Effect of the interaction between dye and acetic acid on the decomposition of Basic Green 4 with additive by ozone

This research investigated the ozonation of Basic Green 4 (BG4) under the presence of acetic acid (AA). This acid is used as a textile additive for many industrial dyes derived from triphenylmethane. Determining the effect of this additive on discoloration, degradation dynamics, and final by-product distribution is the main objective of this study. The reaction system was the ozonation of a dye solution in co-solvents. This solution (dye and AA) was considered a simplified version of real BG4 dyeing wastewaters supplied with additives. The dye concentration was set to 50, 150, and 250 mg/L without pH adjustment (pH = 3). This low value was forced by the AA. Ozonation reaction with dye was mainly done by a direct molecular mechanism. The discoloration dynamics of BG4 without and with the additive were determined by ultraviolet and visible wavelength spectroscopy. The dye decomposition and the intermediate and final product formation-decomposition dynamics were followed by high-performance liquid chromatography. The effects of AA in the ozonation results were significant in the following ways: 1) a possible complex, formed between AA and the dye, changed ozone consumption; 2) the presence of additive decelerated the dye discoloration and decomposition; and 3) the number of by-products was dissimilar in both systems, with and without the additive the ozonation. The accumulation of organic acids with low molecular weight was determined in both systems, with and without the additive. Only one by-product was obtained in ozonation when AA participated in the reactor. A possible reaction mechanism is proposed for the system dye-AA-ozone.