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As an efficient flocculant, polyacrylamide (PAM) is widely used in water treatment process. The acrylamide monomer (AM) produced by depolymerization of residual PAM has been listed as a class IIA carcinogen, and its treatment is imminent. Flotation tailing (TC) was used as raw material to prepare a modified tailing matrix by alkali excitation. Nano-TiO2 was loaded onto the modified tailing matrix by hydrothermal method to prepare tailing-based nano-TiO2 composite (TiO2/TC) and Pb-doped tailing-based nano-TiO2 composite (Pb-TiO2/TC). The photocatalytic degradation properties of TC, modified coal matrix, TiO2/TC and Pb-TiO2/TC were analyzed with PAM as the target pollutant. The samples were characterized by XRD, SEM, UV-vis and BET, and the degradation products were analyzed and studied by high performance liquid chromatography-mass spectrometry. The degradation mechanism of PAM was explored. The results show that TC is irregular and the surface is rough; the surface of TiO2/TC is loose, the pore structure is obvious, and the fine tubular TiO2 is uniformly coated on the surface of modified tailings. The structure of Pb-TiO2/TC is more fluffy, and the modified coal matrix is loaded with more tubular TiO2. The band gap of TiO2/TC was 3.16 eV, and Pb2+ doping reduced the band gap of Pb-TiO2/TC to 3.08 eV. The specific surface area of TiO2 is 286.66 m2/g, the specific surface area of TiO2/TC and Pb-TiO2/TC are 360.33 m2/g and 358.54 m2/g. The higher specific surface area provides more active sites for the reaction, and the adsorption-catalytic synergistic effect significantly improves the photocatalytic efficiency. The degradation rates of PAM by TC and modified tailing matrix were 3.39% and 4.68%. The degradation rates of polyacrylamide by TiO2/TC and Pb-TiO2/TC loaded with TiO2 increased to 38.92% and 63.87%. After five cycles, the photocatalytic properties of TiO2/TC and Pb-TiO2/TC remained basically unchanged. In the degradation process of PAM, the macromolecular PAM breaks into small molecular weight PAM molecules, and further decomposes into NO3−, acrylic acid, acetamide and acetic acid.

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