Electrochemical and sonoelectrochemical processes applied to amaranth dye degradation

Amaranth dye is an organic compound largely used in the food and beverage industries with potential toxicity effects on humans. It can be found as a pollutant species in aquatic environments and has been classified as an endocrine disruptor. This study describes amaranth degradation upon ultrasonication associated with an electrochemical system that uses a boron-doped diamond anode BDD, defined as a sonoelectrochemical process. Ninety-minute electrolyses were performed using current densities in the 10-50 mA cm−2 range, and the concentration decay, pH, energy and current efficiencies, as well as the discoloration rate were evaluated. The amaranth concentration decayed as a function of electrolysis time and the reactions obeyed pseudo first-order kinetics, with an apparent constant rate between 10−1 and 10−3 min−1. The electrochemical and sonoelectrochemical processes at 35 mA cm−2 yielded TOC removal values between 92.1% and 95.1% respectively, after 90 min. Current efficiency values obtained for both processes were 18.2% and 23.6%. Exhaustive 5 h electrolysis was performed and the degradation products were identified by HPLC-MS. A mechanism for the degradation of amaranth was proposed based on an analysis of the aromatic and aliphatic intermediates.