Zinc Oxide Nanoparticles Obtained by Supercritical Antisolvent Precipitation for the Photocatalytic Degradation of Crystal Violet Dye

Abstract

In this work, the synthesis of zinc oxide (ZnO) photocatalyst from thermal decomposition of zinc acetate (ZnAc) nanoparticles obtained by supercritical antisolvent (SAS) precipitation was investigated. The optimization of calcination conditions of the SAS ZnAc was carried out, studying the effect of temperature (in the range 300–600 °C) on the production of ZnO nanoparticles. In particular, it was demonstrated that the organic residues in ZnO and its particle size, thus the specific surface area, strongly affect the photocatalytic performances. SAS micronization of ZnAc produces regular nanoparticles with a mean diameter of about 54.5 ± 11.5 nm, whereas unprocessed ZnAc is characterized by very large crystals. The experimental results evidenced that ZnAc prepared by SAS process calcined at 500 °C showed a regular nanometric structure (mean diameter: 65.0 ± 14.5 nm) and was revealed to be the best choice for the photocatalytic removal of crystal violet dye (CV). In fact, the photocatalytic activity performances of ZnO nanoparticles prepared by this route were higher with respect to that of ZnO from unprocessed ZnAc calcined at 500 °C (which is characterized by irregular tetrapods with mean size 181.1 ± 65.5 nm). The optimized photocatalyst was able to assure the complete CV decolorization in 60 min of UV irradiation time and a mineralization degree higher than 90% after 120 min of treatment time.

Fabrication, functionalization and performance of doped photocatalysts for dye degradation and mineralization: a review

“…There are other recent studies which have equally highlighted the outstanding photocatalytic properties and exceptional photocatalytic dye degradation capabilities of catalyst materials synthesized using precipitation-based methods, such as the works of Kundu and Mondal (2019) where layered sodium-intercalated Cu-doped titania was fabricated employing controlled precipitation and then examined in malachite green photodegradation, Franco et al (2019) whereby ZnO photocatalyst was prepared through the thermal decomposition of zinc acetate NPs produced by a supercritical antisolvent precipitation method and then tested for its potential in the photocatalytic elimination of Crystal violet, Andrade Neto et al 2020where Ce 4+ -, Co 2+ -, Mn 2+ -and Ni 2+ -doped Fe 3 O 4 NPs were synthesized using co-precipitation at 70 °C and assessed for their potential in bringing about discoloration of methylene blue containing solutions, and last but not least, Munawar et al 2020wherein ternary oxide NiO-CdO-ZnO nanocomposite was synthesized following a homogeneous co-precipitation procedure and then tested for its sunlight-driven photocatalytic degradation ability of rhodamine B and methylene blue.…”

Supercritical Carbon Dioxide-Based Processes in Photocatalytic Applications

“…Up to now, the Supercritical AntiSolvent (SAS) precipitation was widely used to produce nanoparticles of different materials, including metal-based compounds to produce catalysts [ 66 , 67 , 68 , 69 ] and photocatalysts [ 42 , 43 , 44 , 45 , 46 ] with very high activity and selectivity performance for various reactions.…”

“…Then, the as-prepared precursor particles have to be usually calcined at high temperatures to produce the final oxide photocatalyst. Isopropanol, dimethylsulfoxide (DMSO), ethanol and methanol are usually selected as the proper solvents for the precipitation of photocatalyst precursors [ 42 , 43 , 44 , 45 , 46 ].…”

“…The semi-conductive photocatalysts generally used are titanium dioxide or titania (TiO 2 ) [ 21 , 22 , 23 ], ZnO [ 24 , 25 ], WO 3 [ 26 , 27 ], Fe 2 O 3 [ 28 , 29 ], CeO 2 [ 30 , 31 ], MoO 3 [ 32 , 33 ], ZrO 2 [ 34 , 35 ], SnO 2 [ 36 , 37 ], CdS [ 38 , 39 ], and ZnS [ 40 , 41 ]. Up to now, semiconductor-based photocatalysts in various forms have been proposed, mainly as nanopowders [ 42 , 43 , 44 , 45 , 46 , 47 , 48 ] or aerogels [ 49 , 50 , 51 , 52 , 53 , 54 ], due to the high specific surface area of these materials, resulting in a very high contact between the semiconductor and the fluid to be treated and, consequently, the photocatalytic performance could be enhanced.…”

Enhancing Photocatalytic Activity of ZnO Nanoparticles in a Circulating Fluidized Bed with Plasma Jets

“…Among various semiconductors, zinc oxide (ZnO) with the wide band gap (3.37 eV) [4], large exciton blinding energy (60 meV) [5], good photoelectric properties, non-toxicity, abundance and environmental stability [6,7] perform much better than other photocatalysts. Therefore, ZnO has been widely researched for various applications including photocatalysts [8][9][10], chemical sensors [11], transparent electrodes [12], solar cells [13] and luminescent materials [14,15]. Especially, ZnO performs well on the photocatalytic.…”