Silicon
·
2020
·Vol. 13
·期 2
·531-541
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IF 1.499
Li Feifei,Jiang Xuesong,Zuo Qiuxia,Li Jingwei,Ban Boyuan,Chen Jian
Iron is a major impurity in quartz sand and must be strictly removed in many applications. However, the iron removal rate in most of the conventional purification process is not high enough. In this study, a fast, low-energy consuming, environment-friendly and simple process for purifying quartz is demonstrated by a combination of microwave heating and ultrasound-assisted acid leaching treatment. Using the characteristics of selective heating of microwave, the micro-inclusions burst and generate cracks in the surrounding quartz matrix far below the α/β phase transition temperature, which enables removal of the impurities in the subsequent processing steps and reduces iron diffusion into the quartz matrix. Microwave process sequence, time, and temperature are all important factors, and appropriate parameters need to be explored. Ultrasound can assist acid leaching removal of Fe impurities through the cracks. Under optimized conditions, the iron content can be reduced to below 0.167 ppmw with one single purification pass.
研究领域:
材料科学
·
环境工程
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产品关联
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2024
·
IF 5.2
Yusufujiang Mubula,Mingming Yu,Hongju Gu,Lei Wang,Man Chen,Tingsheng Qiu,Guangjun Mei
Rare earth molten salt electrolytic slag (RMES) has emerged as a promising secondary resource for rare earth elements (REEs). This study introduces an innovative leaching technique for extracting REEs from RMES under atmospheric conditions, employing an alkali phase reconstruction method followed by an acid leaching process. Additionally, the external electric field was employed to enhance the reaction. Under the optimal reaction conditions: NaOH initial concentration of 70 wt%, NaOH-slag mass ratio of 4:1, temperature of 160 °C, current density of 1000 A/m 2 , reaction time of 90 min, stirring speed of 300 r/min, HCl concentration of 4 mol/L, liquid-solid ratio of 15:1, and leaching time of 20 min, the leaching efficiencies of Nd and Pr reach up to 99.21% and 99.14%, respectively. Phase analysis indicates that the rare earth fluorides transform into rare earth hydroxides, significantly enhancing their solubility in acid solution. The imposition of an external electric field leads to pronounced disruption of the RMES surface, thereby promoting the formation of stable reactive oxygen species in the alkaline medium. This facilitates the decomposition of fluorinated rare earths and hastens the phase reconstruction, resulting in an enhanced leaching process. The achieved leaching efficiency with an external electric field is 37% higher than that without an electric field.
研究领域:
冶金工程
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材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
Journal of Cleaner Production
·
2025
·
IF 10
Chenyu Wang,Han Zhou,Chaoyue Wu,Weibo Sun,Xiaohui Sun,Chao He
Hydrothermal carbonization combined with wet chemical methods for treating sewage sludge produce valuable hydrochar and phosphorus. However, further investigation is needed to optimize the balance among phosphorus recovery, heavy metal leaching, residual hydrochar utilization to enhance overall process benefits. In this study, acid leaching on hydrochar was conducted using HCl, H 2 SO 4 , citric acid at 0.1 – 1.0 M acid concentration for 10 – 1440 min, the liquid-to-solid ratio between 50 to 500 mL/g. Employing single-factor experiments, response surface methodology, various characterization techniques, the impacts of acid leaching on the leaching rates of phosphorus and heavy metals, along with residual rate and properties of the remaining hydrochar, were quantitatively assessed. The results indicate leaching parameters directly impact the phosphorus leaching rate. HCl and H 2 SO 4 achieve their corresponding maximum phosphorus leaching rate within 60 min at acid concentration 0.5 M, liquid-to-solid ratio 500 mL/g, while using citric acid requires 360 min. When H 2 SO 4 is used as the extractant, the corresponding maximum phosphorus leaching rate can be maintained within a wider leaching time and acid concentration range. A moderate acid concentration, prolonged leaching time, higher liquid-to-solid ratio lead to increased levels of heavy metal concomitant leaching. Compared to HCl and citric acid, using H 2 SO 4 as extractant results in lower heavy metal leaching and lower sensitivity to leaching parameters. The residual rates of hydrochar range from 59.3% to 77.3%, with H 2 SO 4 and HCl as extractant yielding higher residual rates than citric acid. The properties of the remaining hydrochar were altered by acid leaching, resulting in a decrease in specific surface area and pore number, but an increase in oxygen-containing functional groups and calorific value, which affects its subsequent utilization. Finally, based on the aforementioned results and potential process scenarios, the selection of optimal acid leaching parameters was discussed. The results provide reference for the selection of phosphorus recovery and resource utilization pathway based on sludge-derived hydrochar.
研究领域:
环境科学
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资源与能源工程
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DOI
高影响因子
CHEMICAL PAPERS
·
2018
·Vol. 72
·期 12
·2997-3003
·
IF 0.963
Guo Dongqing,Fu Likang,Wang Shixing,Zhang Libo,Peng Jinhui
A new purification method for molybdenum disulfide via NaNO 3 –HCl–HNO 3 synergistic leaching at 80 °C was developed. The effects of the concentration of NaNO 3 , HCl, and HNO 3 , and liquid–solid ratio and the leaching time on the purification of molybdenum disulfide were investigated by orthogonal array design methodology. The results of Taguchi method utilizing L 25 (5 5 ) orthogonal array indicated that the NaNO 3 concentration had the greatest impact on the purification of molybdenum disulfide. The optimum conditions for the purification of molybdenum disulfide were as follow: concentration of NaNO 3 = 2.5%, concentration of HCl = 11%, concentration of HNO 3 = 1.0%, liquid–solid ratio = 3, and the leaching time = 10 h. Under optimum conditions, the content of molybdenum increased from 55.1 to 59%, and the contents of iron, copper, lead, and calcium decreased from 0.35 to 0.21%, 0.027 to 0.008%, 0.054 to < 0.005%, and 0.27 to 0.035%, respectively. Based on molecular formula of molybdenum disulfide, the content of molybdenum disulfide increased from 91.93 to 98.44%. XRD and SEM indicated that this method removed only the impurities and did not affect the phase and particle size of molybdenum disulfide. The results show that the new purification method avoids the roasting process and will achieve the “green” production. The new method based on orthogonal array is effective for the purification of molybdenum disulfide via acid leaching.
研究领域:
材料科学
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化学工程
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产品关联
DOI
高影响因子
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