Investigation of reductive degradation of azo dye methyl orange using hollow metal nanoparticles

In this thesis an efficient method for azo dye methyl orange (MO) degradation using as-synthesized hollow metal nanoparticles (NP) is presented. Hollow metal NPs of Co, Ni and Fe are fabricated through galvanic replacement strategy with Al nano-powders as the template material. The as-synthesized NPs of Co and Ni have a specific surface area of 57.6 and 28.8 m2 g -1. The degradation efficiency of MO is evaluated by studying the effects of two important factors including initial pH of the dye solution and metal NP dosage. The degradation characteristics and kinetics are investigated by measurement of the absorption of the dye solution with a UV-Vis spectrophotometer. With the variations in the MO absorbance intensity and formation of new absorbance band, degradation mechanism is discussed as well.;Kinetic studies revealed that the MO degradation by the as-synthesized hollow Co, Ni and Fe NPs appeared to be first-order with respect to the dye concentration. Among these three metal NPs, Co exhibited the highest degradation efficiency. Experimental studies on these Co NPs indicated that degradation rate and efficiency increased with a decrease in pH and an increase in NP dose. At pH 2, the degradation efficiency was up to 99% within 10 min at an initial MO conc. of 100 mg L-1 and Co NP dosage of 0.5 g L -1. At Co NP dosage of 1 g L-1, the degradation efficiency was up to 95% within 30 min at an initial MO conc. of 100 mg Land pH of 3. Reductive degradation by these hollow Cobalt NPs is a very promising approach for the remediation of azo dye containing waste water due to the fast degradation rate and high degradation efficiency. In addition, these hollow Co NPs are easy to be recycled because of their magnetic property.