Preparation of ultrafine silica from potash feldspar using sodium carbonate roasting technology

A novel process was developed for the preparation of ultrafine silica from potash feldspar. In the first step, potash feldspar was roasted with Na_2CO_3 and was followed by leaching using Na OH solution to increase the levels of potassium, sodium, and aluminum in the solid residue. The leaching solution was then carbonated to yield ultrafine silica. The optimized reaction conditions in the roasting process were as follows： an Na_2CO_3-to-potash feldspar molar ratio of 1.1, a reaction temperature of 875°C, and a reaction time of 1.5 h. Under these conditions, the extraction rate of SiO_2 was 98.13%. The optimized carbonation conditions included a final solution p H value of 9.0, a temperature of 40°C, a CO_2 flow rate of 6 m L/min, a stirring intensity of 600 r/min, and an ethanol-to-water volume ratio of 1：9. The precipitation rate and granularity of the SiO_2 particles were 99.63% and 200 nm, respectively. We confirmed the quality of the obtained ultrafine silica by comparing the recorded indexes with those specified in Chinese National Standard GB 25576―2010.

Microemulsion leaching of vanadium from sodium-roasted vanadium slag by fusion of leaching and extraction processes

The fusion of the leaching and purification processes was realized by directly using microemulsion as the leaching agent.The bis-(2-ethyhexyl)phosphoric acid(DEHPA)/n-heptane/NaOH microemulsion system was established to directly leach vanadates from sodium-roasted vanadium slag.The effect of the leaching agent on the leaching efficiency was investigated,in addition to the molar ratio of H_(2)O/NaDEHP(W),DEHPA concentration,solid/liquid ratio,stirring time,and leaching temperature.In optimal situations,the vanadium leaching efficiency reaches 79.57%.The X-ray diffraction characterization of the leaching residue and the Raman spectrum of the microemulsion before and after leaching demonstrate the successful entry of vanadates from the sodium-roasted vanadium slag into the microemulsion.The proposed method successfully realizes the leaching and purification of vanadates in one step,thereby greatly reducing production costs and environmental pollution.It also offers a new way to achieve the green recovery of valuable metals from solid resources.

New technique of comprehensive utilization of spent Al_2O_3-based catalyst

A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roasting temperature of 750℃ and roasting time of 30 min, molar ratio of Na2O to Al2O3 of 1.2, the leaching rates of alumina, vanadium and molybdenum in the spent catalyst are 97.2%, 95.8% and 98.9%, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by precipitators A and B, and the precipitation rates of vanadium and molybdenum are 94.8% and 92.6%. Al（OH）3 was prepared from sodium aluminate solution in the carbonation decomposition process, and the purity of Al2O3 is 99.9% after calcination, the recovery of alumina reaches 90.6% in the whole process; the Ni-Co concentrate was leached by sulfuric acid, a nickel recovery of 98.2% and cobalt recovery over 98.5% can be obtained under the experimental condition of 30% H2SO4, 80℃, reaction time 4 h, mass ratio of liquid to solid 8, stirring rate 800r/min.