Heavy metal pollution to aqueous media is an important issue for environmental sustainability. A simple strategy for the synthesis of an efficient adsorbent is strongly desired for water remediation. Herein, aminopyridine functionalized magnetic Fe3O4 (HO–Fe3O4@ SiO2–AP) with excellent adsorption capacity and selectivity was synthesized by a feasible one-pot sequential reaction. As a comparison, the same adsorbent was also prepared by the general step-by-step surface modification method. The structure characterization and adsorption performance prove the efficiency of this strategy. The factors that affect the adsorption were determined. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Density Functional Theory calculation were used to demonstrate the adsorption mechanism. As HO–Fe3O4@SiO2–AP exhibits competitive adsorption capacity and excellent adsorption selectivity, it can be used potentially for robust removal, preconcentration, and recovery of aqueous Hg(II) and Ag(I).
Two novel highly efficient polymer composite adsorbents based on 3-chloropropyltriethoxysilane-grafted waste para-aramid (PPTA-CP-AT and PPTA-CP-L, PPTA=poly-p-phenylene terephthamide; CP = 3-chloropropyltriethoxysilane; AT=amino trimethylene phosphonic acid; L=L-proline) have been successfully prepared and characterized. The new adsorbents were synthesized by functionalizing 3-chloropropyltriethoxysilane-grafted waste para-aramid with amino trimethylene phosphonic acid and L-proline, respectively. They have been employed to adsorb gold ions from aqueous solution, and the relevant adsorption behaviors have been investigated in detail. The adsorption isotherms of PPTA-CP-AT and PPTA-CP-L were consistent with the Langmuir isotherm model, and the corresponding kinetics could be best described by the pseudo-second-order kinetic model. In particular, the adsorption capacity of PPTA-CP-L was much higher than the values reported in the literature. In addition, the effect of pH on the gold ions adsorption and the thermodynamic parameters of the adsorption procedure were assessed. The research results indicated that PPTA-CP-AT and PPTA-CP-L are two novel adsorbents with high efficiency in wastewater treatment and recovery of precious gold. In particular PPTA-CP-L, which was obtained through facile esterification synthesis at low temperature, showed an excellent adsorption performance and could be used as potentially excellent adsorbent for gold uptake.
In this study, plasma nitriding and multi-arc ion plating techniques were employed to enhance the load-bearing capacity of the TC4 alloy. The tribological properties were characterized, and the mechanisms were discussed in detail. Subsequently, the tribological properties of the coating enhanced with MoS2 were then evaluated, and the results indicated that the plasma nitriding treatment, which exhibited optimal friction performance, resulted in the formation of a nitrided layer with a thickness of 98 μm on the surface of the TC4 alloy, thereby significantly improving its mechanical properties. Furthermore, the TiN coating samples treated with plasma nitriding demonstrated superior mechanical properties, achieving the highest hardness value (20 GPa), high load-carrying capacity (58 N) and the lowest wear rate (9.16 × 10−6 mm3·N−1·m−1). Moreover, the tribological properties of MoS2 deposited on the surface of the PN-2/TiN sample were significantly enhanced, which can be attributed to the synergistic effect of the excellent load-bearing characteristics of the plasma nitriding treatment and the wear resistance of the TiN layer. This study investigates the factors contributing to the superior tribological performance of the PN-2/TiN sample and the extended friction lifetime of the PN-2/TiN/MoS2 sample. The composite coating provides a new method to improve the anti-friction of soft metals, especially titanium alloys, and is expected to be applied in the aerospace field.
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