Preparation of ZnO nanopowder by a novel ultrasound assisted non-hydrolytic sol–gel process and its application in photocatalytic degradation of C.I. Acid Red 249

Rod-like zinc oxide (ZnO) nanopowder was synthesized from zinc acetate via an ultrasound assisted non-hydrolytic sol–gel process. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–vis spectroscopy. X-ray diffraction confirmed that the as-prepared nanopowder was excellently crystallized. TEM images displayed the samples consisting of rod-like nanocrystallites of about 30 nm width and 50–70 nm length. A plausible nonhydrolytic alcoholysis route based on the well-known ester-elimination reaction that involved the nucleophilic attack of the hydroxyl group of diethylene glycol on the carbonyl carbon atom of zinc acetate was proposed and confirmed by gas chromatography–mass spectroscopy (GC–MS) analysis. Diethylene glycol not only acted as a solvent, but also acted as a reactant and as a capping agent, limiting particles growth and preventing their agglomeration. Photocatalytic degradation of C.I. Acid Red 249 (AR249) was carried out with synthesized ZnO nanopowder. The blank experiments showed that both UV illumination and the catalyst were necessary for the decomposition of AR249. The influences of various operational parameters such as catalyst dose, dye concentration, pH of the solution on percentage photodegradation of AR249 were investigated. The degradation of AR249 was found to be effective in alkaline media and the kinetic of photodegradation followed pseudo-first-order kinetic model. The rate constant for degradation of AR249 was calculated to be 0.01369 min− 1.