In this paper, a novel hydrophobic modified cationic polyacrylamide flocculant P(AM⁃DAC⁃APG) was successfully synthesized by copolymerization of acrylamide (AM) as the main monomer, acryloxyethyl trimethyl ammonium chloride (DAC) as the cationic monomer and alkyl glycoside (APG) as the hydrophobic monomer, initiated by low⁃pressure ultraviolet light. FTIR, SEM and 1H⁃NMR were used to observe and analyze its chemical structure and surface morphology. The effects of other factors such as total monomer concentration and initiator concentration on the polymerization were studied. Optimum polymerization conditions were confirmed as total monomer concentration of 35.0%, initiator concentration of 0.2%, illumination time of 90 min, m（AM）/m（DAC）of 3, hydrophobic monomer concentration of 2.0%, urea concentration of 3.0%. The novel hydrophobic modified polyacrylamide flocculant with intrinsic viscosity and cationic charge density of 1 384.8 mL/g and 5.091 mmol/g was obtained under these conditions.

MnFe2O4/TiO2 Fenton⁃like photocatalyst was successfully prepared by sol⁃gel method, the structure and morphology of the sample were characterized by XRD, SEM and UV⁃vis. MB was used as the target pollutant for degradation, and the photocatalytic properties of products with different doping amounts were investigated in visible light. The results show that: The degradation rate of TMF Fenton⁃like photocatalytic reaction to MB is up to 96.8%, under the optimum conditions, in the iodine⁃tungsten lamp with a light source of 300 W, the doping amount of MnFe2O4 to TiO2 is 2%, the mass of catalyst is 60 mg, pH=11, and the concentration of H2O2 is 8 mmol/L . Under the same conditions, compare with the undoped pure TiO2, the catalytic performance of MnFe2O4/TiO2 for MB under visible light is significantly improved.

The cationic plugging agent of water base drilling fluid was prepared by emulsion polymerization with styrene (St), butyl acrylate (BA) and cationic polymerizable monomer. The structure characteristics of the plugging agent were analyzed by infrared spectrum. The result of soaking test with clay ball showed that cationic plugging agent emulsion with a mass fraction of 5.0% was equivalent in inhibiting clay hydration property of saturated brine. The effect of cationic plugging agent on the properties of CaCl2 free phase drilling fluid was evaluated. The results showed that the high temperature and high pressure filtration (120~130 ℃) could be controlled at about 10 mL for the non phase drilling fluid with CaCl2 content of 25.0% when the cationic plugging agent is 2.0%.