LAUSR

Abstract The potential of carbon doped zinc oxide nanoparticles (C-ZnO NPs) as a catalyst for microwave (MW) induced catalytic process (MW/C-ZnO NPs) was investigated for the degradation of brilliant green dye (BG). The synthesized C-ZnO NPs were characterized using XRD, FESEM, Raman, EDS, TGA and Zeta potential analysis. As a precursor, BG removal experiment was conducted at the initial BG dye concentration of 60 mg/L, C-ZnO NPs dose of 250 mg/L and MW irradiation of 10 min. In MW alone system, BG degradation of 47.7% was observed in 10 min whereas introduction of C-ZnO NPs in MW system has enhanced the efficiency to ∼90%. Subsequently, the effect of C-ZnO dose (0-500 mg/L), BG dye concentration (20-100 mg/L), and MW irradiation time (300-900 sec) on BG removal was evaluated using the central composite design (CCD) of experiments. Based on the experimental data, a quadratic model was developed and used for predicting BG removal. The analysis of variance (ANOVA) has confirmed that the model can predict accurately the BG removal within the experimental range (R2∼0.987). Using the CCD data, the cost-analysis was carried out and it has revealed that the optimum cost was 174 $/kg of BG removed at MW irradiation time of 7.0 min and BG concentration of 36.0 mg/L. Finally, LC-MS analysis was used to find BG degradation pathway and it showed that BG has degraded into simpler compounds. Moreover, micro-toxicity analysis demonstrated that MW/C-ZnO NPs treatment of BG has reduced the toxicity from 81% to 10% at 15 min exposure.