Diffusion-controlled growth of CuAl₂O₄ nanoparticles: effect of sintering and photodegradation of methyl orange

Abstract

Facile synthesis of CuAl 2 O 4 and sintering effects on the phase composition are reported. Annealing at 500 C showed only CuO phase and the spinel phase started evolving at 700 C with the concurrent decrease in the CuO phase. Diffusion-mediated growth of spinel phase was also observed at higher temperatures forming CuAl 2 O 4 at 1000 C. The material was stoichiometric and the average particle size was 55 nm, as evidenced by EDS and FE-SEM studies, respectively. The zeta potential of C30 mV and lower (0.346) value of the poly dispersive index (PDI), confirmed the high dispersability of CuAl 2 O 4 in water. The favourable band gap (2.2 eV) makes it suitable as visible light photocatalyst. Owing to its positive surface charge and conducive pH, material could adsorb anionic methyl orange dye. A total of 74% of the dye could be recovered by a simple methanolic extraction. The visible light photocatalysis of the same dye leads to 67% decolouration and the addition of H 2 O 2 accelerated the photodegradation to completion. The catalyst displayed excellent reusability and stability even after five successive runs.

Reactive oxygen species‐induced heterogeneous photocatalytic degradation of organic pollutant Rhodamine B by copper and zinc aluminate spinels

“…The most satisfactory results were found for the conditions of 10 mg L −1 RhB concentration and 1 g L −1 of ZnAl 2 O 4 . These values demonstrated better performance because, in photocatalysis, a higher concentration of dye can inhibit light penetration capacity, making it not possible to reach and activate the photocatalyst …”

“…For semiconductor materials in catalytic applications, lower band gaps are of most interest, as they lower the minimum energy needed to be supplied to the reaction medium, making process costs feasible . Copper aluminate (CuAl 2 O 4 ) spinel, with a low band gap (1.77–2.3 eV) has been used as a potential UV and visible light photocatalyst in the degradation of toxic organic dyes . Zinc aluminate (ZnAl 2 O 4 ) spinel also has been cited in the literature as a promising photocatalyst for dye degradation …”

Cr‐doped ZnAl2O4: Microwave solution route for ceramic nanoparticles from metalorganic complexes in minutes

“…The present work demonstrates that microwave irradiation can be used to synthesize fine‐grained refractory oxides at temperatures as low as 220°C relatively quickly (40‐60 minutes), the rapidity stemming from the dielectric heating at the molecular level that leads to uniform heating and high local temperatures . Considering that the material is a ceramic, 220°C is quite low (compared to co‐precipitation method) for synthesizing crystalline material and much faster compared to other methods. In addition, the use of metalorganic precursors favors the formation of oxide materials through nucleophilic attack of solvent on the carbonyl group of the acetylacetonate ligand, the subsequent hydrolytic formation of metal hydroxide intermediates and their polycondensation to form the metal oxides.…”

“…The process requires high temperature and long reaction times, undesirable both from environmental and technological points of view. Therefore, wet chemical methods such as sol‐gel, combustion, co‐precipitation, and hydrothermal have been employed. In the sol‐gel method, the main disadvantages are the possibility of formation of multiphase materials and the long reaction time.…”

“…Though the hydrothermal process is a most promising method for preparing ceramic nanoparticles, the processing is time‐consuming and energy‐intensive. The pH‐dependent co‐precipitation method requires >10 hours at temperatures >500°C for the formation of spinel phase, making this process technologically disadvantageous and undesirable . Thus, there is a need for developing a swifter and more energy efficient method for the synthesis of oxide spinels.…”