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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.

Electrochemistry has the advantages of low detection limit, high sensitivity, short analysis time, and convenient operation. It is an effective method for rapid detection of heavy metal ions in environmental samples. In this paper, humic acid-based activated carbon was prepared by chemical activation of humic acid extracted from lignite. The carbon paste electrode was doped with humic acid-based activated carbon, and the stripping voltammetry characteristics of Cd(Ⅱ) on the modified electrode were studied by anodic stripping voltammetry. The research shows that the doping of humic acid-based activated carbon on carbon paste electrode improved the response of Cd(Ⅱ) on the electrode, thus improving the sensitivity, expanding the linear detection range, and reducing the detection limit. When the activated carbon was used for chemical modification of carbon paste electrode a high content of oxygen-containing functional groups and a large pore size, were beneficial to improving the response of Cd(Ⅱ) on the electrode and improving the sensitivity of the electrode. All the carbon paste electrodes doped by humic acid-based activated carbon exhibited good repeatability and long-term stability.

In wet coal preparation, the products of some processes are transported as low-concentration suspensions. Their rheology is greatly affected by the properties of the coal particles that result from the formation and weathering during preparation. In this study, the properties of coal particles, including volumetric properties (i.e., solids content, granularity, and clay mineral fraction) and surface characteristics (i.e., dynamic potential, degree of coalification, and degree of surface oxidization), were studied to determine their effects on the apparent viscosity of low-concentration coal suspensions. With increasing solids content and smaller particle size in the suspension, the interactions between the coal particles became stronger due to the increased particle content, thus increasing the coal suspension's apparent viscosity. Adding clay minerals to the suspension gradually changed its composition and structure and increased its viscosity. The dynamic potential of the coal particles and inter-particle electrostatic repulsive forces were reduced with the addition of Ca2+ ions, and the coal particles collided and aggregated, which increased the apparent viscosity of the suspension. For coal with a low degree of coalification or coal had been oxidized by a hydrogen peroxide solution, the suspension of the hydrophilic coal particles was associated with a lower apparent viscosity than that of highly hydrophobic solids, which tended to aggregate and form flocculent masses. [ABSTRACT FROM AUTHOR]