In
this work, the calcined chitosan (CS)-supported layered double
hydroxides were prepared, characterized, and further applied to remove
organic contaminants in aqueous solution. The chitosan-supported layered
double hydroxide calcined at 400 °C (CSLDO400) was found to be
effective for the adsorption of azo dye and antibiotic. CSLDO400 showed
excellent adsorption performance at a wide pH range from 5 to 9 for
methyl orange (MO) while the adsorption of tetracycline (TC) was most
efficient at a pH of 9, and the optimal CSLDO400 dosages were 0.175
g L–1 for MO and 0.375 g L–1 for
TC. The divalent and trivalent anions have a great effect on removal
efficiency of MO and TC, while the effect of monovalent anions adsorption
can be neglected. The adsorption kinetics indicated that the MO and
TC removal followed the pseudo-second-order model. In addition, it
can be fitted well with both the Langmuir and Freundlich model for
MO and TC at 298 K, respectively. The adsorptions of MO and TC on
CSLDO400 were both spontaneous and endothermic. After five adsorption–desorption
cycles, CSLDO400 still showed high efficiency with an adsorption capacity
of 60.72 mg g–1 for MO and 21.92 mg g–1 for TC. Therefore, the CSLDO400 are promising for use in the treatment
of drinking water and wastewater contaminanted by organic matters.
The oscillation arc assisted by an extra alternating longitudinal magnetic field (LMF) in narrow gap tungsten arc welding is proved to be effective in avoiding welding defects due to insufficient fusion at the side walls in joining thick wall plates. The behavior of the welding arc and molten pool under the LMF is simulated to reveal the influence of the LMF on the formation of a uniform penetration weld bead. A unified mathematical model was developed for the narrow gap tungsten arc welding including the plasma arc, molten pool, electrode, and their interactions. Under the LMF, the whole welding arc is deflected and oscillates between the two side walls. When the magnetic-field strength is larger than 6 mT, the axis of the arc deflects to the side wall; the maximum value of heat flux at the bottom decreases by one-half, and the maximum value at the side wall is increased by a factor of ten. On the other hand, under the LMF, the forces acting on the molten pool are changed; the fluid flow pattern is helpful to increase the heat transferred to the side walls. The model is validated by experimental results. Both the percentage deviations of the simulation weld penetration at the side wall and at the bottom from the experimental results are lower than 10%.
There are many soft-rock roadway coal mines in China. The surrounding rocks of the high-stress soft-rock roadways in deep mine are especially difficult to be supported using the traditional supporting way. In this study, the south wing rail roadway on the second level of Yunjialing coal mine in China was used as an example to analyze the deformation and failure characteristics and influencing factors of roadway. On this basis, this study proposed the equalized yielding support idea which employs the yielding rings to realize the pressure equalization on the bolts and cables in the section. To achieve this purpose, the first bolt-mesh-cable equalizing pressure yielding support was integrated with the second grouting reinforcement. The results proved that the yield rings of the bolts and cables on the spandrel of the arched roadway firstly developed yielding deformation; then the deformation extended to the vault of the roadway; the bolts and cables achieved a yielding extreme value of 15 and 18 tonnes, respectively. The roadway surrounding rock tended to be stable at the 26th day after the maintenance. The equalizing pressure yielding supporting technology plays a moderate pressure-releasing and actively controlling role on the surrounding rocks in the soft-rock roadway with large deformation.
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