Shaohua Ju

Microfluidic solvent extraction and separation of cobalt and nickel

The extraction and separation of cobalt from sulphate solution containing Ni2+ and Co2+ by the process of microfluidic extraction was investigated on a counter-current flow interdigital micromixer with channels of 40 μm width, which has two opposite inlets and an upwards outlet. Meanwhile, the comparative batch extraction experiments were conducted in separatory funnels. The effects of pH and flow rates or contact time on the microfluidic and batch experiments were studied using an aqueous solution containing 73.09 g L−1 of nickel and 2.44 g L−1 of cobalt and 20 vol% PC88A diluted with 260# solvent naphtha. In addition, cobalt extraction isotherms (Mc-Cabe Thiele) were constructed to determine the number of stages. The results of percentage extraction and separation factor of microfluidic extraction was better than that of batch extraction. The features of the microreactors, i.e. large specific surface area and short diffusion distance were effective for the efficient extraction and separation of cobalt from nickel.

Solvent extraction of Nd(III) in a Y type microchannel with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester

Abstract Conventional extraction equipment has many problems like a long mixing time, a large factory area occupation, a large amount of organic solvent consumption and so on. In this paper, a micro solvent extraction system for the extraction of Nd(III) was investigated to solve the above issues. The initial aqueous pH 4.0 and saponification rate 40% of 2-ethylhexyl phosphoric acid-2-ethylhexyl ester (P507) were selected as the optimal experimental conditions. The extraction equilibrium was quickly achieved within 1.5 s, without any mechanical mixing in a narrow channel (100 μm in width and 120 μm in depth) at a volumetric flow rate from 5.55×10-10 m3/s to 1.53×10-9 m3/s. The extraction behavior of Nd(III) in the microreactor is an interface chemical reaction or the diffusion rate of the Nd-complex in the organic phase at low pH and [P507], while the extraction rate is controlled by the rate of metal diffusion in the aqueous phase at high pH and [P507], and the apparent mass transfer rate is up to 3.29×10-5 mol/m2·s. The extracted complexes are determined by the infrared (IR) spectrum method, and confirm that the extraction is via a cation exchange mechanism in the microreactor.

Solvent extraction of In3+ with microreactor from leachant containing Fe2+ and Zn2+

Abstract The microreactor has been developed for a wide range of applications because of many advantages, such as high mass transfer efficiency, low energy consumption and the closed and safe system. The application of microreactors in the traditional hydrometallurgy extraction process is expected to overcome difficulties such as co-extraction of impurities, large consumption of extractant and hidden fire risks. In this study, the extraction and separation efficiency of In3+ from a complex sulfate solution containing impurities, such as Fe2+ and Zn2+, were studied. The microreactor extraction was carried out in a Pyrex microchip, and the organic phase was prepared with the extractant di(2-ethylhexyl) phosphoric acid (D2EHPA) diluted in 260# kerosene. The results showed that with only 0.55 s contact between the organic and aqueous phases, the extraction ratio of In3+ can reach 90.80%, while only 0.16% of Fe2+ and 0.22% of Zn2+ were co-extracted; the average mass transfer speed of In3+ was calculated as high as 0.34 g·m-2·s-1. Compared with the traditional mixing settler process, microreactor extraction has advantages of higher extraction ratio of In3+, lower trend of co-extraction of the impurities and emulsification.

Optimization of Microwave Roasting for Dechlorination of CuCl Residue from Zinc Hydrometallurgy

Abstract Removal of chlorine (Cl) from the CuCl residue in the process of zinc hydrometallurgy is of great importance to improve the process economics. The current processing methods result in generation of large quantities of polluted discharge necessitating waste treatment systems. The present work attempts to de-chlorinate the CuCl residue through thermal treatment with the application of microwave energy. Relationship between explanatory and response variables was explored by response surface methodology (RSM) technique searching to optimize the dechlorination efficiency. The effect of three major parameters such as temperature, duration of heating, and particle size of samples were assessed and the optimal process conditions were identified. Analysis of variance (ANOVA) was utilized to identify the suitable model and to eliminate the insignificant model parameters. The optimized process conditions for maximizing the dechlorination efficiency are identified to be a roasting temperature of 426 °C, heating time 125 min, and particle size of samples 0.12 mm. A dechlorination efficiency of 93% could be achieved at the optimal process conditions, and validated through repeat experimental runs at the optimized process conditions. The optimized process samples are characterized utilizing XRD and SEM/EDS to validate the dechlorination efficiency.

Removal of Methylene Blue from Aqueous Solutions Using a Novel Granular Red Mud Mixed with Cement

A novel adsorbent was prepared from granular red mud (GRM) mixed with cement and its potential to be a suitable adsorbent for removal of methylene blue (MB) from aqueous solutions was evaluated. By investigating duration of oscillation, dosage of MB, pH and temperature on the adsorption effect, the best experimental condition was obtained: the methylene blue with the dosage of 150 mg/L and a constant pH of 11, after 240 minute oscillation at 303K, the removal of MB and the state balance of absorption capacity up to 86.89 % and 2.6040 mg/g. The equilibrium adsorption was found to increase with increase in temperature of the adsorption process. It was observed that the adsorption isotherms are well represented by both the Langmuir and Freundlich isotherm models. But because the Freundlich isotherm model had a better fitting, the adsorption was attributed to successive multilayer adsorption. Meanwhile, thermodynamic parameters depict the endothermic nature of adsorption and the process is spontaneous. The pseudo-second-order kinetic model was used to correlate the kinetic experimental data and the kinetic parameters were evaluated.

Ultrasound-assisted leaching of rare earths from the weathered crust elution-deposited ore using magnesium sulfate without ammonia-nitrogen pollution

The in situ leaching process of Chinas unique ion-adsorption rare earth ores has caused severe environmental damages due to the use of (NH4)2SO4 solution. This study reports that magnesium sulfate (MgSO4) as a leaching agent would replace (NH4)2SO4 by ultrasonically assisted leaching to deal with the ammonia-nitrogen pollution problem and enhance leaching process. At leaching conditions of 3wt% MgSO4 concentration, 3:1L/S ratio and 30min, the total rare earth leaching efficiency reaches 75.5%. Ultrasound-assisted leaching experiments show that the leaching efficiency of rare earths is substantially increased by introducing ultrasound, and nearly completely leached out after two stage leaching process. Thus, ultrasonic-assisted leaching process with MgSO4 is not only effective but also environmentally friendly, and beneficial to leach rare earths at laboratory scale.

Recovery of valuable metals from jarosite by sulphuric acid roasting using microwave and water leaching

ABSTRACT In this paper, jarosite residue (JR) blended with concentrated H2SO4 was subjected to a process comprising microwave roasting and water leaching. The effects of H2SO4/JR weight ratio, microwave roasting temperature and time, water leaching conditions on the recovery of Fe, Zn, In, Cu, Cd, Ag and Pb were investigated utilising a series of experiments. Based on energy conservation and environmental protection, optimum conditions for metals recovery from JR were determined as: H2SO4/JR weight ratio = 0.36, microwave roasting temperature, 250°C; roasting time, 30 min; leaching temperature, 50°C; leaching time, 1 h; and liquid–solid ratio, 4:1 (mL/g), thus, the extraction of Fe, Zn, In, Cu, Ag and Cd were 89.4, 80.7, 85.1, 90.7, 61.3 and 48.8% respectively, while the Pb was concentrated in the final residue. Scanning electron microscope-energy dispersive spectrometer (SEM-EDS) patterns were used to characterise and analyse the transformation of valuable metals in the residue after roasting and leaching.

Comparison of microwave roasting on wet/dry mixture of diasporic bauxite with alkaline: revealing the intensifying effect of H2O on chemical reaction

ABSTRACT Water is a kind of strongly microwave absorbing material. However, water is generally believed that it cannot enhance the effect of heat transfer and mass transfer of reactions at high temperature in the microwave field, due to its performance of easy drying. In this work, the intensifying effect of water on the high temperature reactions in the microwave field is proved. Specifically, the effects of different mixing methods of bauxite and alkaline, including wet mix and dry mix, on phase constitution, microstructure and leaching effect of roasting products in microwave heating process are compared. The results show that compared with the dry mixing, the wet mixing method is more benefit for forming NaAlO2 and Ca2SiO4. The roasted product of wet mix is looser and more homogeneous, which is more conducive to the subsequent leaching process. The leaching rate of Al2O3 is calculated to be 96.68% with wet mix at 800 °C and 92.58% with dry mix at 1000 °C. In addition, the mechanism of intensifying action of water on the high temperature reactions in the microwave field is discussed.

Dechlorination Mechanism of CuCl Residue from Zinc Hydrometallurgy by Microwave Roasting

Abstract Removal of chlorine (Cl) from the CuCl residue in the process of zinc hydrometallurgy is of great importance to improve the process economics. The current processing methods result in generation of large quantities of polluted discharge necessitating waste treatment systems. The present work attempts to de-chlorinate the CuCl residue through thermal treatment with application of microwave, towards which the effect of the major experimental factors such as roasting temperature, heating duration and particle size of samples on the process has been investigated. And the changes of Gibbs free energy (ΔG) of the dechlorination reactions are calculated which show that: 1) CuCl can react with H2O and air to produce CuO and HCl(g); 2) CuCl can be oxidized by air into CuO and Cl2 would be released. The tail gas chromatography, XRD and SEM-EDS analysis results of samples before and after microwave roasting verified the thermodynamics study results. Thus, the process of dechlorination by microwave roasting technology is feasible, and the tail gas can be mainly HCl(g) and air which can be absorbed with water and produce hydrochloride easily.

Ultrasound-assisted leaching of cobalt and lithium from spent lithium-ion batteries

Recovery of cobalt and lithium from spent Li-ion batteries (LIBs) has been studied using ultrasound-assisted leaching. The primary purpose of this work is to investigate the effects of ultrasound on leaching efficiency of cobalt and lithium. The results were compared to conventional leaching. In this study sulfuric acid was used as leaching agent in the presence of hydrogen peroxide. The cathode active materials from spent battery were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) before and after leaching. Effects of leaching time, leaching temperature, H2SO4 concentration, H2O2 concentration, solid/liquid ratio, and ultrasonic power have been studied. Optimal leaching efficiency of 94.63% for cobalt, and 98.62% for lithium, respectively, was achieved by using 2 M H2SO4 with 5% (v/v) H2O2 at a solid/liquid ratio of 100 g/L, and an ultrasonic power of 360 W, and the leaching time being 30 min under 30 °C. Compared with conventional leaching, the ultrasound-assisted leaching gave a higher leaching rate and improved leaching efficiency under the same experimental conditionals. The kinetic analysis of ultrasound-assisted leaching showed that the activation energy of cobalt and lithium were 3.848 KJ/mol and 11.6348 KJ/mol, respectively, indicating that ultrasound-assisted leaching of cobalt and lithium from spent LIBs was controlled by diffusion.