), respectively. When the free available chlorine started to decrease, chloroform was gradually mineralized and chlorate was oxidized to perchlorate due to the strong and non-selective oxidizing ability of the BDD. After electrolysis for 25 h, only perchlorate was left (3.84 mM). So inorganic DBPs should be carefully watched in the BDD system. The chloride concentration in the electrolyte affected the production of all three DBPs, due to its influence on the active chlorine production. Organic was not involved in the chlorate and perchlorate formation, and thus the resorcinol concentration had little impact on inorganic DBPs. DBPs formation at acidic pH was lower than that in the basic condition, mainly due to the different forms of resorcinol and chlorine existing at different pH values. Compared with other endocrine disruptors (dimethyl phthalate, diethyl phthalate and bisphenol-A), resorcinol with high active structure showed the greatest reactivity in DBPs production.

► DBPs formation was studied in BDD cell with several organics.
► Accumulated chloroform was wholly mineralized in the electrolysis.
► Chlorate produced was oxidized to perchlorate as electrolysis continued.
► Inorganic byproducts should be carefully watched in electrolysis with BDD.
► Resorcinol had the greatest reactivity for DBPs production in the studied precursors.