Abstract
Interfacial nanobubbles can exist on various hydrophobic and hydrophilic material interfaces. There are diverse applications for oxygen nanobubbles, which are closely related to their content and long-term stability. However, it remains challenging to determine the amount of nanobubbles loaded in a porous material. In this study, a novel method was used to quantify the total amount of oxygen nanobubbles loaded onto irregular particulate materials. Different materials were evaluated and their oxygen-loading capacities were found to be as follows: activated carbon (AC) > zeolite > biochar > diatomite > coal ash > clay. Significant differences in oxygen-loading capacities were mainly ascribed to differences in the specific surface area and hydrophobic/hydrophilic properties of the materials. The total oxygen loading on AC achieved using the high pressure loading method was higher than that achieved by the temperature variation method. This new quantitative method provides the possibility for the manipulation of oxygen nanobubble materials in practical applications and it is anticipated to be an important supplement to the existing methods of characterizing interfacial oxygen nanobubbles. Our results demonstrate that materials containing oxygen nanobubbles can significantly increase the dissolved oxygen and oxidation reduction potential in anaerobic systems. With the addition of oxygen-loaded materials (such as AC), the survival time of zebrafish was prolonged up to 20 h in a deoxygenated water system, and the germination rate of Vallisneria spiralis was also increased from 27 to 73% in an anaerobic sediment.