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Ding H.,Tianjin University | Li J.,Tianjin University | Gao Y.,Tianjin Academy of Environmental science | Gao Y.,Tianjin United Environmental Engineering Design Company Ltd | And 5 more authors.
Powder Technology | Year: 2015

In order to reduce the release of hazardous waste silicon sludge (WSS) into the environment, we report a novel method to transform the WSS into silica nanoparticles and simultaneously to separate abrasive silicon carbide (SiC) particles. Alkali dissolution and acid precipitation processes were utilized to prepare silica nanoparticles effectively. The alkali dissolution process was carried out by sodium hydroxide to produce sodium silicate solution, from which SiC was separated by filtration. Afterward, the silica nanoparticles were prepared by acid precipitation method using hydrochloric acid. Box-Behnken design (BBD) was used to optimize the process variables affecting the dissolution efficiency, namely, mass ratio of NaOH and WSS, reaction temperature, and reaction time, and to determine the optimum conditions for the reaction process. Ultraviolet-visible spectrophotometer was used to measure the silica concentration in the solution. Characterized by XRD, FTIR, TEM, and BET surface area analysis, the silica with average pore size (10.52nm), high specific surface area (430.9m2/g) was obtained, and the particle size was about 20-45 nm. © 2015 Elsevier B.V. Source


Gao Y.,Tianjin Academy of Environmental science | Gao Y.,Tianjin United Environmental Engineering Design Company Ltd | Li X.,Tianjin University | Ding H.,Tianjin University
Waste Management | Year: 2015

A layer model was established to elucidate the mechanism of zinc removal from the metallic mixture of waste printed circuit boards by vacuum distillation. The removal process was optimized by response surface methodology, and the optimum operating conditions were the chamber pressure of 0.1 Pa, heating temperature of 923 K, heating time of 60.0 min, particle size of 70 mesh (0.212 mm) and initial mass of 5.25 g. Evaporation efficiency of zinc, the response variable, was 99.79%, which indicates that the zinc can be efficiently removed. Based on the experimental results, a mathematical model, which bears on layer structure, evaporation, mass transfer and condensation, interprets the mechanism of the variable effects. Especially, in order to reveal blocking effect on the zinc removal, the Blake-Kozeny-Burke-Plummer equation was introduced into the mass transfer process. The layer model can be applied to a wider range of metal removal by vacuum distillation. © 2015 Elsevier Ltd. Source


Fan Z.-Z.,Beijing Shengbang Tianye Technology Ltd Company | Zhao Y.-L.,Beijing Shengbang Tianye Technology Ltd Company | Zhao H.-N.,Beijing Shengbang Tianye Technology Ltd Company | Zhao H.-N.,Tianjin United Environmental Engineering Design Company Ltd | And 4 more authors.
Huanjing Kexue/Environmental Science | Year: 2014

Electrical low pressure impactor (ELPI) was used to online analyze the PM2.5 particle size and mass concentration distribution in the trapping field and ore tank of blast furnace iron-making plant. Results showed that the grain number concentration of PM2.5 in trapping field after dust removal was in the range of 105-106cm-3, and the particle size was mainly below 0.1 μm. While the grain number concentration of the PM2.5 in ore tank after dust removal was in the range of 104-105 cm-3, the particle size was mainly below 1.0 μm, and the mass concentration distribution showed a single peak. The micro-morphology of PM2.5 monomer was mainly divided into two categories, spherical particles and irregular aggregates. Chemical composition analysis indicated that the concentrations of water soluble SO4 2-, K+, Ca2+ were higher than other ions in PM2.5, with the percentage of 10.32%-28.55%, 10.36%-12.15%, 3.97%-15.4%, respectively. The major elements was Fe, Si, Al, with 16.8%-31.62%, 2.24%-8.76%, 1.24%-5.89% of total mass, respectively; organic carbon and elementary carbon were 2.7%-4.6% and 0.8%-1.3%, respectively. The emission factors of PM2.5 in trapping field and in ore tank after dust removal were ranged from 0.045 to 0.085 kg·t-1 and 0.042 to 0.071 kg·t-1, respectively. Source


Peng J.,Tianjin University | Pan J.,Tianjin United Environmental Engineering Design Company Ltd | Xu J.,Tianjin University | Zhang W.-J.,Tianjin University
Huaxue Gongcheng/Chemical Engineering (China) | Year: 2011

The ternary heterogeneous azeotropic mixture of 2-ethoxy-ethanol, 4-methyl-2-pentanone and water was theoretically studied by the residue curve maps (RCM), the residue curve, the distillation boundary and the liquid-liquid equilibrium curve. Through process design, simulating and experimental validation, the separation process was set up. Five steps that were used to get 4-methyl-2-pentanone with mass fraction of 99.24%, 2-ethoxy-ethanol with mass fraction of 99.17%, and water with mass fraction of 98.52% were designed, including azeotropic distillation, phase condensed, partial reflux of oil phase, recovery of heavy components, recovery of light components. The experimental results are highly coinciding with the simulation results, which can ensure good industrial prospects of the separation process. Source


Peng J.,Tianjin University | Pan J.,Tianjin United Environmental Engineering Design Company Ltd | Xu J.,Tianjin University | Zhang W.-J.,Tianjin University
Huaxue Gongcheng/Chemical Engineering (China) | Year: 2011

Liquid-liquid extraction, phase separation with salt, azeotropic distillation were investigated for the separation of ternary heterogeneous azeotropic mixture of 2-ethoxy-ethanol, 4-methyl-2-pentanone and water (EC+MIBK+H2O). The result shows that the results of liquid-liquid extraction were not effective; phase separation with K2CO3 as isolates has good result but a large number of salt recovery make this method too difficult to be industrialized; azeotropic distillation with methyl isobutyl ketone as entrainer can get EC with mass fraction of 99.4% and MIBK with mass fraction of 99.2%, and has perfect future for industrialization. Source

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