A Molecular-Based Design of RGO/TiO2-PAM Composite Flocculant with Photocatalytic Self-Degrading Characteristics and the Application of the Oil Sand Tailings Flocculant

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.