Shenghui Guo

Preparation of activated carbon from coconut shell chars in pilot-scale microwave heating equipment at 60 kW

Experiments to prepare activated carbon by microwave heating indicated that microwave energy can decrease reaction temperature, save the energy and shorten processing time remarkably compared to conventional heating, owing to its internal and volumetric heating effects. The above results were based on the laboratory-scale experiments. It is desirable to develop a pilot-scale microwave heating equipment and investigate the parameters with the aim of technological industrialization. In the present study, the components and features of the self-invented equipment were introduced. The temperature rise curves of the chars were obtained. Iodine numbers of the activated carbons all exceed the state standard of China under the following conditions: 25 kg/h charging rate, 0.42 rev/min turning rate of ceramic tube, flow rate of steam at pressure of 0.01 MPa and 40 kW microwave heating power after 60 kW pre-activation for 30 min. Pore structure of the sample obtained at a time point of 46 h, which contained BET surface area, and pore size distributions of micropores and total pores, was tested by nitrogen adsorption at 77K.

Microwave assisted grinding of ilmenite ore

The influence of microwave heating on the grinding of Panzhihua ilmenite ore was investigated. Factors that influence the processing are: the microwave exposure time, power density and sample mass. 40 g sample was microwave heated for 30 s with 1 kW of microwave power and followed by water quenching. SEM analysis indicated that intergranular fractures occurred between ores and gangues other than transgranular fractures after microwave treatment, which would liberate minerals from each other effectively. The subsequently magnetic separation trials provided evidence that the recovery rate increased from 44% for raw ore to 72% by microwave treatment.

Synthesis of Ag2CO3/Bi2WO6 heterojunctions with enhanced photocatalytic activity and cycling stability

Hierarchical Bi2WO6 nanoarchitectures with a size of 2–3 μm were prepared via a facile microwave-assisted solution-phase reaction process. Monodisperse spherical Ag2CO3 nanoparticles with an average size of about 10 nm were deposited onto the surface of the Bi2WO6 nanoarchitectures to form a novel Ag2CO3/Bi2WO6 heterojunction structure through a facile in situ precipitation–deposition method. The obtained samples were characterized using XRD, XPS, SEM, TEM (HRTEM), UV-vis DRS and nitrogen adsorption–desorption techniques. The photocatalytic evaluation demonstrates that the decoration with Ag2CO3 nanoparticles significantly enhances the photocatalytic activity of Bi2WO6 and the photocatalytic performance is greatly influenced by the content of deposited Ag2CO3. The 30 wt% Ag2CO3-loaded Bi2WO6 sample exhibited the highest photocatalytic activity for the degradation of rhodamine B (RhB) under visible light irradiation. Meanwhile, it also possesses excellent cycling stability and superior photocatalytic performance toward other pollutants. The dramatically enhanced photocatalytic activity and stability can be mainly ascribed to well-matched energy bands and heterojunctions between Ag2CO3 and Bi2WO6, which can effectively improve the separation of photo-induced electron–hole pairs at the heterojunction interfaces.

Controllable synthesis porous Ag2CO3 nanorods for efficient photocatalysis

The novel porous Ag2CO3 nanorods were facilely synthesized via a one-pot aqueous solution reaction at room temperature. The crystalline phase and size distribution of the nanorods were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. In addition, the porous feature of nanorods was confirmed by transmission electron microscopy (TEM) and nitrogen adsorption-desorption. The morphology and size of the Ag2CO3 crystal can be regulated via the choice of dispersing agents and adding approaches of reactants. Photocatalytic results show that the porous Ag2CO3 nanorods exhibit excellent photodegradation of rhodamine B (RhB) under visible-light irradiation, particularly the photoactivity performance and stability can be further improved in the presence of sodium bicarbonate (NaHCO3). It is indicated that NaHCO3 can prevent effectively the photocorrosion and promote the probability of electron-hole separation.

Removal of cadmium from aqueous solutions using red mud granulated with cement

Abstract A novel adsorbent was prepared from granular red mud mixed with cement and its potential to be a suitable adsorbent for the removal of cadmium ions from aqueous solutions was evaluated. The wet red mud was directly mixed up with cement at different mass fractions of 2%–8% and their properties were investigated. Based on the textural characteristics and strength, the granular red mud with 2% addition of cement maintaining for 6 d is identified to have better properties. The batch adsorption experiments for adsorption of Cd 2+ ions from solution were performed at 30, 40 and 50 °C at different initial concentrations under the condition of constant pH of 6.5. The equilibrium adsorption was found to increase with the increase of temperature during the adsorption process. Langmuir adsorption isotherm model was found to match the experimental adsorption isotherm better. The kinetics of adsorption was modeled using a pseudo second order kinetic model and the model parameters were estimated.

Dimension Optimization for Silica Sand Based on the Analysis of Dynamic Absorption Efficiency in Microwave Drying

We propose a theoretical guideline for prediction of maximum microwave absorption in microwave drying by optimizing the thickness of a silica sand layer based on analysis of reflection loss (RL). The microwave RL of the silica sand layer was studied over the moisture content of 1% to 5% at 20°C and the silica sand (5% moisture content) in the temperature range of 20 to 100°C at 2.45 GHz. The calculated RL for various moisture contents and temperatures shows that the RL sensitively depends on the thickness of the silica sand. There are absorption peaks in the RL patterns, and the microwave absorption peak shifts towards a smaller thickness side as the moisture content and temperature of the silica sand increase. We also show that the intensity of microwave absorption peaks in the RL patterns of silica sand decrease with decreasing moisture content, and achieve the highest absorption at 60°C.

Thermodynamics of leaching roasted jarosite residue from zinc hydrometallurgy in NH4Cl system

Abstract The thermal decomposition process of jarosite residue and the solubility of various oxides presented in the decomposed residue in NH 4 Cl-H 2 O system were studied. The results of heat decomposition of jarosite residue show that the insoluble ZnFe 2 O 4 phase in the residue can be decomposed at temperatures ranging from 500 °C to 650 °C for 1 h. The OLI Systems software was used to study the thermodynamics of the solubility of various metal oxides existing in the decomposed residue in NH 4 Cl-H 2 O system. The results show that the solubility of ZnO, PbO, CdO, CuO and Ag 2 O is high, while the solubility of Fe 2 O 3 is less than 10 −4 mol/L in the pH range from 4.0 to 9.0. The calculated data are in accordance with the experimental results.

Microwave-Absorbing of Carbothermic Reduced Products of Ilmenite and Oxidized Ilmenite

Abstract Microwave-absorbing characteristics of carbothermic reduction products of ilmenite and oxidized ilmenite were investigated by the method of microwave cavity perturbation and XRD. Results show that there is a great change of microwave-absorbing characteristics of reduction product from oxidized ilmenite by microwave heating at temperatures of 1000 oC, 1050 °C and 1100 °C. Microwave-absorbing characteristics of reduction products from ilmenite by microwave heating at temperatures of 1000 °C and 1050 °C become strong, the increasing of diffraction intensity of the characteristic peak of FeTi2O5 from 850 CPS to 1250 CPS is the main reason for the great change of microwave-absorbing characteristics of reduction products in the temperature range of 1000 C-1050 °C. Microwave-absorbing characteristics of reduction product from ilmenite by microwave heating is greater than that of reduction product from oxidized ilmenite by microwave heating.

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 preparing V2O5 by calcination from ammonium metavanadate using response surface methodology

Parameters of technique to prepare vanadium pentoxide by calcination from ammonium metavanadate were optimized using central composite design of response surface methodology. A quadratic equation model for decomposition rate was built and effects of main factors and their corresponding relationships were obtained. The results of the statistical analysis show that the decomposition rate of ammonium metavanadate is significantly affected by calcination temperature and calcination time. The optimized calcination conditions are as follows: calcination temperature 669.71 K, calcination time 35.9 min and sample mass 4.25 g. The decomposition rate of ammonium metavanadate is 99.71%,which coincides well with experimental value of 99.27% under the optimized conditions, suggesting that regressive equation fits the decomposition rates perfectly. XRD reveals that it is feasible to prepare the V2O5 by calcination from ammonium metavanadate using response surface methodology.