Polymer flocculation technology has a very broad application in the flocculation industry of oil sand tailings at present. Nevertheless, the most commonly used commercial polyacrylamide flocculant has problems of low flocculation efficiency and secondary pollution. In this paper, we proposed an organic–inorganic composite flocculant with self-degrading properties for the flocculation treatment of oil sand tailings, which was prepared by a photocatalytic surface initiation technique. Further, the functional groups of the materials before and after polymerization composites were characterized by infrared spectrum to explore the polymerization mechanism, the structure was observed by transmission electron microscope, and the molecular weight of polyacrylamide was measured by gel permeation chromatography. Then, the flocculation performance was characterized by the flocculation experiment (tested with simulated oil sand tailings). Subsequently, the flocculation mechanism was explored by testing the zeta potential of the organic–inorganic composites and analyzing images of sediment observed by transmission electron microscope and atomic force microscope. Finally, the test of self-degradation performance was carried out under illumination. On the basis of the above experiments, the following conclusions were obtained. First, the structural characterization results indicate the polymerization mechanism is that, under the condition of light, the surface of the inorganic photocatalyst generates free radicals to initiate the radical polymerization of the monomers, so that the monomers successfully grow on the surface of the inorganic particles into a comb structure. And then, the flocculation experiment shows that reduced graphene oxide/titanium dioxide-polyacrylamide (2:40) has the best flocculation effect, of which the supernatant transmittance is 21.4 higher and the sedimentation ratio is 8.9% higher than those of the commercial polyacrylamide. The reason for its excellent flocculation performance is that the zeta potential of the organic–inorganic composite increases, reducing repulsion of particles and flocculant molecules; simultaneously, the formed comb structure is beneficial to the expansion of the polymer chain and increases the contact area, thereby improving the flocculation effect. Ultimately, the degradation results indicate that the new organic–inorganic composite had good degradation effect, with the degradation rate up to 75.9% within 4 h. Therefore, this work has made great contributions to solving the oil sand tailings pollution field.
To improve the catalytic efficiency of nanotitanium dioxide, this research investigated the phase transformation, crystal growth, and hydrogen production efficiency of nanotitanium dioxide at different temperatures and pressures. The RGO/TiO2 photocatalyst was prepared by a hydrothermal method using graphene oxide and butyl titanate as raw materials. Different types of photocatalyst samples were prepared by adjusting the reaction temperature and time in the hydrothermal process. X‐ray diffraction and transmission electron microscope techniques were employed to investigate the nucleation and growth processes of rutile and anatase in the hydrothermal process from the perspectives of thermodynamics and kinetics. The evolution of the titanium dioxide structure with hydrothermal temperature and hydrothermal time was analyzed. Finally, photocatalytic decomposition of water data shows that the photocatalyst with the best hydrogen production effect was obtained by 12 hr of hydrothermal treatment at a hydrothermal temperature of 180°C. The total hydrogen production of this sample was 0.037 mmol/g under a xenon lamp for 3 hr.
With the high precision and stability of its frequency signal outputs, active hydrogen maser plays an important role in such fields as timing, satellite navigation, and communication. However, it needs to be lighter so as to be applied in space. We made a research, based on the calculation of the hydrogen flow and the adsorption efficiency of the adsorption unit, on the parameters of the vacuum system and the structural requirements, and designed a combined vacuum pump for the Space Active Hydrogen Maser (SAHM). This vacuum pump consists of a getter pump and a small ion pump, the total mass of which is about 5 kg. The pumping speed will be about 474 L/s by computation, when an amount, 2.5 MPa L, of hydrogen has been adsorbed by getters. Theoretically, the total source hydrogen inflow in lifetime is not higher than 20% of the total capacity getter pump, thus the design should amply meet the requirements of the SAHM vacuum system, and is of great significance for future SAHM applications.
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