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The method of microwave strengthens roasting neutral leaching slag contained germanium is put forward. The dielectric properties and temperature rising behavior of neutral leaching slag in the microwave field are analyzed via experimental and theoretical analysis. The experiment used the dielectric constant test device, the microwave roasting device and the temperature measuring device. The neutral leaching slag can absorb microwave energy and transform into heat energy. The specific surface area of the calcined slag containing the neutral leaching slag is increased by microwave roasting, and the microwave energy can reduce the particle size of the mineral particles to some extent. At the same time, cracks can be seen on the surface of the calcined sand after microwave roasting. The surface of neutral leaching slag roasted by microwave reformed cracks which help to open reaction channels making the oxygen to inside takes part in oxidizing reaction significantly improving germanium oxide reaction conditions, besides increasing the leaching process of the reaction area and increasing the leaching rate. The research on the dielectric constants and temperature characteristics of neutral leaching residue can provide the theoretical and experimental basis for microwave strengthen roasting.

Uranium plant wastewater was treated in laboratory scale experiments by employing zero valent iron powder. Batch experiments conducted by the response surface methodology (RSM) proved significant decrease in concentrations of uranium due to a decrease in an oxidation-reduction potential and an increase in pH relative to an application of zero valent iron powder. Results indicated that it is effective on the removal of uranium from uranium plant wastewater with the uranium concentration of 2772.23 μg/L due to the adding of zero valent iron powder. it was found that the scope of pH is widely from 3 to 5 from the experimental data obtained in this study. The predicted model obtained from response surface methodology is in accordance with experimental results.

The waste phenolic resin was utilized as the raw material to prepare activated carbon (AC) used KOH as the activating agent via microwave heating. The phenolic resin was carbonized at 500°C and then performed with a KOH/Char ratio of 4 and microwave power of 700 W for a duration of 15 min. The physic-chemical characteristics of the AC were characterized by N2adsorption instrument, FTIR, SEM and TEM. The BET surface area and pore volume of AC were found to be 4269 m2/g and 2.396 ml/g, respectively. The activation process to generate such a phenomenally high surface area of the AC has little reported in open literatures and could pave way for preparation adsorbents that are far superior to the currently marketed adsorbents. The methylene blue (MB) was used as the model to assess its suitability to dye wastewater treatment. Towards this, the MB adsorption isotherms were conducted at three different temperatures and tested with different adsorption isotherm models. The adsorption isotherms could be modeled using Langmuir isotherm. While the kinetics could be used the pseudo-second order kinetics to describe. Thermodynamic results demonstrated that the adsorption process was a spontaneous, as well as an endothermic.

A comparison study about the extraction and separation of Cu2+and Ni2+with Lix984N in a microchannel reactor and separating funnel has been conducted. The results showed that, in the microchannel reactor, the overall volumetric mass transfer coefficient of copper was 20 times that of nickel, whereas in the separating funnel, it was only 2 times that of nickel. In addition, the separation coefficient of copper and nickel in the microchannel reactor was 5 times that of the conventional one. Typically, at initial pH=2.5, contact time 1.95 s, volume fraction of extractant Lix984N 15% and within 1.9 g l−1nickel ion concentration, the extraction rate of copper was higher than 95%, but the nickel was hardly extracted. In comparison, it needed almost 50 s to reach a Cu extraction of 95% in the separation funnel, with more than 5% Ni co-extraction rate. Although the microfluid extraction showed excellent extraction performance, there exists a need to further improve its processing capacity to apply it to industrial production. Furthermore, scaling up the microreactor has become increasingly promising under the fast developing 3D printing technology.

An effective adsorbent (Fe-La-AC) was synthesized by impregnating mixed solution ferric nitrate and lanthanum nitrate with activated carbon and heated by microwave to remove methylene blue (MB) from dye wastewater. The Fe-La-AC was characterized by N2adsorption, Fourier transform infrared spectroscopy, Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and scanning electron microscopy. Moreover, the existence of Fe3O4leads to Fe-La-AC having magnetic properties, which makes it easily separated and recycled from dye wastewater in an external magnetic field. After modification, the following phenomena occurred: Brunauer-Emmett-Teller surface area, average pore diameter, and total pore volume decreased; graphitization degree decreased. In addition, the equilibrium isotherms and kinetics of MB adsorption on raw activated carbon and Fe-La-AC were examined. The equilibrium adsorption data indicated that the adsorption behavior followed the Langmuir isotherm, and the pseudo-second-order model matched well the kinetic data. The maximum adsorption capacity of Fe-La-AC is 261.10 mg/g, which increases by 26.38% as compared with raw activated carbon. According to these results, Fe-La-AC is a promising adsorbent for the removal of MB from dye wastewater.

Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to experiment optimization of microwave drying zinc oxide leach residues (ZOLR). The effects of different factors involving temperature, drying time, material mass, material thickness and their interaction on moisture content and dehydration rate of ZOLR were investigated. Two second-order polynomial models for moisture content and dehydration rate of ZOLR were established by multivariate regression analysis. Analysis of variance shows that all independent variable and quadratic terms of the four factors have significant influence on moisture content and dehydration rate of ZOLR. The optimum drying conditions are as follows: temperature is 93.41°C, drying time is 15.9 min, sample mass is 77.91 g and material thickness is 17 mm. The predicted values of moisture content and dehydration rate were 10.98% and 1 g/min, which were close to experimental values 11±0.03% and 1±0.01 g/min under the optimal conditions. Infrared spectra analysis show that no chemical reactions took place in the process of microwave dying ZOLR and only a part of the absorbed water was removed in the sample.

In this paper, microwave regeneration of spent activated carbon saturated with organic compounds was investigated. It has been observed from the present experiments that the microwave regeneration temperature and time have significant influences on iodine adsorption value and yield of the regenerated activated carbon (RAC). The characteristics of the RAC were examined by Brunauer–Emmett–Teller (BET). The RAC has a greatly higher surface area (743.6~264.1 m2/g), total pore volume (0.54~0.22 cm3/g), and a relatively smaller average pore width (28.83~33.58 nm) compared to the spent catalyst. The separation mechanism for activated carbon and organic impurities was determined by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) equipped with an energy-dispersive spectrometer (EDS). It was a process in which the organic impurities were aggregated from the pore internal migration to the surface at low temperatures, and the organic impurities were completely decomposed as the temperature increased to 900°C for 40 min. Simultaneously, a hexagonal crystal structure material of ZnO was obtained.

The present study attempts to utilize Eupatorium adenophorumto prepare high surface area activated carbon (HSAAC) with K2CO3activation using microwave heating. The operational variables including microwave power, K2CO3/C mass ratio and heating time on the adsorption capability and yield were identified. Additionally, the surface characteristics of HSAAC were characterized by nitrogen adsorption isotherms, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The optimum conditions resulted in HSAAC with an iodine number of 1696 mg/g and a yield of 32.88%. The Brunauer-Emmett-Teller (BET) surface area and total volume were 2768 m2/g and 1.149 ml/g, respectively. The findings strongly support the feasibility for preparation of HSAAC from E. adenophorumby microwave heating.

AbstractThe 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.