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Recycling of valuable metals from spent catalysts in a green way is gaining extensive interest for economic and environment reasons. In this study, we developed novel hydrophobic deep eutectic solvents to extract Mo from spent catalysts. The hydrophobic DESs have been designed and synthesized by mixing one molar of the quaternary ammonium salt and two molars of various saturated fatty acids with different carbon chain lengths. The extraction ability and extraction mechanism of these DESs were studied, some factors influencing the extraction efficiency, including the structure of hydrogen bond acceptors and hydrogen bond donors, initial aqueous pH, reaction time and temperature, phase ratios were investigated. It is found that the synthesized hydrophobic DESs exhibit excellent extraction performance toward Mo, where the Mo distribution ratio is more than 2200 in the presence of other metals, corresponding to an extraction efficiency of 99% at optimal reaction conditions. This work reveals a distinct class of materials, guiding an effective and green way for spent catalyst treatment. Implications: Novel hydrophobic deep eutectic solvents have been developed to extract Mo from spent catalysts, the synthesized hydrophobic DESs possess several advantages, such as green, low price, low toxicity, and biodegradability. It exhibits excellent extraction performance under an optimized extraction condition. This work reveals a distinct class of materials, guiding a promising way for green and economical utilization of spent catalysts. [ABSTRACT FROM AUTHOR]

Ships have become an important source of SO2 emission in coastal areas with the rapid development of maritime transport. It is of great significance to develop a marine scrubber for reducing SO2 emission of ships. In this study, numerical simulation of a full-scale marine spray scrubber is conducted to investigate two-phase flow pattern and SO2 absorption process in the scrubber. A desulfurization model based on seawater absorbent is coupled into the simulation, which considers the mass transfer between phases and seawater aqueous phase chemistry simultaneously. A distribution ring is introduced in the scrubber to enhance the desulfurization performance of the scrubber. The result of simulation shows that the distribution ring can optimize effectively the distribution of gas–liquid phases and enhance the SO2 absorption. Under vertical condition, the desulfurization efficiency could be promoted approximate 6% after installing a distribution ring. The inclined condition resulting from the ship swinging could lead to the uneven distribution of droplets and an obvious decrease (8.7%) of desulfurization efficiency, whereas the desulfurization performance of the scrubber could be ensured with a distribution ring installed even under an inclined condition. Finally, a spray scrubber design scheme has been developed and successfully applied in the exhaust gas cleaning system (EGCS) of a container ship. Test result shows the outlet average value of SO2/CO2 can be reduced to 3.55. Meanwhile, the consistency of test data and calculation result indicates the applicability of the numerical model established for the simulation and optimization of the scrubber in industrial applications also. Implications: EGCS is an effective method to reduce SO2 emission of marine industry. However, different from a land desulfurization tower, the application of a spray scrubber in EGCS faces more problems due to the different application scenarios and complex sea conditions (inclined condition resulting from ships swinging and so on) during sailing. In this work, a numerical model capable of investigating physical and chemical phenomena in the scrubber simultaneously is established, which can produce a great amount of data for the operation instruction of EGCS and the design and optimization of the marine spray scrubber. The distribution ring is introduced in the marine spray scrubber to intensify the SO2 absorption and enhance the desulfurization performance of the scrubber under different working conditions. [ABSTRACT FROM AUTHOR]