Synthesis of TiO2@ZnO heterojunction for dye photodegradation and wastewater treatment

The presented work aims to synthesis and engineering a semiconductor-semiconductor (S–S) heterojunction with low bandgap energy. The synthesized material composed mainly from titanium dioxide (TiO) and zinc oxide (ZnO) as a photocatalytic nanoparticle (NPs). This strategy could highly enhance photo-degradation properties and antibacterial properties for wastewater treatment. A composite cellulose acetate CA@TiO NPs (CTO) was fabricated via electrospinning technique to generate a core TiO NPs within a polymeric matrix followed by immersion in ZnO NPs suspension solution to deposit ZnO NPs on the nanofiber surface (CTZO). Subsequently, the composite mat was subjected to a calcination/annealing process at 700 °C for 4 h to obtain composite S–S heterojunction nanostructure material (TZO). The morphological characteristics, thermal degradation, chemical composition, and phase structure of the synthesis material were investigated. In addition, antibacterial properties were evaluated using E-coli bacteria, whereas the photocatalytic degradation efficiency was performed using both methylene blue (MB) and methylene red (MR) dyes under direct sunlight. The morphological properties showed that TiO NPs was well decorated with ZnO NPs and form heterojunction structure. The resulted (TZO) has high antibacterial effect and showed a 15±0.8 mm of inhibition zone in gram (-ve) Bactria comparing to that of ZnO NPs (12±0.2) mm. Furthermore, photocatalytic degradation of the composite NPs showed high photodegradation properties close to 25% and 13% for MB and MR dyes in direct sunlight, respectively. The increased dye photodegradation is attributed to the formation of S–S heterojunction structure with low bandgap energy (1.17 eV) comparing to that of wide band gap energy (3.52 eV) of TiO that play role in enhancement of electron transfer and thus photodegradation process. These results suggest that the resulted S–S heterojunction nanomaterial have a high potential in wastewater application.