The randomness of phase compositions and their distribution as well as the micro cracks and pores in refractories result in the dependence of mechanical properties on the sample size. In this work, the size effects on fracture parameters including bending strength, elastic modulus and fracture toughness of high alumina bricks were investigated by testing samples of different sizes according to the national standard in China. The results showed that the smaller samples presented higher strength, while the larger samples possessed greater elastic modulus. Weibull modulus m of bending strength for high alumina bricks calculated for samples of two sizes, each group featured 32 samples, ranged from 11 to 12, which was higher than in other refractories such as low grade high alumina, magnesia-carbon and magnesia-chrome bricks. The scatter of the average strength and its standard deviation became stable when the sample number was more than 20. The fractal dimension of fracture surface for high alumina bricks was inversely and directly proportional to the sample size and the fracture toughness, respectively. The estimated fracture toughness of high alumina bricks was close to window glass and less than alumina and mullite.
The randomness of phase compositions and their distribution as well as the micro cracks and pores in refractories result in the dependence of mechanical properties on the sample size. In this work, the size effects on fracture parameters including bending strength, elastic modulus and fracture toughness of high alumina bricks were investigated by testing samples of different sizes according to the national standard in China. The results showed that the smaller samples presented higher strength, while the larger samples possessed greater elastic modulus. Weibull modulus m of bending strength for high alumina bricks calculated for samples of two sizes, each group featured 32 samples, ranged from 11 to 12, which was higher than in other refractories such as low grade high alumina, magnesia-carbon and magnesia-chrome bricks. The scatter of the average strength and its standard deviation became stable when the sample number was more than 20. The fractal dimension of fracture surface for high alumina bricks was inversely and directly proportional to the sample size and the fracture toughness, respectively. The estimated fracture toughness of high alumina bricks was close to window glass and less than alumina and mullite.
Based on the reality of practice teaching link of environmental engineering specialty in Anhui Polytechnic University,some proposals about how to cultivate the high-quality and applied talents who major in environmental engineering were put forward,such as innovating the teaching model of theoretical courses,reforming the system of practice teaching,strengthening the professional production practice,combining course design and graduation project with practical engineering,and establishing the open laboratory.At the same time,the authors point out that all these contingency factors are aimed at reinforcing the students' practical skill and innovative competency as well as enhancing the students' employment competence.
Potential use of modified coal fly ash (MCFA) has been investigated for adsorption of organic pollutants from coking wastewater (OPs-CW).The surface morpholgy, element profile, BET specific surface area and pore size distributions of MCFA were determined.FT-IR spectrum was used to detect changes of organic functional groups in MCFA after adsorption.The results showed that when the dosage of MCFA was 2.0 g/l at pH of 6.0, 94.2% of COD removal could be achieved after 600 min of agitation at 303 K.The adsorption kinetic of OPs-CW onto MCFA was fit well to the pseudo-second order model.The intraparticle diffusion was identified not to be a sole rate limiting step, and there may also be film diffusion.Freundlich model gave a better fit to all adsorption isotherms than Langmuir.The values of E a calculated by D-R model are approximately in the range of 8-16 kJ/mol, suggesting that chemical bonding could be more likely to be the main adsorption mechanism.Negative values of ΔG° demonstrate feasibility and spontaneous nature of the adsorptive treatment.
Due to their stable chemical properties and complex structures, dyes are difficult to be removed from water. Herein, a ZIF-67/SA@PVDF (ZSA3@PVDF) mixed matrix membrane has been fabricated by incorporating silicon aerogel (SA) and zeolitic imidazolate framework material 67 (ZIF-67) nanoparticles in a polyvinylidene fluoride (PVDF) membrane for the removal and degradation of dyes from water. The influence of SA and ZIF-67 on the morphology and structure of the membrane was confirmed using scanning electron microscope (SEM) and atomic force microscope (AFM). In ZSA3@PVDF membrane, both SA and ZIF-67 are highly porous nanomaterials that possess good adsorption capacity, as confirmed by the Brunauer–Emmett–Teller (BET) result. In addition, the cobalt (Co) element of ZIF-67 can catalyze peroxymonosulfate (PMS) to generate strong oxidizing sulfate radicals (SO42−), contributing to improving regeneration capacity of the ZIF-67/SA@PVDF membrane. The water flux of ZSA3@PVDF membrane is 427.6 L m−2 h−1 bar−1, and the Methylene blue (MB) removal rate is higher than 99% when filtrating 100 mL MB solution (5 mg/L). The regeneration test result shows that the removal rate of the ZSA3@PVDF membrane is still above 98% after five cycles of adsorption of MB. The self-cleaning experiment shows that the adsorption of SA in the ZSA3@PVDF membrane promotes the catalytic performance of the membrane, showing a better self-cleaning ability. The ZSA3@PVDF membrane provides a new strategy for the removal of dyes in the advanced purification of dye wastewater.
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