Photodegradation of Rhodamine B catalyzed by ZnO pellets

Abstract

This paper describes the development of ZnO semiconductors applied as photocatalysts for the degradation of water contaminants, with the shape of ceramic pellets thick enough to maintain their structures, prepared by slip casting and sintering. The samples presented porosities around 40% and densities around 3.4 g/cm 3 , which represented about 61% of the theoretical density of ZnO. After obtaining the ceramic samples, the degradation of Rhodamine B dye by photocatalysis was evaluated in six cycles of degradation. After the cycles, changes in the surface of the samples were verified, possibly due to leaching during photocatalysis since they presented mean grain sizes of 0.61 μm before and 0.36 μm after the photocatalysis. The ceramic ZnO samples were able to satisfactorily degrade Rhodamine B for several cycles, resulting in successful reuse of photocatalysts and increased facility of removing the photocatalysts from the medium after degradation compared to powders in suspensions.

ZnO semiconductors obtained by slip casting: Application and reuse in photocatalysis

“…For this purpose, the slip (liquid mixture of ZnO particles and deflocculant suspended in water) was produced according to a mass ratio of 69.54% ZnO p.a. (28.00 g, Synth), 29.80% deionized water (12.00 g) and 0.66% deflocculant (0.265 g, Disperlan LA, Lamberti), which followed the mass deflocculant concentration of 6.58 × 10 −3 g deflocculant /g slip defined by previous studies 31 . The mixture (40.265 g) was added to a teflon vessel, with 8 mm diameter alumina ceramic grinding balls, with a 1:3 mass ratio of balls to slip, maintaining a ball:mass ratio between 20 to 30%.…”

“…(28.00 g, Synth), 29.80% deionized water (12.00 g) and 0.66% deflocculant (0.265 g, Disperlan LA, Lamberti), which followed the mass deflocculant concentration of 6.58 × 10 −3 g deflocculant /g slip defined by previous studies. 31 The mixture (40.265 g) was added to a teflon vessel, with 8 mm diameter alumina ceramic grinding balls, with a 1:3 mass ratio of balls to slip, maintaining a ball:mass ratio between 20 to 30%. Then, it was homogenized, for 30 min, using a high energy ball SPEX mill (SamplePrep 8000, 134 rcf).…”

“…However, after its use, it is necessary to apply complex procedures to separate the semiconductors, which generates additional costs to the catalytic process and an increase in wastewater treatment time. 29 The preparation and use, in photocatalysis, of immobilized semiconductors, [30][31][32][33][34][35][36][37][38] that is, in the form of thin films [39][40][41][42] or ceramic pieces, is advantageous, since the removal of the catalyst from the reaction medium is facilitated, in addition to the possibility of its reuse in other reaction cycles, thus ensuring greater financial viability in an industrial aspect.…”

“…The preparation and use, in photocatalysis, of immobilized semiconductors, 30–38 that is, in the form of thin films 39–42 or ceramic pieces, is advantageous, since the removal of the catalyst from the reaction medium is facilitated, in addition to the possibility of its reuse in other reaction cycles, thus ensuring greater financial viability in an industrial aspect.…”

Obtaining Porous Zinc Oxide Ceramics Using Replica Technique: Application in Photocatalysis

“…Porous ceramic pieces are produced through different processing routes [19][20][21][22][23][24][25][26][27][28] . Factors such as cost, ease of execution, and low waste generation can be the starting point for selecting the most appropriate processing method 22,23 .…”