Hydrothermally Grown ZnO Nanostructures for Water Purification via Photocatalysis

Abstract

Semiconductor-based photocatalysis is a well-known and efficient process for achieving water depollution with very limited rejects in the environment. Zinc oxide (ZnO), as a wide-bandgap metallic oxide, is an excellent photocatalyst, able to mineralize a large scale of organic pollutants in water, under UV irradiation, that can be enlarged to visible range by doping nontoxic elements such as Ag and Fe. With high surface/volume ratio, the ZnO nanostructures have been shown to be prominent photocatalyst candidates with enhanced photocatalytic efficiency, owing to their being low-cost, non-toxic, and able to be produced with easy and controllable synthesis. Thus, ZnO nanostructures-based photocatalysis can be considered as an eco-friendly and sustainable process. This paper presents the photocatalytic activity of ZnO nanostructures (NSs) grown on different substrates. The photocatalysis has been carried out both under classic mode and microfluidic mode. All tests show the notable photocatalytic efficiency of ZnO NSs with remarkable results obtained from a ZnO-NSs-integrated microfluidic reactor, which exhibited an important enhancement of photocatalytic activity by drastically reducing the photodegradation time. UV-visible spectrometry and high-performance liquid chromatography, coupled with mass spectrometry (HPLC-MS), are simultaneously used to follow real-time information, revealing both the photodegradation efficiency and the degradation mechanism of the organic dye methylene blue.

Comparison of ZnO Nanoparticles Prepared by Precipitation and Combustion for UV and Sunlight-Driven Photocatalytic Degradation of Methylene Blue

“…These popular materials are often studied for their photocatalytic properties due to their wide bandgap energy (E g ) and high surface area resulting in efficient light absorption and enhanced catalytic activity, respectively. Among these, ZnO is a well-known multifunctional-semiconductor material that has been widely investigated for its usage as a photocatalyst [ 7 ] because of its good photocatalytic activity, low-cost material, and non-toxicity [ 8 , 9 , 10 ]. Importantly, suitable synthesis methods have been studied, such as microwave synthesis, laser-ablation, hydrothermal, sol-gel, precipitation, and combustion [ 11 , 12 , 13 , 14 , 15 ].…”

Preparation of functionalZnOnanoparticles and their application asUVphotosensitizer and reinforcing agent for waterborne polyurethane acrylate composite coating

“… where, hv is the value corresponding to photon energy, α is the value corresponding to absorption coefficient, A is the value corresponding to proportionality constant and n is the value that depends on the nature of transition ( n = 2 for direct band gap and 1/2 for indirect band gap). ZnO is a direct band gap semiconductor 34,35 and the Tauc plots were constructed with direct behavior. The figure shows that the banding energies of ZnO NPs‐C, ZnO NPs‐S, and ZnO NPs‐P are calculated to be 3.14, 3.20, and 3.12 eV, respectively.…”

Fabrication of a P–Si/ZnO heterojunction based on galvanic cell driven and the complete degradation of RhB via fast charge transfer

“…It has exceptional photoresponse capability and excellent photostability, effectively mitigating photo corrosion. [18][19][20][21] The combined use of P-Si and ZnO can promote the separation of electron-hole pairs at the interface, reduce recombination, increase the contact area with reactants, and improve light absorption capability and reaction rate. Rangelova et al 22 prepared a SiO 2 /ZnO composite material by the sol-gel method for photocatalytic degradation of malachite green.…”