The adsorption and desorption behaviors of 17a-ethinylestradiol on various sludges derived from different treatment units of a sewage treatment plant were investigated using batch equilibration experiments. The results showed that adsorption process could be well described by pseudo-second-order kinetic model and fast adsorption played a main role. Adsorption ability varied as the order of aerobic sludge & anoxic sludge & primary sludge [ sludge cake [ anaerobic sludge. Adsorption/ desorption isotherms were well fitted by the modified Freundlich model, and K 0 f values increased with the organic matter content. Thermodynamic analysis indicated that 17a-ethinylestradiol adsorption/desorption was exothermic and conducted spontaneously. After heat treatment for removing the organic carbon, K 0 f values decreased by more than 78%, but organic carbon normalized adsorption constant was 7.76-29.51 mg/g. The 17a-ethinylestradiol adsorption capacity was found to decrease from 0.95-1.39 to 0.44-0.49 mg/g with sludge concentration increasing from 500 to 4,000 mg/L, being almost unchanged at pH 3-10 and sharply decreasing with pH [ 10. The adsorption capacity was also found to fluctuate in the range of 2.0-3.0 mg/g when Ca 2? concentration was \0.5 mol/L and increased rapidly above 0.5 mol/L. Addition of methanol and acetonitrile could improve 17a-ethinylestradiol desorption effect, which increased with the content of organic solvents, and the desorption degree of acetonitrile was higher than methanol.
The welding of thick high strength aluminum alloy plate was exceedingly difficult. Traditional arc welding was prone to softening the welded joints and involves multilayer; meanwhile, multi-pass welding may cause great residual welding stress, and deformation resulted in dampening the wide expansion of the welding structure of thick high strength aluminum alloy plates. Therefore, it was urgent to develop advanced materials and welding technologies to enhance the comprehensive mechanical properties of welded joints. Fiber laser boasted the advantages such as perfect monochromaticity and high quality light beam. In order to decrease the thermal loss of the welding heat source on the matrix, small power fiber laser and super narrow gap groove were applied for the effective welding of the 20-mm thick 7A52 aluminum alloy. The welding adopted multilayer and single pass welding with the groove width no wider than 4 mm. The weld was composed of four layers and the size was no wider than 4.5 mm, which was basically consistent with the widths of the whole. The parent metal was welded with 5183 alloy and 5E06 alloy. Fiber optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile testing machine were employed to investigate the influence of Er-Zr microalloying aluminum alloy welding wires upon the microstructure and mechanical properties of the welded joints.
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