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How to sustainably produce bauxite by effective reverse froth flotation of kaolinite at low temperature is an urgent problem to be solved in the field of mineral processing. In this work, a novel amino-based Gemini surfactant butadiyl-1, 4-bis (dimethyl dodecylammonium bromide) (BBDB) was prepared and first utilized as a novel collector for kaolinite flotation. Its flotation performance for kaolinite was compared with that of the common monomolecular surfactant 1-dodecylamine (DDA) by micro-flotation tests. The tests results indicated that 95% kaolinite recovery was obtained using 2.0 × 10−4 mol/L BBDB at 25 ℃, which was half of the dosage when DDA obtained the maximum kaolinite recovery of 81%. At extremely low temperature (0 ℃), 3.0 × 10−4 mol/L BBDB could still collect 91% kaolinite, while DDA showed a frustrating ability. The contact angle tests indicated that BBDB could still significantly improve the hydrophobicity of the kaolinite surface (contact angle 71.7°) than DDA (contact angle only 25.8°) at 0 ℃. The Krafft point comparison tests indicated that BBDB had a much lower Krafft point (below 0 ℃) than DDA. Fourier transform infrared spectroscopy (FTIR)-spectrum analysis and zeta potential measurements showed that BBDB was physically adsorbed on the surface of kaolinite through electrostatic interaction.

In this study, a new hydroxamic-acid molecule - sebacoyl hydroxamic acid (SHA) was synthesized and characterized. It was the first time that SHA with dual hydroxamic acid groups of “crab” structure was used as a collector for wolframite flotation, and its collecting ability was compared with the traditional collector benzohydroxamic acid (BAH) in the presence or absence of lead ions. In micro-flotation experiments, the wolframite recovery using 4 × 10−4 mol/L SHA collector alone was 30% higher than that using 4 × 10−4 mol/L BHA collector and 1 × 10−4 mol/L Pb(NO3)2 activator. The results of bench-scale flotation experiments showed that the WO3 recovery of wolframite concentrate with 180 g/t SHA was 10.05% higher than that with 360 g/t BHA and 300 g/t Pb(NO3)2. Therefore, using SHA collector with “crab” structure for wolframite flotation can not only improve the separation index at a low dosage, but also eliminate the use of Pb(NO3)2.

This paper presents an approximate but efficient method for modeling the hydrodynamics and seakeeping performance of partial air cushion supported catamaran (PACSCAT) with planing demihulls. This method takes into account of the effects of the waves on the air–water interface under the air cushion induced by the pulsating pressure in the cushion and by the demihulls, which are ignored by existing approximate methods. Specifically, the new developments are made in two aspects. One is that the governing equations of the heave and pitch motions of the PACSCAT are derived to include the effects of the waves under the air cushion due to the pulsating pressure and the demihulls. Another one is that an approximate method is developed for evaluating the waves due to the pulsating pressure. Better agreement between the experimental data and the numerical results for pressure is achieved.

When a surface effect ship (SES) sails in waves, the unsteady velocity potential of water can be decomposed into incident potential, sidehull radiation potential, sidehull diffraction potential and radiation potential due to fluctuating air pressure. The potentials related to sidehulls satisfy Neumann boundary conditions (BC) and have been successfully addressed using the 2.5D method. In contrast, the potential related to fluctuating air pressure satisfies mixed BC consisting of homogeneous Neumann BC on the wetted surface of sidehulls and nonhomogeneous Dirichlet BC on the interface between air and water, which has never been studied using the efficient 2.5D method. In this paper, the 2.5D method is firstly proposed to solve the mixed boundary value problem (BVP), which can deal with the coupling between the fluctuating air pressure and sidehulls. By using the 2.5D method, the radiation wave and other relative hydrodynamic parameters of a SES due to the fluctuating air pressure are evaluated. The numerical results on motion response and the fluctuated air pressure of the SES show acceptable agreement with the experimental ones.

In froth flotation separation process, the collector molecular design has a crucial effect on potash processing to ensure sustainable production of potassium fertilizer (KCl) that is important to secure food supply in human society. Carnallite is an important source of KCl fertilizer production in industry. Reverse flotation has been used to separate halite (NaCl) impurities from carnallite (KCl·MgCl2·6H2O) for carnallite resources. However, progress in the carnallite resource reverse froth flotation has been constrained by the inherent limitation of traditional collector molecules with a single hydrophilic head and single hydrophobic chain per molecule. Herein, a novel morpholine-based Gemini molecule with double hydrophilic heads and hydrophobic chains, butanediyl-α, ω-bis (morpholino tetradecylammonium bromide) (BMTB) was synthesized and applied as the flotation collector in the reverse flotation separation for carnallite mineral. The better flotation performance of Gemini BMTB was achieved, compared to the traditional monomeric surfactant N-(n-Tetradecyl) morpholine (TDM). The bench-scale froth flotation separation results revealed that BMTB exhibited outstanding affinity and selectivity for NaCl crystals from carnallite at natural pH, resulting in less collector dosages – only 1/3 of TDM molecules. In contrast with traditional monomeric surfactant TDM (120 g/t), less amount of Gemini BMTB (40 g/t) – only one third of TDM molecules, was needed to obtain higher KCl recovery (KCl recovery raised by 4.69%). Meanwhile, the grade of NaCl with 40 g/t BMTB collector (2.19%) was lower than that with 120 g/t TDM collector (3.91%), and the grade of KCl with BMTB collector (22.59%) was higher than that with TDM collector (22.12%). Therefore, this work demonstrated the next-generation of flotation collector for the reverse froth flotation separation of the carnallite resources.

The partial air cushion supported catamaran (PACSCAT) is a type of air cushion assisted catamaran with planing demihulls. Both the air cushion and the demihulls can strongly affect the seakeeping performance. Although there exist some methods for analyzing the seakeeping of other air cushion supported vessels considering the effects of both the air cushion and demihulls, they can take considerable computational time. In this paper, an efficient numerical method is presented, which is formed by combining the 2.5D theory for solving hydrodynamics of demihulls with simplified wave-equation for solving aerodynamics of pressurized air to analysis the seakeeping performance of the high-speed PACSCAT. In the method, the cushion pressure is determined by using adiabatic gas law together with boundary conditions including the craft motion, free surface elevation, fan flows and air leakage. Two models are proposed for air leakage: constant leakage area and varying leakage area linearly related to ship motions and free surface elevation. The results obtained by the newly formulated method are compared with the experimental data, showing that the numerical results have reasonable agreements with experimental ones.

The Transformable-Craft (T-Craft) is an innovative vessel serving as a connector between sea base and beachheads. When operatingat seas, the T-Craft is a surface effect ship (SES) with compartmented air cushions. To analysis the seakeeping performance of the T-Craft SES, a high efficient 2D/2.5D analytical model has been developed by combining the one dimensional waveequation for solving aerodynamics of pressurized cushion air with the STF/2.5D method for solving hydrodynamics of demihulls at low/high speeds. To enhance the computational efficiency, the entire model is linearized except the dynamics of air leakage, which is strongly nonlinear and inappropriate for linearization. Results obtained from the proposed seakeeping analysis model show reasonable agreement with experimental data, while the proposed model hascompetitiveness in the computational efficiency as compared with some 3D models from public works.