Nanobubbles (NBs) hold promise in green and sustainable engineering applications in diverse fields (e.g., water/wastewater treatment, food processing, medical applications, and agriculture). This study investigated the effects of four types of NBs on seed germination and plant growth. Air, oxygen, nitrogen, and carbon dioxide NBs were generated and dispersed in tap water. Different plants, including lettuce, carrot, fava bean, and tomato, were used in germination and growth tests. The seeds in water-containing NBs exhibited 6-25% higher germination rates. Especially, nitrogen NBs exhibited considerable effects in the seed germination, whereas air and carbon dioxide NBs did not significantly promote germination. The growth of stem length and diameter, leave number, and leave width were promoted by NBs (except air). Furthermore, the promotion effect was primarily ascribed to the generation of exogenous reactive oxygen species by NBs and higher efficiency of nutrient fixation or utilization.
Wetting and fouling phenomena are the main concerns for
membrane distillation (MD) in treating high-salinity industrial wastewater.
This work developed an omniphobic membrane by growing titanium dioxide
(TiO2) nanorods on polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) nanofibers using a hydrothermal technique.
The TiO2 nanorods form a uniform pine-needle-like hierarchical
nanostructure on PVDF-HFP fibers. A further fluorination treatment
provides the membrane with a low-surface-energy omniphobic surface,
displaying contact angles of 168° and 153° for water and
mineral oil, respectively. Direct contact MD experiments demonstrated
that the resulting membrane shows a high and stable salt rejection
of >99.9%, while the pristine PVDF-HFP nanofibrous membrane suffers
a rejection decline caused by intense pore wetting and oil fouling
in the desalination process in the presence of surfactant and mineral
oil. The superior antiwetting and antifouling behaviors were ascribed
to a nonwetting Cassie–Baxter state established by the accumulation
of a great deal of air in the hydrophobized hierarchical re-entrant
structures. The development of omniphobic membranes with pine-needle-like
hierarchical nanostructures provides an approach to mitigate membrane
wetting and fouling in the MD process for the water reclamation from
industrial wastewater.
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