Decoloration and degradation of direct black 22 dye in aerated aqueous solution using gamma irradiation

The effect of radiation degradation of Direct Black 22 dye in aerated aqueous solution has been studied. Irradiation on direct dye was carried out at total absorbed doses 4 - 20 kGy (dose rate 5 kGy/hour), the initial pH were 3 - 11, and dye concentration were 0.05 - 0.20 g/L. The concentration of remained dye solution were measured using spectrophotometric method. The optimum condition of degradation was obtained at 20 kGy in aerated solution and initial pH7. At this condition, dye concentration of 0.05 g/L has been degraded 99% and pH of solution decreased up to 5. The decrease upon irradiation indicated the formation of low molecular weight compounds, such as organic acids. The degradation of the dye indicated the first-order reaction with the reaction speed constant (k) was 6,66 x 10-3/minute and the coefficient efficiency of radiolysis (k*) was 1.09 x 10-5 g/L/Gy. (author)