Abstract
The aqueous extract of marine green macroalgae, Ulva fasciata Delile, was harnessed for the synthesis of zinc oxide nanoparticles (ZnO-NPs). The conversion to ZnO-NPs was characterized by color change, UV-vis spectroscopy, FT-IR, TEM, SEM-EDX, and XRD. Data showed the formation of spherical and crystalline ZnO-NPs with a size range of 3-33 nm. SEM-EDX revealed the presence of Zn and O in weight percentages of 45.3 and 31.62%, respectively. The phyco-synthesized ZnO-NPs exhibited an effective antibacterial activity against the pathogenic Gram-positive and Gram-negative bacteria. The bacterial clear zones ranged from 21.7 +/- 0.6 to 14.7 +/- 0.6 mm with MIC values of 50-6.25 mu g mL(-1). The catalytic activity of our product was investigated in dark and visible light conditions, using the methylene blue (MB) dye. The maximum dye removal (84.9 +/- 1.2%) was achieved after 140 min in the presence of 1.0 mg mL(-1) of our nanocatalyst under the visible light at a pH of 7 and a temperature of 35 degrees C. This percentage was decreased to 53.4 +/- 0.7% under the dark conditions. This nanocatalyst showed a high reusability with a decreasing percentage of similar to 5.2% after six successive cycles. Under the optimum conditions, ZnO-NPs showed a high efficacy in decolorizing the tanning wastewater with a percentage of 96.1 +/- 1.7%. Moreover, the parameters of the COD, BOD, TSS, and conductivity were decreased with percentages of 88.8, 88.5, 96.9, and 91.5%, respectively. Moreover, nano-ZnO had a high efficacy in decreasing the content of the tanning wastewater Cr (VI) from 864.3 +/- 5.8 to 57.3 +/- 4.1 mg L-1 with a removal percentage of 93.4%.