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Superhydrophobic and superoleophilic meshes have attracted great attention in oil/water separating application. However, superhydrophobic surfaces are not only complicated in ...preparation but also easy to break in practical applications. In this paper, we prepared fluorine-free hydrophobic hexadecyltrimethoxysilane (HDTMS)-TiO2 coated meshes with properties of cost-effectiveness, easy to manufacture, and high separation efficiency by a liquid phase deposition method. The surface topography, composition, and functional groups of the meshes were characterized by field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform microscopic infrared spectrometer (FT-IR) spectrum, respectively. A new gravity-driven oil/water separator was designed for the separation experiments. The separation efficiency of the hydrophobic HDTMS-TiO2 coated meshes maintained over 97.8% after 35 separating cycles. This study indicated that the superhydrophobicity of the separating mesh was nonessential for the highly efficient oil-water separation. The fluorine-free hydrophobic HDTMS-TiO2 coated meshes provided an economical and beneficial solution to treat industrial oily wastewater mixtures and environmental oil spills.
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•Superhydrophobic meshes covered with nanostructured FAS grafted electroless Ni-P plating coating were prepared.•The meshes can rapidly and continuously separate oil-water mixture ...without any extra driving force and chemical agent.•The superhydrophobic mesh is steady and reliable for the long-term separation of the water-oil mixture.•A separation model of water-oil mixture through the superhydrophobic or hydrophobic meshes was proposed.
The development of the super-hydrophobic coating/film mesh for directly separating oil from water is greatly desired due to the high separation efficiency and the steady recyclability. Here we describe a facile and inexpensive method for fabricating the super-hydrophobic/super-oleophilic stainless steel meshes with the FAS modified electroless Ni-P composite coatings. The Ni-P particles on the mesh are spherical with a uniform size diameter and relatively concatenate each other to form a nanoscale rough surface. The static contact angles of the as-prepared meshes fall in between 124.4 ± 1.5° and 167.9 ± 2.1°. These meshes exhibit non-sticking of water, anti-fouling, and excellent penetrating through the oil properties. The prepared meshes can rapidly and continuously separate water-oil mixture without resorting to any extra driving force and the chemical agent. The best separation efficiency is 96.8%. The super-hydrophobic mesh is steady and reliable for a long-term separation of the water-oil mixtures. Finally, a separation mechanism of the super-hydrophobic meshes for the water-oil mixtures is proposed. We anticipate that the prepared meshes could provide a candidate application to effective waste oil cleanup and other rapid water-oil separation processes.
The paper presented an efficient integrated physicochemical process, which consists of chemical precipitation and air stripping, for the simultaneous removal of NH
3-N, total P and COD from ...anaerobically digested piggery wastewater. In the integrated process, Ca(OH)
2 was used as the precipitant for NH
4
+, PO
4
3− and organic phosphorous compounds, and as the pH adjuster for the air stripping of residual ammonia. The possibility of the suggested process and the related mechanisms were first investigated through a series of equilibrium tests. Laboratory scale tests were carried out to validate the application possibility of the integrated process using a new-patented water sparged aerocyclone reactor (WSA). The WSA could be effectively used for the simultaneous removal of NH
3-N, total P and COD. 3
g/L of Ca(OH)
2 is a proper dosage for the simultaneous removal. The simultaneous removal of NH
3-N, total P and COD in the WSA reactor could be easily optimized by selecting a proper air inlet velocity and a proper jet velocity of the liquid phase. In all the cases, the removal efficiencies of the NH
3-N, total P and COD were over 91%, 99.2% and 52% for NH
3-N, total P and COD, respectively. The formed precipitates in the process could be easily settled down from the suspension system. Therefore, the integrated process provided an efficient alternative for the simultaneous removal of NH
3-N, total P and COD from the wastewater.
Micro-EDM technology is widely used in the field of micro-fabrication due to its low cost, non-contact, and other processing characteristics. The EDM method involves molding parts by implementing the ...principle of melting metal at a high temperature, which results in a thin recast layer on the surface of the workpiece. The recast layer can critically affect the surface topography and mechanical properties of the part, making it a potential safety hazard in fields such as aerospace and medical sciences. The purpose of this paper is to apply the electrolytic removal method of the recast layer on different microstructures, and thus solve the problem of on-line, orientation, and quantitative removal of recast layers on complex three-dimensional surfaces. In this work, the main components of the recast layer were analyzed to push the main principles and influencing factors of its participation in the electrolytic reaction. Then, the electrolysis removal experiments of the recast layer on the surface of foundation structures were carried out, and different processing strategies were proposed for different microstructures. Finally, the micro-EDM-ECM–integrated processing technology was applied, resulting in a micro-grooved structure of surface roughness Ra less than 0.3 μm.
Technologies for remediation of wastewater by industrial solid waste have recently attracted interest. Acid mine drainage is an extraordinarily acidic and highly heavy metal ions contaminated ...leachate which posed some challenges for the environment. Nonetheless, steel slag shows significant potential application prospects in wastewater treatment, due to its excellent physicochemical properties and structures. This paper elaborately reviewed the structure, properties, water treatment applications of steel slags, and the mechanism for removing heavy metal ions from acid mine drainage, discussed the problems existing in industrial wastewater treatment by steel slag, and proposed the solutions for future research, aiming to provide theoretical references for the practical application of steel slag in AMD treatment.
Air stripping of ammonia is a widely used process for the pretreatment of wastewater. Scaling and fouling on the packing surface in packed towers and a lower stripping efficiency are the two major ...problems in this process. New equipment that is suitable for the air stripping of wastewater with suspended solids has been developed. Air stripping of ammonia from water with Ca(OH)
2 was performed in the newly designed gas–liquid contactor, a water-sparged aerocyclone (WSA). WSA exhibited a higher air stripping efficiency and an excellent mass transfer performance, it also consumed less air compared with stripping tanks and packed towers. In addition, no scaling and fouling was observed in the inner structure of the WSA. During the stripping process, the stripping efficiency and mass transfer coefficient naturally increases with the liquid phase temperature and air flow rate. There is a critical value for the air flow rate over which stripping efficiency and the mass transfer coefficient increases rapidly. An efficient air stripping of ammonia should be conducted at a higher ambient temperature (>25
°C), and a higher air flow rate (>1.4
l/s).
In the liquid phase oxidation leaching process of chromite salt, a new dynamic-static combined stirred mode is proposed. That is, a static cylindrical baffle is fixedly installed at a certain radius ...from the stirred blade to control the vicinity of the blade. The CFD numerical simulation method is mainly used to investigate the effect of dynamic-static combined mode on the flow field distribution. Meanwhile, the velocity distribution and trailing vortex near the blade are analyzed. Finally, the differences between traditional stirred blade and dynamic-static combined stirred blade in the oxidation leaching process of chromite are compared. The results show the new dynamic-static combined stirring mode can effectively improve the flow field distribution, reduce the occurrence of “dead zones” in the flow, and increase the chromite leaching efficiency. The leaching time can be reduced from 300 to 240 min, and the chromium-leaching rate has reached up to 99%.
Biologically-treated municipal solid waste （MSW） leachate still contains many kinds of bit-recalcitrant organic matter. A new plate and frame electrochemical reactor was designed to treat these ...materials under flow conditions. In the electrochemical oxidation process, NH3 and color could be easily removed by means of electro-generated chlorinefaypochlorite within 20 min. The effects of major process parameters on the removal of organic pollutants were investigated systematically. Under experimental conditions, the optimum operation parameters were current density of 65 mA/cm^2, flow velocity of 2.6 cm/sec in electrode gap, and initial chloride ion concentration of 5000 mg/L. The COD in the leachate could be reduced below 100 mg/L after 1 hr of treatment. The kinetics and mechanism of COD removal were investigated by simultaneously monitoring the COD change and chlorine/hypochlorite production. The kinetics of COD removal exhibited a two-stage kinetic model, and the decrease of electro-generated chlorine/hypochlorite production was the major mechanism for the slowing down of the COD removal rate in the second stage. The narrowing of the electrode gap is beneficial for COD removal and energy consumption.
The efficacious treatment and resource utilization of the chromite ore processing residue (COPR) is important for chromate salt production. In this study, the leaching of valuable elements from the ...waste COPR was investigated. X-ray diffraction (XRD) analysis showed that the COPR mainly contained periclase (MgCr2O4), magnesiochromite ((Fe, Mg) (Cr, Fe)2O4), Fe (Cr, Al)2O4, and MgFeAlO4. The optimum parameters for COPR leaching were as follows: mechanical ball-milling time of 120 min, sulfuric acid concentration (w/w % H2SO4) of 60%, reaction temperature (T) of 403 K, liquid–solid ratio (L/S) of 8 mL/g, and reaction time (t) of 6 h. Under these conditions, the valuable components such as Fe, Al, and Cr were extracted with an ideal leaching efficiency of 94.8, 75.1, and 76%, respectively. The results of the leaching kinetics analysis indicated that the leaching of Fe and Cr from the COPR was controlled by a surface chemical reaction, and the leaching of Al was controlled by diffusion through a product layer. The apparent activation energy of the leaching of Fe, Cr, and Al was calculated to be 23.03, 44.15, and 17.54 kJ/mol, respectively. It is believed that this approach has potential applications for the chromate salt industry because of its advantage of ideal leaching efficiency.
An original ultrasound (US) directly intensified photocatalytic reactor was designed to degrade azo dye pollutant methyl orange (MeO) using Degussa TiO2 as the photocatalyst. The sonolytic, ...photocatalytic and sonophotocatalytic degradation of MeO in the new reactor and the synergistic effect between sonolysis and photocatalysis were investigated. Effects of operation parameters i.e., US power, TiO2 dosage, liquid circulation velocity and air flow rate on degradation efficiency were investigated and optimized. The results showed that all parameters have optimal values for the sonophotocatalytic degradation of MeO, and the optimum conditions for the new process are US power 600W, TiO2 dosage 3g/L, liquid circulation velocity 4.05×10−2m/s and air flow rate 0.2L/min. Under the optimum conditions, 91.52% MeO had been degraded within 1h, and the combination of sonolysis and TiO2 photocatalysis exhibited an obvious synergetic effect.
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