SYNTHESIS OF ZINC NANOPARTICLES BY ELECTROCHEMICAL METHOD: CHARACTERIZATION AND APPLICATION

Abstract

In this study, zinc oxide nanoparticles were synthesized using electrochemical method. Zinc was used as electrode whereas oxalic acid in aqueous solution was used as an electrolyte. A L9 (34) Taguchi optimization methodology was used to find out the individual and interactive effect of all four independent experimental parameters namely pH (pH0): 5-8, oxalic acid concentration (m): 0.05-0.15 M, conductivity (k): 20-30 (mS/cm) and operating voltage (Vo): 5-8 V. These experimental parameters were optimized so as to maximize the productivity (g) and correspondingly find out specific energy consumption (kW h/kg) and specific electrode consumption (kg/kg). At the optimum condition of pH. = 5, m = 0.05 M, k 30 (mS/ cm) and V0 = 8 V, values of productivity, SENC and SELC were found to be 1.03 g, 3.79 kW hlkg and 1.76 kg/kg, respectively. Nanoparticles synthesized at optimum conditions have been further characterized by scanning electron microscopy, X-ray - diffraction and UV—Visible diffuse reflectance spectroscopy techniques so as to confirm its ZnO nature. The BET surface area at optimum condition was 39.53 m2/g. The purity of the synthesized ZnO was found to be 94.15 %. Taguchi optimization methodology was applied on four parameters namely catalyst dosage (g/1), 1-1202: C6H5NO2 ratio, pH, and time (h) duration of reaction were considered for optimizing degradation efficiency for nitrobenzene. Degradation efficiency was found to increases with increase in 1-1202 : C6H5NO2 ratio and decreases in catalyst dosage and pH. Optimum parameter condition for degradation efficiency of nitrobenzene was found to - catalyst dosage (g/l) = 1.0 g/l, 11202 : C6H5NO2 ratio = 7, pH = 3 and time = 5 h. At the optimum condition, average value of degradation efficiency (98%) in three confirmation experiments were close to predicted value for degradation efficiency was 97%. Taguchi methodology with four parameters namely catalyst dosage (gil), hydrogen - peroxide (1-1202) dosage (mmol), pH, and time (h) duration of reaction was used for optimizing dye degradation and colour removal efficiencies.The optimum condition for higher degradation efficiency was found to catalyst dosage = 1.25 g/l, H202 = 8 mmol, pH = 4 and time = 5 h. At the optimum condition, average value of degradation efficiency and colour efficiency was 58% and 78%. In three confirmation experiments was close to the predicted value for degradation efficiency and colour efficiency was 55% and 75% respectively. iv